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Biology and Cultural Control of Lesser Cornstalk Borer on Sugarcane

Permanent Link: http://ufdc.ufl.edu/UFE0041472/00001

Material Information

Title: Biology and Cultural Control of Lesser Cornstalk Borer on Sugarcane
Physical Description: 1 online resource (179 p.)
Language: english
Creator: Sandhu, Hardev
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: biology, briere, burnt, compensation, damage, dead, development, elasmopalpus, green, harvesting, lesser, life, population, reproductive, sugarcane, tillage, varieties
Entomology and Nematology -- Dissertations, Academic -- UF
Genre: Entomology and Nematology thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy BIOLOGY AND CULTURAL CONTROL OF LESSER CORNSTALK BORER ON SUGARCANE By Hardev Singh Sandhu May 2010 Chair: Gregg S. Nuessly Major: Entomology and Nematology Lesser cornstalk borer, Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae), is an important sugarcane pest in southern Florida. It feeds on meristematic tissues of young sugarcane shoots and causes dead hearts, symmetrical rows of holes in the leaves, and plant death. Development and survivorship of immature stages, and reproductive, generation and population life table parameters of E. lignosellus were studied on sugarcane at nine constant temperatures. Development times were shortest between 27 and 30 degreeC. Lesser cornstalk borer required 543.5 degree days to complete development ranging from 22.8 plus or minus 0.3 d at 33 degreeC to 120.7 plus or minus 2.8 d at 13 degreeC. Pre- and post-oviposition periods decreased and oviposition period increased with increasing temperatures from 13 degreeC to 33 degreeC. Mean fecundity, stage-specific survival (lx), stage-specific fecundity (mx), intrinsic rate of increase (r), and net reproductive rate were greatest at 30 degreeC. The relationships between developmental rate and temperature, and between temperature and r, were best fit by the Briere-1 and -2 models, respectively. A 2-year greenhouse experiment was conducted to document variety and age specific E. lignosellus feeding damage and yield effects in sugarcane larvae. Sugarcane response to feeding was recorded as damage symptoms, tiller production, number of millable stalks, and sugarcane and sucrose yield. Infestation at 3-leaf stage resulted in more dead hearts and dead plants than when infested at 5- and 7-leaf stages. The sugarcane variety CP89-2143 was more sensitive to E. lignosellus damage and resulted in reduced sugarcane and sucrose yield compared with CP78-1628 and CP88-1762. All varieties infested at the 3-leaf stage produced more yield than when infested at the 7-leaf stage. Comparison of yield reduction with the E. lignosellus lethal damage (dead hearts + dead plants) showed these varieties had equal ability to compensate for feeding damage, but that compensation ability declined with the delay in infestation time. Field studies were conducted in 2006 to determine the effects of harvest residue from green harvesting versus pre-harvest burning on E. lignosellus damage and sugarcane yield. Harvest residue removed from a green harvested field and placed in plots in a plant cane field resulted in significant reduction of E. lignosellus damage. Sugarcane (TCA) and sucrose (TSA) yields did not differ between plots with and without harvest residues in plant or ratoon sugarcane. Three post-harvest tillage levels were tested in green and pre-harvest burned fields in 2008 and 2009. Significantly less E. lignosellus damage was observed in green versus pre-harvest burned fields in both years. No- and intermediate-tillage significantly reduced damage compared to conventional tillage in green harvested fields only. In both years, greater TCA was produced in intermediate than other tillage levels in green harvested sugarcane, whereas TCA and TSA were greater in conventional than other tillage levels in pre-harvest burned sugarcane. These studies provide information useful for E. lignosellus population prediction and discovered the variety and age specific nature of sugarcane damage by this pest. Field studies showed the positive effects of green harvesting and intermediate tillage for reducing E. lignosellus damage and increasing sugarcane yield.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Hardev Sandhu.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Nuessly, Gregg S.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041472:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041472/00001

Material Information

Title: Biology and Cultural Control of Lesser Cornstalk Borer on Sugarcane
Physical Description: 1 online resource (179 p.)
Language: english
Creator: Sandhu, Hardev
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: biology, briere, burnt, compensation, damage, dead, development, elasmopalpus, green, harvesting, lesser, life, population, reproductive, sugarcane, tillage, varieties
Entomology and Nematology -- Dissertations, Academic -- UF
Genre: Entomology and Nematology thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy BIOLOGY AND CULTURAL CONTROL OF LESSER CORNSTALK BORER ON SUGARCANE By Hardev Singh Sandhu May 2010 Chair: Gregg S. Nuessly Major: Entomology and Nematology Lesser cornstalk borer, Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae), is an important sugarcane pest in southern Florida. It feeds on meristematic tissues of young sugarcane shoots and causes dead hearts, symmetrical rows of holes in the leaves, and plant death. Development and survivorship of immature stages, and reproductive, generation and population life table parameters of E. lignosellus were studied on sugarcane at nine constant temperatures. Development times were shortest between 27 and 30 degreeC. Lesser cornstalk borer required 543.5 degree days to complete development ranging from 22.8 plus or minus 0.3 d at 33 degreeC to 120.7 plus or minus 2.8 d at 13 degreeC. Pre- and post-oviposition periods decreased and oviposition period increased with increasing temperatures from 13 degreeC to 33 degreeC. Mean fecundity, stage-specific survival (lx), stage-specific fecundity (mx), intrinsic rate of increase (r), and net reproductive rate were greatest at 30 degreeC. The relationships between developmental rate and temperature, and between temperature and r, were best fit by the Briere-1 and -2 models, respectively. A 2-year greenhouse experiment was conducted to document variety and age specific E. lignosellus feeding damage and yield effects in sugarcane larvae. Sugarcane response to feeding was recorded as damage symptoms, tiller production, number of millable stalks, and sugarcane and sucrose yield. Infestation at 3-leaf stage resulted in more dead hearts and dead plants than when infested at 5- and 7-leaf stages. The sugarcane variety CP89-2143 was more sensitive to E. lignosellus damage and resulted in reduced sugarcane and sucrose yield compared with CP78-1628 and CP88-1762. All varieties infested at the 3-leaf stage produced more yield than when infested at the 7-leaf stage. Comparison of yield reduction with the E. lignosellus lethal damage (dead hearts + dead plants) showed these varieties had equal ability to compensate for feeding damage, but that compensation ability declined with the delay in infestation time. Field studies were conducted in 2006 to determine the effects of harvest residue from green harvesting versus pre-harvest burning on E. lignosellus damage and sugarcane yield. Harvest residue removed from a green harvested field and placed in plots in a plant cane field resulted in significant reduction of E. lignosellus damage. Sugarcane (TCA) and sucrose (TSA) yields did not differ between plots with and without harvest residues in plant or ratoon sugarcane. Three post-harvest tillage levels were tested in green and pre-harvest burned fields in 2008 and 2009. Significantly less E. lignosellus damage was observed in green versus pre-harvest burned fields in both years. No- and intermediate-tillage significantly reduced damage compared to conventional tillage in green harvested fields only. In both years, greater TCA was produced in intermediate than other tillage levels in green harvested sugarcane, whereas TCA and TSA were greater in conventional than other tillage levels in pre-harvest burned sugarcane. These studies provide information useful for E. lignosellus population prediction and discovered the variety and age specific nature of sugarcane damage by this pest. Field studies showed the positive effects of green harvesting and intermediate tillage for reducing E. lignosellus damage and increasing sugarcane yield.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Hardev Sandhu.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Nuessly, Gregg S.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041472:00001


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BIOLOGY AND CULTURAL CONTROL OF LESSER CORNSTALK BORER ON SUGARCANE By HARDEV SINGH SANDHU A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORID A IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010 1

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2010 Hardev Singh Sandhu 2

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To my beloved parents, Mr. Joginder Singh and Mrs. Kulwant Kaur for their perpetual love and support and to my wife, Sandeep Sandhu for encouragement and understanding 3

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ACKNOWLEDGMENTS First and foremost, I would like to thank Dr. Gregg S. Nuessly, my doctoral committee chair, who provi ded excellent guidance, graduat e training, motivation, unconditional support and trust to complete this project. He has mentored me throughout my doctoral studies, and his insight and guidance were essential in the completion of this dissertation. In addition, I would like to thank my committee members Dr. Susan E. Webb (Entomology and Nematology department) for pr oviding laboratory facilities to complete biology studies and also for her helpful f eedback and suggestions, Dr. Ronald H. Cherry (Everglades Research and Eduaction Center) fo r providing valuable suggestions for the improvement in writing resear ch papers which became the part of this dissertation, and Dr. Robert A. Gilbert (EREC) for graciously agreeing to f ill the outside member position on my committee and for critical review of manuscripts and valuable suggestions. I owe my sincere thanks to Drs. J. L. Capinera (Entomology and Nematology department) and K. Pernezny (EREC) for provid ing laboratory facilities for insect diet preparation. My special thanks to University of Florida extens ion agents Dr. R. Rice and L. Baucam, and L. Davis for their great hel p in finding research fields. I am deeply indebted to N. Larsen, M. Gonzalez, F. Sosa, J. Terry G. Goyal, and B. Thappa (EREC) for assistance in moth collection, help in green house and field experiments. My sincere thanks to Drs. M. Brennan and J. Colee (Statist ic department), and Drs. M. Josan and T. Lang (EREC) for assistance with statistics. I am extremely thankful to Sugar C ane Growers Cooperative of Florida and United States Sugar Corporation for provid ing funding for this study, and land for collecting insects and sugarcane. This work was made possible by student financial 4

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support from the Wedgworth Gra duate Fellowship and the Univ ersity of Florida College of Liberal Arts and Sciences. I profoundly thank my parents for all of their encouragement throughout my graduate studies. I would not be who I am and I would not have accomplished this work without their immense love and support. I have no words to thank my wife, Sandeep Sandhu for always being there for me, for encouraging me when frustration occurred, for always staying positive, and for her unconditional love. Finally, I would like to thank almighty god to bless me with courage and patience for this whole study period. 5

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TABLE OF CONTENTS page ACKNOWLEDG MENTS..................................................................................................4 LIST OF TABLES............................................................................................................9 LIST OF FI GURES ........................................................................................................11 ABSTRACT ...................................................................................................................13 CHAPTER 1 REVIEW OF LITERATURE....................................................................................16 Introducti on.............................................................................................................16 Insect Pests and Sugarcane...................................................................................17 Systematics and Distribution of Lesser Cornst alk Bore r.........................................18 Description and Li fe Cycle......................................................................................19 Eggs .................................................................................................................19 Larvae ..............................................................................................................21 Pupae ...............................................................................................................23 Adults ...............................................................................................................24 Longevity and Reproducti ve Beha vior..............................................................25 Fecundity..........................................................................................................25 Generation Time...............................................................................................27 Number of G eneratio ns....................................................................................27 Abiotic Factors Affe cting Development...................................................................28 Temperat ure.....................................................................................................28 Soil Mois ture.....................................................................................................28 Host Pl ants.............................................................................................................30 Plant Damage by Lesser Cornstalk Borer...............................................................30 Peanuts ............................................................................................................30 Corn.................................................................................................................31 Sorghum ...........................................................................................................32 Soybea n...........................................................................................................32 Sugarc ane........................................................................................................ 32 Control Strategies...................................................................................................33 Cultural Co ntrol.......................................................................................................34 Planting Time...................................................................................................34 Cultivat ion.........................................................................................................34 Irrigatio n...........................................................................................................35 Destruction of Al ternate Ho sts..........................................................................35 Fertilizat ion.......................................................................................................36 Green Harves ting.............................................................................................36 Chemical C ontrol....................................................................................................36 6

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Peanuts ............................................................................................................37 Corn.................................................................................................................38 Cowpeas and Southern P eas...........................................................................39 Sugarc ane........................................................................................................ 39 Biological C ontrol....................................................................................................40 Sampli ng.................................................................................................................41 Research Goals ......................................................................................................42 2 TEMPERATURE-DEPENDENT DEVELOP MENT OF LESSER CORNSTALK BORER, ELASMOPALPUS LIGNOSELLUS (LEPIDOPTERA: PYRALIDAE) ON SUGARCANE UNDER LABORA TORY CONDI TIONS...........................................49 Introducti on.............................................................................................................49 Materials and Methods............................................................................................50 Insect Colony Maintenanc e..............................................................................51 Production of Sugar cane Plant s.......................................................................51 Laboratory Temperature De velopmental Studies .............................................52 Developmental Rate and Ma thematical Models...............................................54 Data Anal ysis...................................................................................................56 Result s....................................................................................................................56 Laboratory Temperature De velopmental Studies .............................................56 Model Eval uation..............................................................................................58 Discussio n..............................................................................................................59 Laboratory Temperature De velopmental Studies .............................................59 Model Eval uation..............................................................................................60 3 LIFE TABLE STUDIES OF LESSER CORNSTALK BORER, ELASMOPALPUS LIGNOSELLUS (LEPIDOPTERA: PYRALID AE) ON SU GARCANE......................76 Introducti on.............................................................................................................76 Materials and Methods............................................................................................77 Reproductive Parameters.................................................................................77 Life Table Pa rameters......................................................................................78 Model Eval uation..............................................................................................79 Data Anal ysis...................................................................................................79 Result s....................................................................................................................80 Reproducti on....................................................................................................80 Life Table Pa rameters......................................................................................81 Model Eval uation..............................................................................................81 Discussio n..............................................................................................................82 Reproducti on....................................................................................................82 Life Table Pa rameters......................................................................................83 Model Eval uation..............................................................................................83 Model Applic ation.............................................................................................84 Conclusi on..............................................................................................................85 7

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4 COMPENSATORY RESPONSE OF SUGARCANE TO ELASMOPALPUS LIGNOSELLUS DAMAGE....................................................................................101 Introducti on...........................................................................................................101 Materials and Methods..........................................................................................103 Production of Sugar cane Plant s.....................................................................104 Insect Rear ing................................................................................................104 Experiment Design.........................................................................................105 Damage Asse ssment.....................................................................................106 Sugarcane Yield Assessment .........................................................................106 Data Anal ysis.................................................................................................107 Results ..................................................................................................................107 Damage ..........................................................................................................107 Tiller Produ ction.............................................................................................110 Sugarcane Yield Traits...................................................................................110 Discussio n............................................................................................................114 Damage ..........................................................................................................114 Tiller Produ ction.............................................................................................115 Sugarcane Yield Traits...................................................................................117 Conclusion s..........................................................................................................118 Future Direc tions..................................................................................................119 5 EFFECTS OF HARVEST RESI DUE AND TILLAGE LEVEL ON ELASMOPALPUS LIGNOSELLUS DAMAGE TO SUGARCANE .........................128 Introducti on...........................................................................................................128 Materials and Methods..........................................................................................131 Experimental Design......................................................................................131 Damage Asse ssment.....................................................................................134 Sugarcane Yield Assessment .........................................................................135 Data Anal ysis.................................................................................................135 Results ..................................................................................................................136 Effects of Crop Age a nd Trash Bl anket..........................................................136 Effects of Harvesting Method and T illage....................................................... 138 Discussio n............................................................................................................141 Effects of Crop Age a nd Trash Bl anket..........................................................141 Effects of Harvesting Method and T illage....................................................... 143 Conclusi on......................................................................................................145 6 SUMMARY ...........................................................................................................155 LIST OF REFE RENCES.............................................................................................165 BIOGRAPHICAL SKETCH ..........................................................................................178 8

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LIST OF TABLES Table page 1-1 Known host plants of Elasmopalpus lignosellus (Zeller)....................................45 2-1 Developmental models and their mat hematical equations tested to describe the relationship between temperatur e and development of lesser cornstalk borer on s ugarcane. ...........................................................................................63 2-2 Mean ( SEM) developmental times (d ) by temperature for egg through pupal stages of lesser cornstalk borer on sugar cane under laboratory conditions.......64 2-3 Mean ( SEM) developmental time (d) by temperature for lesser cornstalk borer larval instars on sugarc ane under laboratory conditions ...........................65 2-4 Mean ( SEM) percentage survival by temperature of lesser cornstalk borer immature stages under l aboratory condi tions.....................................................66 2-5 Parameters from linear regression of developmental rate and temperature for lesser cornstalk borer on sugarca ne under laboratory conditions .......................66 2-6 Fitted coefficients and evaluation indices for si x non-linear developmental models of lesser cornstalk borer dev elopmental rate on sugarcane...................67 3-1 Mathematical equations of devel opment models tested to describe the relationship between temperature and intrin sic rate of natural increase (r) of E. lignosellus on sugar cane................................................................................87 32 Analysis of variance for effects of temperature, cohort and generation on reproductive parameters of E. lignosellus on sugar cane....................................88 3-3 Mean ( SEM) pre-oviposition, ovi position, post-oviposition periods and fecundity of E. lignosellus on sugarcane under labor atory condi tions................89 34 Analysis of variance for effects of temperature, cohort and generation on life table parameters for E. lignosellus on sugar cane...............................................90 3-5 Life table parameters of E. lignosellus on sugarcane at nine constant temperat ures ......................................................................................................91 3-6 Fitted coefficients and ev aluation indices for six no n-linear models tested to describe the relationship between intrin sic rate of natural increase (r) of E. lignosellus and temper ature...............................................................................92 3-7 Life table parameters for Pyralidae (Lepidoptera) pests on artificial diet and lesser cornstalk borer on s ugarcane in th is study...............................................93 9

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4-1 Analysis of variance of year, vari ety, leaf stage and their interactions on percentage E. lignosellus damage to sugarca ne in 2008 and 2009.................120 4-2 Mean ( SEM) percentage E. lignosellus damage to sugarcane pooled across 2008 and 2009......................................................................................121 4-3 Analysis of variance effects on tiller s, millable stalks, sugarcane yield, and sucrose yield per bucke t during 2008 and 2009...............................................122 4-4 Mean ( SEM) tiller production and yield traits per bucket in 2008...................123 4-5 Mean ( SEM) tiller production and yi eld traits per bucket in 2009...................124 4-6 Change in tiller production and yield traits in response to lethal damage (dead hearts + dead plants) caused by E. lignosellus in 2008. .........................125 4-7 Change in tiller production and yield traits in response to lethal damage (dead hearts + dead plants) caused by E. lignosellus in 2009. .........................126 5-1 Analysis of variance of crop age, harvest residue and their interaction on E. lignosellus and other pests damage to sugarc ane, and sugarcane yield traits in 2006 ..............................................................................................................146 5-2 Mean ( SEM) percentage of E. lignosellus and other pests damage to sugarcane in 2006............................................................................................147 5-3 Mean ( SEM) yield traits in crop age, harvest residue, and their interactions in 2006 ..............................................................................................................148 5-4 Analysis of variance of harvesting method, tillage level and their interaction on E. lignosellus and other pests damage to sugarcane in 2008 and 2009.....149 5-5 Mean ( SEM) percentage damage by E. lignosellus and other pests to sugarcane in 2008............................................................................................150 5-6 Mean ( SEM) percentage damage of E. lignosellus and other pests to sugarcane in 2009............................................................................................151 5-7 Analysis of variance of harvesting me thod, tillage level, and their interaction on sugarcane yield trai ts in 2008 and 2009 ......................................................152 5-8 Mean ( SEM) sugarcane yield traits by harvesting method, tillage level and their interaction in E. lignosellus -infested fields during 2 008............................153 5-9 Mean ( SEM) sugarcane yield traits by harvesting method, tillage level and their interaction in E. lignosellus -infested fields during 2 009............................154 10

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LIST OF FIGURES Figure page 2-1 Larval, pupal and adult stages of le sser cornstalk borer: A) Larva (sixth instar), B) Pupa, C) Adul t male, D) Adult fema le................................................69 2-2 Experimental set-up for lesser corn stalk borer larval development on young sugarcane shoots: A) Upr ooted sugarcane plants, B) Seed pieces removed, C) Paper towel wrapped around the plant base and kep moist, D) Five shoots placed in each plastic container with a layer of vermi culite under neath.............70 2-3 Relationship between egg developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on s ugarcane. ...........................................................................................71 2-4 Relationship between larval developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on s ugarcane. ...........................................................................................72 2-5 Relationship between prepupal developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on s ugarcane. ...........................................................................................73 26 Relationship between pupal developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on s ugarcane. ...........................................................................................74 2-7 Relationship between total (egg deposition to adult emergence) developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstal k borer on s ugarcane. ...........................75 3-1 Relationship between the temperat ure (C) and age-specif ic survival, lx (solid line), and age specific daily fe cundity, mx (dashed line), for E. lignosellus at the tested temperatures. A) 13 C, B) 15 C, C) 18 C, D) 21 C, E) 24 C, F) 27 C, G) 30 C, H) 33 C, I) 36 C ...........................................94 3-2 Relationship between temperature (C) and intrinsic rate of natural increase (r) for E. lignosellus with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimat ed by Briere-2 model aT(T T0) ((Tm T) (1/d)) for E. lignosellus on sugarcane...................................................................99 11

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3-3 Predicted population growth of E. lignosellus on sugarcane based on the Briere-2 model and average monthly te mperatures at two locations in southern Flor ida................................................................................................100 4-1 Lesser cornstalk borer damage in s ugarcane: A) Larva coming out of silken tunnel, B) Larval entry site in the plant, C) Dead heart, D) Holes in the leaves. ..............................................................................................................127 12

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Abstract of Dissertation Pr esented to the Graduate School of the University of Florida in Partial Fulf illment of the Requirements for t he Degree of Doctor of Philosophy BIOLOGY AND CULTURAL CONTROL OF LESSER CORNSTALK BORER ON SUGARCANE By Hardev Singh Sandhu May 2010 Chair: Gregg S. Nuessly Major: Entomology and Nematology Lesser cornstalk borer, Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae), is an important sugarcane pest in southern Flor ida. It feeds on meristematic tissues of young sugarcane shoots and causes dead hearts, symmetrical rows of holes in the leaves, and plant death. Development and survivorship of immature stages, and reproductive, generation and populati on life table parameters of E. lignosellus were studied on sugarcane at nine cons tant temperatures. Devel opment times were shortest between 27 and 30 C. Lesser cornstalk borer required 543.5 degree days to complete development ranging from 22.8 0.3 d at 33 C to 120.7 2.8 d at 13 C. Preand post-oviposition periods decreased and ovip osition period increased with increasing temperatures from 13 C to 33 C. Mean fecundity, stage-specific survival (lx), stagespecific fecundity (mx), intrinsic rate of increase (r) and net reproductive rate were greatest at 30 C. The relationships between developmental rate and temperature, and between temperature and r, were best fit by the Briere-1 and -2 models, respectively. A 2-year greenhouse experiment was c onducted to document variety and age specific E. lignosellus feeding damage and yield effects in sugarcane larvae. Sugarcane response to feeding was recorded as damage symptoms, tiller production, 13

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number of millable stalks, and sugarcane and sucrose yield. Infestation at 3-leaf stage resulted in more dead hearts and dead plants than when infested at 5and 7-leaf stages. The sugarcane variety CP89-2143 was more sensitive to E. lignosellus damage and resulted in reduced sugarcane and sucrose yield compared with CP78-1628 and CP88-1762. All varieties infested at the 3leaf stage produced more yield than when infested at the 7-leaf stage. Comparison of yield reduction with the E. lignosellus lethal damage (dead hearts + dead plants) showed t hese varieties had equal ability to compensate for feeding damage, but that compensation abili ty declined with the delay in infestation time. Field studies were conducted in 2006 to det ermine the effects of harvest residue from green harvesting versus pre-harvest burning on E. lignosellus damage and sugarcane yield. Harvest residue removed from a green harvested field and placed in plots in a plant cane field resulted in significant reduction of E. lignosellus damage. Sugarcane (TCA) and sucrose (TSA) yields di d not differ between plots with and without harvest residues in plant or ratoon sugarcane Three post-harvest tillage levels were tested in green and pre-harvest burned fields in 2008 and 2009. Significantly less E. lignosellus damage was observed in green versus pre-harvest burned fields in both years. Noand intermedi ate-tillage significantly reduced damage compared to conventional tillage in green har vested fields only. In bot h years, greater TCA was produced in intermediate than other tillage levels in green harvested sugarcane, whereas TCA and TSA were greater in conv entional than other tillage levels in preharvest burned sugarcane. 14

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These studies provide information useful for E. lignosellus population prediction and discovered the variety and age specific nat ure of sugarcane damage by this pest. Field studies showed the posit ive effects of green harvesti ng and intermediate tillage for reducing E. lignosellus damage and increasing sugarcane yield. 15

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CHAPTER 1 REVIEW OF LITERATURE Introduction Sugarcane, Saccharum officinarum L. is an important crop grown in many southern temperate through tropica l regions of the world. Br azil is the worlds leading sugarcane producer followed by India (U SDA 2008). Florida, Louisiana, Texas and Hawaii are the main sugarcane producing states in the U.S. Florida is the leading sugarcane producing state in the U.S. with 401,000 acres of sugarcane valued at $398.9 million dollars in 2008 (USDA 2008). In Florida, sugarcane is mainly grown in the Everglades Agricultural Area around Lak e Okeechobee. Due to the lakes warming effect, sugarcane is protected from severe winter and frost conditions. Sugarcane is a tall-growing monocotyledonous crop plant of the family Poacae that is cultivated primarily fo r its ability to store high conc entrations of sucrose in the stem internodes. Cox et al. (2000) reported that modern sugarcane varieties cultivated for sugar production are complex interspecific hybrids ( Saccharum spp.). These hybrids have arisen through intensive select ive breeding of species within the Saccharum genus, primarily involving crosses between the species Saccharum officinarum L. and S. spontaneum L. Daniels and Roach (1987) reported that Polynesia was the S. officinarum center of origin. The species was probably transported throughout Southeast Asia by humans, leading to a moder n center of diversity in Papau, New Guinea and Irian Jaya, Indonesia, where the majority of specimens were collected in the late 1800s. Commercial sugarcane is propagated vegetat ively. Germination refers to the initiation of growth from buds present on the planted sets or on the stems of the stools 16

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that remain in the soil after harvest of the previous crop (Wilkox et al. 2000). Sugarcane varieties differ in their sensitivity to temper ature, but in general germination is slow at soil temperatures below 18C and increases rapidly up to about 35C. Maturation is associated with the lower rainfall and cooler temperatures of the winter months (Bull 2000). Insect Pests and Sugarcane There are several factors that can result in decreased sugarcane yield, including insect damage. Worldwide, sugarcane as an agro-ecosystem is inhabited by many insect species in both above ground (aer ial) and below ground (subterranean) habitats (Meagher 1996). He reported the important aerial pest species in the following orders and families: Orthoptera (Acridoidea), Homoptera (Aphididae, Cercopidae, Coccidae, Delphacidae, Diaspididae, Pseudococci dae and Margarodidae) and Lepidoptera (Castniidae, Crambidae, Noctuidae, and Pyralidae). He also reported the subterranean sugarcane insect pests represented by Orthoptera (Gryllidae and Gryllotalpidae), Isoptera (Mastotermitidae, Rhinotermitidae, and Termitidae), Heteroptera (Cicadidae, Cydnidae, Tingidae), Coleoptera (Curculionidae, Elat eridae, and Scarabaeidae), Hymenoptera (Formicidae), and Diptera (S tratiomyidae) (Meagher 1996). Common insect pests of sugarcane in Florida are west Indian cane weevil, Metamasius hemipterus sericeus (Oliver) (Coleoptera: Curc ulionidae), white grub, Ligyrus subtropicus Blatchley (Coleoptera: Scarabaeidae), wireworms Melanotus communis (Gyllenhal) (Coleoptera: Elater idae), sugarcane lace bug, Leptodictya tabida (HerrichSchaeffer) (Heteroptera: Tingi dae), white sugarcane aphid, Melanaphis sacchari (Zehntner) (Homoptera: Aphidae) yellow sugarcane aphid, Sipha flava (Forbes) 17

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(Homoptera: Aphidae), sugarcane borer, Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), and lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) (Nuessly 2006). Systematics and Distribution of Lesser Cornstalk Borer The lesser cornstalk borer was first described by Zeller in 1848 as Pempelia lignosella from material collected in Brazil and Uruguay, and a single female from Carolina, United States. Its seasonal and geographical distribution was recorded by Zeller (1872) from Brazil and Colombia, in S outh America, and Caro lina and Texas, in the United States. He also added the description of two varieties, incautella and tartarella, based on the color variations. Later on in 1881, he placed incautella as a synonym of lignosella though still retaining tartarella as a valid variety. Blanchards 1852 work confused the status of the species by placing it within a new genus, Elasmopalpus, and giving it the species name E. augustellus The systematics of lesser cornstalk borer becam e more complicated in 1888 when it was redescribed as Dasypyga carbonella by Hulst (1888) based on specimens collected in Texas, USA. Hulst (1890) later rectified this mistake and placed D. carbonella as a synonym of P. lignosella tartarella In the same publication, he redescribed lignosellus and placed it in genus Elasmopalpus for the first time, giving a bibliography and notes on the distribution and seasonal occurrence. The synonymy, then, stands as follows: Pempelia lignosella Zeller, Elasmopalpus augustellus Blanchard, Pempelia lignosella tartarella Zeller, Pempelia lignosella incautella Zeller, Dasypyga carbonella Hulst, Elasmopalpus lignosellus (Zeller) Hulst, Elasmopalpus lignosellus incautellus (Zeller) Hulst, Elasmopalpus lignosellus tartarellus (Zeller) Hulst. 18

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The lesser cornstalk borer is widely distri buted in the tropical through temperate regions of the New World, in cluding Hawaii and the southern half of the United States from California to the Caro linas, north on the east coast to Massachusetts, and south through Central and South America to Argentina, Chile, and Peru (Heinrich 1956). It is a polyphagous pest attacking large numbers of crops, including corn, peanuts, field peas, beans, soybeans, wheat, barley, oats, rice cotton, cowpeas, nurseries of forest trees, and sugarcane (Luginbill and Ainslie 1917, Heinrich 1956, Harding 1960, Leuck 1966, Falloon 1974, and Dixon 1982). Lesser cornstalk borers first record as an economic pest was in 1878 in the United States (Riley 1882). Outbreaks of lesser cornstalk borer on sugarcane were reported by Plank (1928) in Cuba, Wolcott (1948) in Puerto Rico, and Ingram et al. (1951) in Florida (USA). In Jamaica, it was first reported to attack sugarcane in 1959 and since then it has been recognized as a potentially se rious pest of sugarcane (Bennett 1962). Description and Life Cycle Lesser cornstalk borer is holometabolous in sect. It has well defined egg, larval, pre-pupal, pupal and adult stages. The review of the description and biology of E. lignosellus is summarized below by stage. Eggs Egg size, color and duration varied among host plants and researchers. Luginbill and Ainslie (1917) reported the egg to be ovate, circular in cross section, 0.67 mm high and 0.46 mm wide. Egg color was greenish white on first deposition, then turned to pinkish and finally crimson with a tinge of ye llow near eclosion. Duration of egg stage was 6 to 8 d when larvae were reared on cowpeas. Dupree (1965), working on lesser cornstalk borer on southern peas, reported th e same physical description as Luginbill 19

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and Ainslie (1917), but with eggs white to pal e yellow initially and then later to deep orange or red. The eggs were 0.5 mm high and 0.4 mm wide. The duration of egg stage was 2.4 d. Leuck (1966) reported on soybean that the eggs were ovate, 0.61 0.01 mm high and 0.37 0.01 mm wide. Egg color was white when first deposited, changed to pink and finally to crimson red. The duration of egg stage was 4 d. Stone (1968) reported the color of sterile eggs was either creamish or red at one end only. He used this distinction to separate the sterile eggs from fertile eggs. Similarly, Simmons and Lynch (1990) reported the first deposited (i.e., sterile) eggs as pale green in color. The location of egg deposition varied among host plants. Eggs on soybean and southern peas were deposited singly, underside t he leaves, on the stem, at the base of the pebbles on soil, and in the exposed sand y soil (Leuck 1966). In sorghum, eggs were deposited in the soil up to the depth of 2 mm and within a 10 cm diameter around the plant (Reynolds et al. 1959) In peanuts, King et al. (1961) reported the majority of eggs in the soil around the plant base with some eggs deposited on the lower stems. Smith et al. (1981) reported that 93.8% of eggs were deposited below the soil surface, 6.1 % on the soil surface, and 0.07% on the peanut plant. Hori zontally, 50% eggs were deposited within 5.08 cm r adius of the plant and 29% in the next 5.08 cm radius with some deposition as far as 23 cm from plants. Nearly 83.5% of the eggs were laid under the drip line. In corn, Knutson (1976) reported the eggs scattered on the surface of loose, dry soil as compared to compact, wet soil. Eggs were not concentrated near the corn plants. On soybean, eggs were deposited on the top and bottom sides of leaves, all over the stem, and in expos ed sandy soil and at the base of the pebbles on the soil. Smith and Ota (2002) reported th e eggs were deposited on or near the base of stalks in 20

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sugarcane. On cowpea, Luginbill and Ainslie (1917) reported that eggs were deposited on plant stems, leaf axils and in the soil near the base of plants. Temperature was found to affect duration of the egg stage and size of the eggs produced by females. Leuck and Dupree (19 65) found that the egg stage lasted 428 hr at 18 C, but only 52 hr at 33 C. Carbonell ( 1977), working in Jamaica, West Indies in sugarcane, reported the minimum size of eggs ranged from 0.33 to 0.455 mm (mean of 0.352 mm), and the maximum size ranged fr om 0.55 to 0.706 mm (mean of 0.593 mm), depending upon the temper ature conditions. Larvae The head of the larvae is slightly bilobed, flattened, highly polished dark brown, and with a triangular clypeus (Lug inbill and Ainslie 1917). The cervical shield is almost straight in front, but much rounded behind. All thoracic and abdominal (except the terminal) segments are slightly swollen. The number of larval instars, and durat ion of larval development varies by temperature and food host. Elasmopalpus lignosellus passes through four (summer) to six (fall) larval instars, depending upon the tem perature (Luginbill and Ainslie 1917). They reported the duration of larval st age on cowpeas ranged from 15.6 to 16.9 d, depending upon the te mperature. Larval coloration and size also was affe cted by crop host. Length and width for instars I to VI were 1.7 and 0.23 mm, 2. 7 and 0.29 mm, 5.7 and 0.44 mm, 6.9 and 0.61 mm, 8.8 and 0.89 mm, 8.8 and 0.89 mm, respectively (Luginbill and Ainslie 1917). Dupree (1965) used fresh foli age and stem sections of seedling southern peas to feed the larvae individually in 15 44 mm vials. He reported that larvae were yellowish green, with reddish pigmentation dorsally, and transverse bands that formed in their 21

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early instars. Longitudinal stripes star ted to develop and bec ame well pronounced instar V. Mature larvae were bluish green, but tended towards reddi sh brown with fairly distinct yellowish stripes dorsally. The head capsule width for larvae on southern peas was 0.200, 0.307, 0.460, 0.644, 0.883 and 1. 300 mm for larval instars I to VI, respectively. Duration of larval instars was 4.2, 2.9, 1.4, 3.1, 2.9, and 8.8 d for instars I, II, III, IV, V and VIth, respectively, with m ean larval duration of 33 d. Larval length ranged from 1.8 mm in instar I to 13 mm instar VI. Leuck (1966) placed the cloth cover having eggs on it, between two soybean leav es. Upon emergence, the first instar larvae crawled onto the leaves and fed. Following larv al emergence, the larvae and leaves were transferred to a 3.78 L jar with 5 cm layer of fine, white, dry sand at the bottom. He reported the head capsule widths fo r instars I to VI as 0.19 0.01, 0.31 0.01, 0.46 0.01, 0. 65 0.02, 0.86 0.2 and 1.12 0.01 mm, respectively. The duration of instars I to VI was 2.6 0.2, 1.8 0.2, 1.8 0.2, 2.0 0. 3, 2.8 0.6 and 8.6 0.5 d, respectively, with total larval durat ion of 13 to 24 d. Mean head capsule width was 0.19 0.01, 0.31 0.01, 0.46 0.01, 0.65 0.02, 0.86 0.2 and 1.12 0.01 mm respectively for instars I to VI. Chalf ant (1975) used modified pinto bean base diet with a fine vermiculite layer over the diet. He poured the diet into 30 ml plastic medicine cups, followed by a 2 to 4 mm layer of autoc laved fine vermiculite. He put five newly emerged larvae in each cup and covered the cup with a polyethylene lid. This diet is considered to be the most effective larval diet available and is used in most of the published research work on lesser cornstal k borer. Carbonel l (1977) used young shoots of sugarcane to feed the larvae in a gl ass jar. He report ed the mean length of instars I to VI instars as 1. 46, 2.92, 4.95, 7.84, 10.46, 14.36 mm, respectively. Length 22

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and width of head capsule for instars I to VI was 0.240 and 0.190, 0.342 and 0.334, 0.517 and 0.507, 0.786 and 0.724, 0.905 and 0.890, 1.223 and 1.193 mm, respectively. Larvae developed to the pupal stage in 30.33 d feeding on sugarcane. Pupae The pupa is pale green, with yellowish abdo minal segments initially, later on whole body becomes brown and finally turns to uniform black color (Luginbill and Ainslie 1917). A row of six hooked spines, arranged tran sversely, is present on the tip of the abdomen. The terminal abdominal segment is round on male pupa and irregular on female pupa. On southern peas, Dupree (1 965) reported that pupation occured below the soil surface encased in a cocoon with a sand coating. On soybean, Leuck (1966) reported pupation in an oval case constructe d from sand and silk at the end of one of the larval tunnels beneath the soil. Size and duration of the pupal stage va ried by crop and temperature. On cowpeas, Luginbill and Ainslie (1917) reported the pupa to be 8.1 mm long and 2 mm wide. The length of pupal stage was reported to be variable depending upon the temperature. Pupal development varied from 7 to 11 d in July, 7 to 10 d in August, 8 to 18 d in September through October, and 19 to 21 d in October through November. Dupree (1965) reported that pupae raised on southern peas were 8 mm in length and 2 mm in diameter. The pupal period ranged from 7 to10 d (mean of 9.0 d) in 1957 and 8 to10 d (mean of 8.7 d) in 1958. Leuck ( 1966) reported the durat ion of pupal stage ranged from 7 to11 d (m ean of 10.0 0.4 d) for male s and 9 to13 d (mean of 10.4 0.4 d) for females raised on soybeans, with an over all pupal duration of 10 .2 0.8 d. He also reported the variation in pupal period with change in temperature. Pupal period ranged from 3 to 24 d depending upon the maxi mum air temperature ranged from 26.5 23

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to 35.7 C and minimum air tem perature ranged from 14.1 to 26.6 C during this period. Pupal period was more at lo w temperature and decreased with increase in temperature. Carbonell (1978) reported t hat the pupal stage lasted an average of 10.96 d on sugarcane in Jamaica, West Indies. Adults Adults are linear shaped moths (Luginbill and Ainslie 1917). Their narrow forewings are folded over the dorsal and lateral sides of the body in resting position. Sexes can be easily differentiat ed from the forewing color. The female has uniformly dark brown or carbon black colored forewin gs, while males have light brown colored forewings margined with dark brown color. Wing expanse was reported as 17 mm to 25 mm by Luginbill and Ainslie (1917) and 15 to 18 mm by Carbonell (1977). Leuck (1966) reported that the moths are nocturnal. During daytime they rest under foliage of the host plants (soybean and southern peas) and made short jerky flights when disturbed. Darkness, still air, low humidity and warm temperature were the favorite conditions for adult ac tivity. One-third of female s caught in 15 W black light traps were mated and capabl e of producing eggs. Mati ng and egg deposition occurred during dark period especially before midnight. Various solutions have been used to f eed adults, including sucrose solution (8% by Chalfant 1975, 2% by Stone 1968), 50% honey with sodium benzoate (Dupree 1965), and 10% honey (Leuck 1966). Mean adult longevity was 11.4 d and 17.9 d for males and 14.5 and 19.5 d for females duri ng the first and second study years, respectively (Dupree 1965). Mean ovipos ition period was 7.8 d (range 1 to18 d). Luginbill and Anslie (1917) r eported that oviposition period on cowpeas was 10.4 d (range 7 to 14 d) with the majority of eggs deposited before midnight. 24

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Longevity and Reproductive Behavior More detailed information on longevity and reproductive behavior and output was determined from detailed laboratory studies by Stone (1968). Mated males in laboratory colonies could be distinguish ed from unmated males by the presence of transparent versus tanslucent seminal fluid for at l east 5 d after mating (Stone 1968). Females had full size eggs in the calyx and lateral or common oviducts within 1 to 2 d after emergence. Stone (1968) reported mating in most of the cases from 0140 to 0640 hr and egg deposition from 1900 to 2100 hr. Average mating time was 102 min with approximately equal mating frequency at all male:fe male sex ratios fr om 1:1 to 1:4. Mating was more likely to occur in fed than in unfed moths. Moths mated equally through 1 to 6 d and the pre-oviposition peri od was approximately 2.8 d. The mean oviposition period was report ed to be 11.8 d (range 7 to 19 d) Mean longevity was 24.2 1.5 d in mated males and 18.1 1.7 d in ma ted females. Longevity of virgin females was roughly twice as long as for mated females. In other studies, the mean oviposition period was reported to be 10.4 d (Luginbill and Ainslei 1 917), 11.8 d (Stone 1968), and 6.4 d (Simmons and Lynch 1990) on artifici al diet. Dupree (1965) and Leuck (1966) reported a mean ovipos ition period of 4.1 d (ranging from 1 to 9 d) and 4.7 d, respectively on soybean. After rearing the larvae on artificial diet, Chalfant (1975) reported average longevity of 5 d in females and 8 d in males. He also observed that adults preferred rough surface for ovipositi on within cages. Blue-colored Handi-Wipes (disposable paper towel) was found to be the preferred surface for egg laying. Fecundity Fecundity varied by host plant and diet. On cowpeas, the fecundity was reported to be 91 to 342 eggs/female with a mean of 192 eggs (Luginbill and Ainslei 1917). King 25

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et al (1961) reported 124 eggs / female on peanuts. On sout hern peas, Dupree (1965) recorded 11 to 261 eggs / female in 1957 and 5 to 221 eggs / female in 1958. On soybean, 2 to 314 eggs / female with a mean of 125.7 20.5 eggs were reported by Leuck (1966). Stone (1968) reported 293 to 562 eggs / female with a mean of 419.5 14.7 eggs when larvae reared on artificial diet and eggs were layed on cheese cloth. On sugarcane, Carbonell (1978) reported 125.3 eggs / female. Mack and Backman (1984) reported an incr ease in fecundity with increase in constant temperature from 17 to 27.5 C, peaked at 27.5 and 30.5 C. Fecundity was greatly reduced when adults were kept at a temperature of 17 or 35 C. They concluded that, this 3-fold increase in numbe r of eggs deposited at 5-fold faster rate might be the reason of outbreaks in hot and dry weather. Mack and Backman (1986) later studied the effect of fluc tuating diel temperature on longev ity and oviposition. They found that females held in hot day/cool night (8.7 2.2 eggs / day) or very hot day / warm night (13.9 4.3 eggs / day) had significantly higher oviposition rates than females held at cool day/hot night (4.3 1.8 eggs / day) cycles. Simmons and Lynch (1990) studied the performance of lesser cornstalk borer adults feed on eight different diets, including, two honey solution diets, sucrose solution, gatorade, three beer diets and water. Adults longevity (24.9 d), mean ovipositional period (6.4 d) and fecundity (180 eggs per female) were highest on 8.3% sucrose solution followed by 10% honey solution and yeast. They also pointed out that the adult longevity ranged from 7 to 9 d to 38 to 42 d depending upon the occurrence of mating and fed or not fed. Well fed, unmated adults lived longer than unfed, mated adults. 26

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Generation Time Life cycle from egg to adult was completed in 38.5 d for the spring generation, and 64.6 d for the fall generation under unspecified laboratory conditions, feeding larvae on cowpeas (Luginbill and Ainsli e 1917). Sanchez (1960) repor ted a life cycle of 24.3 d during August and 46.3 d during September th rough October by feeding peanut roots to larvae under laboratory conditions. Eggs were exposed to 21.1 to 37.8 C while larvae were exposed to the following daily minimu m and maximum temperatures: August, 26.4 and 34.7 C; September, 23.3 and 31.7 C. Pupae were exposed to temperature ranges in August, 18.9 to 38.9 C; September, 17.8 to 36.7 C. Dupree (1965) reported a life cycle of 47.8 d and 55 d during June-S eptember in 1957 and 1958, respectively, by feeding larvae on foliage and stem sections of seedling southern peas. Temperature range was 19.2 to 30.2 C in 1957 and 19.3 to 31.2 C in 1958. Leuck (1966) recorded a life cycle of 32.8 2.8 d by feeding la rvae on soybean or cowpea leaves under laboratory conditions. Monthly mean mini mum temperature ranged from 14.1 to 22.6 C, monthly mean maximum ranged from 26.5 to 35.7 C. Stone (1968) reported 24 to 28 d generations by feeding the larvae on modifi ed Burgers (wheat ge rm base) artificial diet. Carbonell (1978) report ed that lesser cornstalk borer completed its life cycle in 52.43 d by rearing the larvae on sugarcane. Number of Generations The number of generations varies depending on the location, temperature, crops and cropping season. There were four generat ions per year reported in Colombia, South Carolina, USA (Luginbil l and Ainslie 1917). In a normal cropping season of soybeans and cowpeas in southern Georgia, USA (early June through early November), there were three and a partial fourth generation of lesser cornstalk borer (Leuck 1966). 27

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Abiotic Factors Affecting Development Abiotic factors play important in role development of cold-blooded animals like insects. The temperature and soil moisture are important abiotic factors which affect the development and survival of lesser cornst alk borer. The effect s of temperature and soil moisture on lesser cornstalk borer population are discussed below. Temperature Overwintering is the phenomenon of passing the colder part of the year by prolonging the growth period when the temperature is t oo low to hamper the normal development. Larvae or pupae are believed to be the overwintering stages on cowpeas in South Carolina, USA (Luginbill and Ainslie 1917). King et al. (1961) revealed larvae and pupae present in old peanut fields as late as December, but absent from January to April. Prolonged duration of larval and pupal stages due to low temperatures in winter helped the lesser cornstalk bor er in overwintering. Leuck (1966) reported the pupae, situated under leafy debris and on the soil su rface, was the predominant overwintering stage. Holloway and Smith (1976) indicated that there was a drastic increase in the duration of larval, pre-pupal and pupal stages with a 6 to 7 C reduction in temperature. They didnt report any diapa use development due to alteration in temperature and photoperiod. Soil Moisture Soil moisture is one of the primary factor effecting lesser cornstalk infestation and development (King et al. 1961, Leuck 1966, French 1971, Knutson 1976, Mack and Backman 1984, Mack et al. 1988, and Smith and Ota 2002). King et al. (1961) reported that lesser cornstalk borers we re more injurious to peanuts during dry years, and larval mortality appeared to be greater during wet seasons. Irrigation seemed to reduce larval 28

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populations in some fields. Leuck (1966) r eported an increase in lesser cornstalk borer populations during periods of high summer temperatures, because conditions were optimum for mating and egg deposition. Si milarly, Mack and Backman (1984) reported 98% of egg deposition on the soil surface when the soil was dry and 55% when the soil was wet. When the soil was wet, more larvae came out of their silken tunnels and were exposed to predators. French (1971) reported that major losses o ccurred due to lesser cornstalk borer on peanuts during years with a moistu re deficit for part of or the entire gro wing season. Knutson (1976) reported more parasitism in pl ots covered by rain. In laboratory, he reported higher mortality repor ted in the larvae reared in soil having 100% water holding capacity than dry soil. Mack and Appel (1986) repor ted that, in hot and dry conditions, the maximal daily temperatures in the so il layer can exceed 48 C, with soil moisture levels of -5 to -20 bars but lesser corn stalk borer larvae, pupae and adults were adapted to this hot, xeric environment as evidenced by their low cuticular permeabilities and their tolerance of body water losses up to 43%. In continuation with this Mack et al. (1988) reported high mortality due to body water losses in common predators of lesser cornstalk borer like Geocoris punctipes (Say) nymphs (69.4%) and adults (80.6%), Reduviolus roseipennis (Reuter) adults (58.1%) and especially Solenopsis invicta Buren workers (100%) as compared to lesser co rnstalk borer larvae (17%) and pupae and adults (0%). Increased mortalit y of predators and better survival in hot xeric conditions resulted in the outbreaks of lesser cornstalk borer. In Hawaii, Smith and Ota (2002) reported that prompt irrigation application was the most ef ficient practice to control lesser cornstalk borer. 29

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Host Plants Lesser cornstalk borer is a polyphagous pest with very wide host range. Common and scientific names for known plant hosts are provided in Table 1-1. Lesser cornstalk borer larvae feed on both grasses and broad-l eaved plants, many of which are weeds that provide alternatives to crop plants within treated fields. Plant Damage by Lesser Cornstalk Borer In general, lesser cornstalk borer damages y oung plants or fruits in contact with (i.e., bean pods) or developing be neath the soil (i.e., peanut). Larvae enter plants at or just below the soil surface. Feeding damage that causes the death of the growing point in grasses results in a condition calle d dead heart. Larvae form silken tunnels from entrance hole out into the soil in which they rest and molt between feeding. Young leaves in grasses and sedges slightly damaged by larvae below the soil line, but above the growing point, expand from the terminals to display rows of holes. Peanuts In peanuts, feeding was mostly restricted to plant parts that were contiguous to soil or no more than 4 cm deep. Any part of the plant which touches the ground is attacked by the larvae which construct silken tunnels in contact with the plant. Larvae bore into small stalks at soil level and tunnel upwards. Attacked plants either dry up quickly in hot dry weather or break in the wind. Fifth and sixth instar E. lignosellus are reported to be voracious feeders and caused heavy damage to the crop by quick mining in plants (Dupree 1964). Leuck (1966) re ported outbreaks in soybeans and cowpeas associated with field stress, e.g. drought and late plant ing. Leuck (1967) described two types of lesser cornstalk borer larval feeding damage to Early Runner peanut plants. The first two instars fed on leaves, veget ative bud and flower axils, and slightly scarified ground 30

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level stems. The remaining instars fed on and in pegs and pods. The latter type damage was considered to be potentially the most damaging. Smith et al. (1975) recorded that in Spanish peanuts larvae c aused the damage by scarifying the tissue destined to become inflorescences and cons uming flower buds concentrated in the crown area. Most of the dam age was caused in the plant reproductive stage. Smith and Holloway (1979) recorded the economic inju ry level for Starr peanuts to be 14,448 larvae/ha while Mack et al. (1988) reported it to be 3.63 to 5.44 larvae per row meter. There was 9.87 kg/ha yield reduction for every 1% increase in infested plants (Berberet et al.1979). Pods in early stages of devel opment (1 to 3 stage s) were preferred and severely attacked than the pods in latter stages (4 to 6 stages) of peanuts. Damage to more mature pods was caused by older larv ae, but this damage was primarily external scarification (Lynch 1990). Mack et al. (1988) reported more pod and seed damage in R5 stage and at the higher densities of lesser cornstalk borer. Huang and Mack (1989) extracted residues from various plant parts of peanut to see the phagostimulative effect on lesser cornstalk borer larv ae. Residues from pods and leaves were found to be more attractive than roots, pegs, lower st ems and higher stems. Injury caused by feeding of lesser cornstalk borer on peanut pl ants resulted in infestation by fungus Sclerotium rolfsii Sacc. causing southern stem rot (Wolf et al.1997). Carbondioxide released from underground plant parts of peanut s was reported to be the attractant for lesser cornstalk borer la rvae (Huang and Mack 2001). Corn Young larvae attacked the plants at collar region or slightly below the soil surface and resulted in a symmetrical pattern of holes on the unfurling leaves. Plants can overcome this damage or they may be partially stunted. Ol der larvae bored into the 31

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stem of the plant and caused dead hearts (All and Gallaher 1977). The heading above shows that if you have a subheading of a cert ain level, you must have more than one. The rationale is that you cannot have a list of only one item. Sorghum Larval stages of lesser cornstalk borer were sampled in the upper soil habitat during different growth st ages of grain sorghum (Funder burk et al. 1986). Samples revealed that the first gener ation occurred on vegetative stage while second and third generations were present on reproductive stage of the crop. No other published reports were found on lesser cornstalk borer damage to sorghum. Soybean Braxton and Gilreath (1988) r eported that the lesser cornstalk borer bored into the plant stem and killed the plant s. They recorded 41% damage in young plants compared to only 10% in older plants showing more susceptibility of younger plants to lesser cornstalk borer attack. Soft stem tissues of young plan ts may be the reason of easy penetration of lesser cornstalk borer which resulted in heavy damage. Sugarcane Sugarcane can be harvested either by burning or without burning before harvesting. If sugarcane is not burnt bef ore harvesting, then it leaves sugarcane residue or trash after harvesting and also known as green harvesting. Outbreaks in sugarcane are associated with post-harvest burning (Plank 1928). Wolcott (1948) stated that most severe out breaks in Puerto Rico occurred in areas where trash had been burned. Trash burnt field had severe damage caused by lesser cornstalk borer. So non-burning of trash was recommended as a preventive measure in Florida sugarcane (Ingram et al. 1951). Bennett (1962) recorded outbreaks in Jamaica, 32

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Barbados, and St. Kitts and concluded that fields burned after harvest generally suffered heavier attacks than those burned befor e harvest. He also suggested about olfactory stimulus provided by burning attracted gravid moths to the area but the trash blanket provided unfavorable conditions for ov iposition. Metcalfe (1966) in Jamaica reported the attraction of mo ths to bare ground for ovipositi on within 24 hours of a trash fire. In sugarcane, the larvae bore into the stem of young cane sprouts at or just below the soil surface. The larvae then tunnel upw ards in the plant and cause dead hearts by feeding on the tissues and killing the growi ng point. One larva can kill 5 to 7 shoots during its period of development. Genera lly the peak damage occurred 2 to 3 weeks after harvesting in the stubble cane (Schaaf 1974). Carbonell (1 978) observed that E. lignosellus attacked the sugarcane during the firs t 3 months of its growth period and caused dead hearts that were very similar to that caused by Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). He also reported that all the attacked plants were not killed but there was a recovery of some plants to normal growth. There was 27.84 % recovery in plant canes and 48.06 % re covery in stubble canes. Hence stubble canes had more potential to recover from the damage as compared to plant canes. Delay in growth of the recovered canes was more in stubble canes than plant canes. Control Strategies Due to sub-terranean nature and excellent protection by t he silken tunnels, its hard to control this pest with a single control strategy. By using a combination of two or more control strategies, the chances to control it will be more. Cult ural controls that prevent infestation are more effective than control af ter infestation of lesser cornstalk borer. Several cultural practices have been evaluated to prevent the infestation and to control this pest. 33

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Cultural Control Planting Time Luginbill and Ainslei (1917) recommended late fall or early winter sowing after freeing the fields from all crop residues as t he best practice for preventing infestation. Early planting of corn and sorghum was s uggested to enable the plants to get a good start before heavy infestation occurs. Ea rly season planting and pre-planting weed control were reported be the effi cient methods to control lesser cornstalk borer (All et al. 1979). Cultivation Disking field borders and terraces to stir the ground and break up the winter quarters of the pupae were encouraged by Luginb ill and Ainslei (1917). Thorough land preparation was recommended by Isley and Miner (1944) and Cowan and Dempsey (1949). On fall beans, Isley and Miner (1944) suggested that inspection of underground parts of previous crop to determine whether a thorough soil preparation was necessary in order to kill half grown larvae. They bel ieved that larvae from eggs deposited after planting would not have enough time to develop to destructive size before the plants passed the most susceptible stage of grow th. Cowan and Dempsey (1949) observed a reduction in lesser cornstalk borer damage to pimiento in thoroughly tilled land compared to conservation tillage. Dupree ( 1964) reported that fallow land kept for 8-10 weeks before planting resulted in significant reduction of borer damage in peanuts and soybean. Cheshire and All (1979) reported the difference in behavior of larvae on corn in no-tillage and conventionalt illage cultural practices. Greenhouse flats (50 35 8 cm) with sandy loam soil were used for all tr eatments. In no-tilla ge field having wheat and rye residues, the number of attacked pl ants was only 4 as compared to 22 in 34

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conventionaltillage. They concluded that mulch residues in notillage crop provided an alternate food source resultin g in reduced damage to the corn. Irrigation As hot and dry conditions are favorable for lesser cornstalk borer, irrigation is very important method of cont rol. In case of crops which were planted flat like sorghum, timely flood irrigation gave promising results in lesser cornstalk borer control. In some susceptible crops, sow the crop at the bottom of irrigation furrow and fill the furrow with water during serious infestation. The ar ea between the plant rows may be furrowed out at a later date for irrigation when the plants are larger (Reynolds et al. 1959). Smith and Ota (2002) reported that prompt irrigation application was the most efficient practice to control lesser cornstalk borer. They also poi nted out that due to damage in early growth stage, any agronomic practice which can enh ance the early growth of sugarcane will enable it to outgrow the susceptible stage quickly. Irrigation reduced the damage by 63.2% in corn (All and Gallaher 1977). Destruction of Alternate Hosts Pulling and destroying all infested crop plants was recommended by Watson (1917). Box (1929) recommended er adication of barnyard grass, Echinochloa crusgalli from sugarcane fields in Cuba as a met hod of control. Clean cultivation was recommended by Stahl (1930) in strawberries. Larvae migrating from other plant hosts were the main source of crop infestation in California. Destructi on of infested alternate hosts in the field some weeks prior to planting was considered to be an important cultural practice to control lesser cornstalk borer (Reynolds et al. 1959). 35

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Fertilization Fertilization of sandy areas stimulates growth and makes plants more resistant (Luginbill and Ainslei 1917). Stuckey (1945) reported a two-third r eduction of infested cowpea plants when nitrogen, phosphorus, and potassium fertilizers were used, as compared to non-fertilized plots. Similarly Bissell (1946) reported less infestation of lesser cornstalk borer in cowp eas with use of fertilizers. Green Harvesting The field of sugarcane which was bur nt before harvesting had severe damage caused by lesser cornstalk borer. So non-burning of trash was recommended as a preventive measure in Florida sugarcane (I ngram et al. 1951). Similar observations were taken by Bennett (1962) on sugarcane in Jamaica, West Indies. In sugarcane, Hall (1999) conducted a trial with trash blanket and without tr ash blanket in stubble cane field. He reported that onl y 0.5 % shoots were killed by lesser cornstalk borer in the field with trash blanket as compared to 7. 0 % shoots killed in fi elds without trash blanket. Chemical Control Many authors have come to the conclusion that the lesser cornstalk borer is difficult to control with insecticides (Arthur and Arant 1956, Reynold et al. 1959, Harding 1960 and Chalfant 1975). Many of these materials are no longer labeled for use on these or any other crops. In nursery-gro wn Arizona cypress seedlings, Chlorpyriphos 2.5% granules applied at 2.24 kg AI/ha during planting and midseason reported to be most effective (Hyche et al. 1984). Isle y and Miner (1944) obtained unsatisfactory control beans with applic ation of calcium arsenate and cryolite to the lower surfaces of the leaves and to the stems of bean plants agai nst migrating larvae in Kansas. Kulash 36

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(1948) reported some contro l on snap beans with 3% lindane pl us 5% DDT dust at the rate of 11.35 kg/ha, and with 60 g of 50% DDT wettable powder in one gallon of water per 15 m of crop row, applied to the base of the plants. Peanuts In peanuts, there was no significant incr ease in yield if DDT, BHC, chlordane, toxaphene or aldrin dusts were applied in the drill prior to planting, but there was significant increase in yield when aldrin, diel drin (2.27 kg AI/ha) or toxaphene (6.8 kg AI/ha ) granules applied to soil surface at the time of peggi ng (Arthur and Arant 1956). Granular endrin, SD-4402 and parathion at 567 g/ha and DDT at 1134 g/ha were reported to be the most effect ive insecticides in reducing the larval damage to pegs and nuts. The spray forms of t hese insecticides at 18.9 to 189.3 L/ha under the pressure of 2110 to 2815 g/cm2 obtained were equally effe ctive (Harding 1960). Sanchez (1960) conducted control experiments on peanut s with DDT, endrin, azinophosmethyl, mevinphos, and chlorothion sprays and with dust applications of endrin, dieldrin, heptachlor, DDT, and toxaphene. None of thes e treatments gave significant control. Mack et al. (1989) reported chlorpyriphos 10G at 2.2 kg AI/ha to be more effective if applied during flowering or pegging than at planting. Hot dry weather during the growing period in Alabama reduced the re sidues and efficacy of the chemical as compared to in Florida. Length of effe ctiveness after application was highest with chlorpyriphos (19 to 67 d) followed by f onofos (25 to 28 d) (Ma ck et al.1991). Mack (1992) evaluated the effect of granular in secticides on secondary pests and predators Sunrunner peanuts. No consistent effect was reported in secondary pests like Helicoverpa zea (Boddie) (Lepidopter a: Noctuidae) and Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctui dae), but population of predato rs declined after application 37

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of granular insecticides. Chapin and Thomas (1998) tried an alternate method of application of chlorpyrifos 15G which was considered to be time consuming and costly. They used chlorpyriphos 4E at 1.13 kg A I/ha as flood treatment which provides 90% control as compared to 94% in case of chlorp yrifos 15G at 2.26 kg AI/ha. This shows that 50% pesticide can be saved in flood treatm ent with almost same level of control. Chlorpyriphos had also the fungicidal activity against southern stem rot. Cunningham et al. (1959) reported the control of lesser co rnstalk borer with spray applications timed with the appearance of the moths of each generation. Effective results were obtained with DDT at 1.71 kg/ha and endrin at 0.47 kg/ha. Reynolds et al. (1959) reported that endrin, aldrin, heptachlor, and dieldrin were more effective as compared to thiodan for lesser cornstalk borer in sorghum. As sowi ng is followed by irrigation which reduced the strength of insecticides, applic ation of chemicals at the time of plant emergence was preferred over application at planting time. Corn In corn, carbofuran at 170.8g/1000 m row reduced the damage to 0% in notillage plots. Carbofuran also significant ly reduced damage in conventional tillage plots, but the infestation was still more than in untreated no-tillage plots (All and Gallaher 1977). Carbofuran at a lower rate (0.11 kg AI/1000 m row) was effective only if applied in seed furrows during planting in field co rn. In banded application at the time of planting, chlorpyriphos and fonofos at 0.22 kg AI/1000 m row were most effective in lesser cornstalk borer control (All et al. 1979) Calvo (1966) reported significant control of lesser cornstalk borer with applications of emulsion forms of Bayer 25141, G.C. 6506, diazinon, endrin, dimethoate, azinphosethy l, heptachlor, disulfoton, and bidrin; trichlorfon and Bayer 39007 as wettable pow ders and phorate as granules. These 38

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insecticides applied at the ra te of 1.13 kg AI/ha after fi rst signs of infestation appeared and directed towards the base of the plants. Endrin and diazinon were found to be the best in both light and heavy soils while Baye r 25141 was effective only in heavy soil. Sorghum In sweet sorghum, Henderson et al. (1973) reported Aldrin (10% G) at 2.27 kg AI/ha, carbofuran (10% G) at 4.54 kg AI/ ha and diazinon (14% G) at 1.14 kg AI/ha as effective insecticides in reducing lesser cornstalk borer damage. Gardener and All (1982) reported that fonofos and diazinon at moderatel y high rates (2.24 kg AI/ha) were the most consistent in controlling lesser corn stalk borer while carbofuran was variable in its activity in grain sorghum. Carbofuran reduced the damage significantly at lower rate (0.84 kg AI/ha) but was not as effectiv e at a higher rate (2.24 kg AI/ha). Cowpeas and Southern Peas On cowpeas, Wilson and Kelsheimer (1955) and Kelsheimer (1955) reported chlordane as an effective control measure when applied as a 5% dust at a rate of 28.35 kg/ha or as a spray applied at the rate of 1.7 to 2.27 kg/ha on cowpeas. Dupree (1964) reported aldrin, BHC, DDT, heptachlor and toxa phene in the form of granules, dusts and liquids to be the most effective insecticides against lesser cornstalk borer damage in southern peas. Sugarcane Bennett (1962) reported the high volume applic ation of endrin at the time of adult abundance in the field, resulted in satisfactory control of lesser cornstalk borer in Florida sugarcane. GY-81 (sodium tetrathiocar bonate) applied at 1600 ppm through drip irrigation system was report ed to be the only soil insectic ide which was consistently effective in reducing damage (Chang and Ota 1989). 39

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Many of the successful materials are no longer labeled for use on these or any other crops. Most recently, the United States Environmental Protection Agency revoked tolerances for carbofuran which was labeled fo r multiple insect control in sugarcane, effectively removing the last of the effective products for controlling lesser cornstalk borer larvae protected within plants (EPA 2009) Biological Control Due to excellent protection in the silken tunnels and sugarcane habitat, there were very less number of parasitoids and low parasitoidism. Also, with pre-havest burning of sugarcane, predator population destroyed and in rebuilding stage at the time of high borer population. Three species of larval parasites including Stomatomyia floridensis Townsend (Diptera: Tachinidae), Orgilus sp. ( Hymenoptera: Braconidae) and Pristomerus pacificus melleus Cushman (Hymenoptera: Ichneumonidae) caused 34.8% of parasitization of lesser corn stalk borer on soybean and southern peas in Georgia. S. floridensis was dominant followed by Orgilus sp. and P. pacificus melleus (Leuck and Dupree 1965). In Jamaica, Falloon (1974) recor ded 1.26% parasitoidism in February to 10.02% in July on sugarcane. Tachinids found to be most successful of the parasitoids followed by O. elasmopalpi C. elasmopalpi and the ichneumonid. In Florida, on corn, Knutson (1976) reported that the lesser cornstalk borer in its semisubterranean habit did not protect itself from parasites having long ovipositor capable of penetrating soil surface and silk tubes. In la rval parasites recorded from various crops (corn, peanuts, soybean and grain sorghum) in northern Florida, 98. 6% of all larval parasitism was done by braconid, Orgilus elasmopalpi Meusebeck, the ichneumonid Pristomerus spinator (F.) and the braconid, Chelonus elasmopalpi McComb (Funderburk et al 1984). Schauff (1989) reported a new parasite Horismenus elineatus 40

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Schauff (Eulophidae: Entedoninae ) from the specimens collect ed from corn in Texas. This is a gregarious endoparasit e of last three instars of lessser cornstalk borer. In predators, Heteropoda venatoria L. (Araneae: Sparassidae) was reported as voracious feeders of lesser cornstalk borer on s ugarcane in Jamaica (Falloon 1974). Sampling As lesser cornstalk borer is difficult to control after the plants show the symptoms of its attack and also signific ant damage done by that time. So prevention or control at early stage of its infestation known th rough sampling is beneficial. Pitfall and pheromone traps have been used to detect E. lignosellus activity. Pitfall traps were reported to be less time consum ing than manual sampling, particularly in wet soil (Jones and Bass 1979). Larger larvae were more a ccurately sampled than smaller ones by using pitfall traps. Payne and Smith (1975) were the first to report the occurrence of a female produced sex pheromone in the lesser cornstalk borer. They showed that pieplate-type sticky traps baited with lesser co rnstalk borer virgin females in the field captured lesser cornstalk borer males and t hat a diethyl ether extract of female abdomen was electrophysiologically and behaviorally excitatory to males. Lynch et al. (1984) reported 10 compounds fr om heptane extracts of lesser cornstalk borer female ovipositors. They tried different combinat ions of these compounds and finally came up with mixture of only four compounds, includi ng 91.6 g of (Z)-11-HAD, 11.2 g of (Z)-9TDOH, 46.4 g of (Z)-9-TDA and 86.8 g of (Z )-7-TDA. A mixture of these compounds applied to rubber septa retained activity for 30 d in a field. They also showed that a 92 cm height of trap installed in peanuts at reproductive st age gave the maximum capture of males as compared to other heights and ot her stages of the peanuts. Funderburk et al. (1985) compared the pherom one-trap captures of lesser cornstalk borer with the 41

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absolute numbers of adults in grain sorghum, soybean, peanut and corn. The relationship between trap captured and flushed adults (actual number) found to be statistically similar. They conclud ed that the pheromone trap captures can be considered as an important population monitoring tool fo r lesser cornstalk borer. Funderburk et al. (1987) used pheromone traps to study the seasonal abundance of lesser cornstalk borer in soybean, peanut, corn sorghum and wheat in northern Florida. Trap captures varied with crop and date of planting in same cr op. Results revealed that adults were present in abundance in peanut and sorghum in both vegetative and reproductive stages. In soybean, adult abun dance was only in vegetative and early reproductive stages while in wheat it was onl y in early seedling stages. Only few adults were captured in corn field. Mack and Backman (1988) compar ed the pheromone trap catches of adults with flush counts in peanut field and reported that they were not similar. They concluded that pheromone tr aps did not accurately determine the moths when in large number. Pheromone traps we re found to be good source of alert for growers against presence of lesser cornstalk borer. Research Goals Sugarcane, Saccharum officinarum L. is an important crop grown in Everglades Agricultural Area around Lake Okeechobee in Flor ida. There are several factors that can result in decreased sugarcane yield, including insect damage. Sugarcane as an agro-ecosystem is inhabited by many insect species in both above ground (aerial) and below ground (subterranean) habitats (Nuessly 2006) Lesser cornstalk borer is one of the important below ground pest of sugarcane. Detailed studies of this pest have been conducted on crops such as peanuts and corn, but only a few studies on sugarcane have been published. Carbonell (1978) 42

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studied the biological paramet ers of lesser cornstalk bor er on sugarcane under natural climatic conditions. Due to uncontrolled temper ature conditions, it was difficult to model the development of lesser cornstalk borer based on temperature and to predict its population. Therefore, det ailed studies on developmen t of immature stages and reproductive biology need to be conducted on s ugarcane at constant temperatures to understand variations in popul ation with temperature. The quantitative information on the effects of lesser cornstalk borer feeding on sugarcane growth and yield was al so not available. This information on variety specific sugarcane response to E. lignosellus damage would be useful for the industry in their variety selection program. This informati on is also important for developing damage thresholds for use in integrated management of this pest in the numerous susceptible grass and vegetable crops grown throughout the southeastern United States. Also the subterranean feeding habit and exce llent protection afforded by silken tunnels makes control of lesser cornstalk borer difficult. Chemical control strategies attempted by many researchers has been ine ffective in lesser cornstalk borer control (Kelsheimer 1955, Arthur and Arant 1956, Reyn old et al. 1959, Harding 1960, Falloon 1974, Chalfant 1975, Chapin and Thomas 1998). Biological control was also found to be inefficient to control lesser cornstalk bor er in sugarcane (Falloon 1974). Several cultural strategies provided effective E. lignosellus control in different crops (Ingram et al. 1951, Schaaf 1974, Smith and Ota 2002, Cheshire and All 1979). T herefore, cultural practices against lesser cornstalk bor er need to be evaluated in sugarcane. Due to the importance of lesser cornstal k borer as a pest in Florida sugarcane, lack of knowledge in biology of this pest, effect of its feeding on sugarcane yield, and 43

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having a limited number of available contro l strategies, studies are needed on various aspects related to lesser cornstalk borer that may lead to improved control. Research objectives proposed to better understand the in sect/plant interactions and to develop effective control strategi es were the following: 1. To study temperature-dependent immature development of lesser cornstalk borer on sugarcane under labor atory conditions. 2. To study reproductive biology and esti mation of life table parameters of lesser cornstalk borer on sugarcane. 3. To determine the effects of lesser co rnstalk borer feeding on sugarcane growth and yield. 4. To evaluate cultural control practi ces against lesser cornstalk borer damage to sugarcane. 44

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Table 1-1. Known host plants of Elasmopalpus lignosellus (Zeller) Common name Scientific name Family References Garden stock Matthiola sp. Brassicaceae Reynolds et al (1959) Cultivated radish Raphanus sativus L. Brassicaceae Carbonell (1977) Black tupelo Nyssa sylvatica Marsh. Cornaceae Dixon (1982) Flowering dogwood Cornus florida L. Cornaceae Dixon (1982) Turnips Brassica napus L. Crucifereae Lugi nbill and Ainslei (1917), Carbonell (1977) Cabbage Brassica oleracea L. var. capitata L. Crucifereae Guagliumi (1966) Cantaloupe Cucumis melo L. Cucurbitaceae Sanchez (1960) Arizona cypress Cupressus arizonica Greeni Cupressaceae Reynolds et al (1959), Dixon (1982) Southern red Cedar Juniperus silicicola Bailey Cupressaceae Dixon (1982) Chufa Cyperus esculentus L. var. sativus Boeckl. Cyperaceae Luginbill and Ainslei (1917) Nutsedge Cyperus rotundus L Cyperaceae Carbonell (1977), Smith and Ota (2002) Peanuts Arachis hypogaea L. Fabaceae Cunningham et al. (1959), Harding (1960), Dupree (1964), Carbonell (1977) 45

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Table 1-1 Continued Common name Scientific name Family References Soybeans Glycine max. (L.) Merr. Fabaceae Leuck (1966) Beans Phaseolus sp. Fabaceae Isley and Miner (1944), Bissell (1945), Kelsheimer (1955), Reynolds et al. (1959) Butter beans Phaseolus lunatus L. Fabaceae Guagliumi (1966), Carbonell (1977) Mung beans Phaseolus vulgaris L. Fabaceae Carbonell (1977) Black locust Robinia pseudoacacia L. Fabaceae Dixon (1982) Chinese beans Soja hispida Moench. Fabacae Carbonell (1977) Crimson clover Trifolium incarnatum L. var. elatius Gibelli and Belli Fabaceae Bissell (1945) Horse beans Vicia faba L. Fabaceae Carbonell (1977) Hairy cowpeas Vigna luteola (Jacq.) Benth. Fabaceae Carbonell (1977) Cowpeas Vigna sinensis (L.) Endl. Fabaceae Isley and Miner (1944), Heinrich (1956), Dupree (1964), Black-eyed peas Vigna sinensis (L.) Endl. Fabaceae Sanchez (1960) Gladiolus Gladiolus sp. Iridaceae Bissell (1945) Flax Linum usitatissimum L. Linaceae Heinrich (1956) Cotton Hibiscus gossipium L. Malvaceae Reynolds et al (1959) 46

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Table 1-1 continued Common name Scientific name Family References Sand pine Pinus clausa Pinaceae Dixon (1982) Slash pine Pinus elliottii Pinaceae Dixon (1982) Loblolly pine Pinus taeda L. Pinaceae Dixon (1982) Burnut grass Aegilops sp. Poaceae King et al (1961) Foxtail Alopecurus pratensis L. Poaceae Isley and Miner (1944) Oats Avena sativa L. Poaceae Sanchez (1960), Carbonell (1977) Rhodes grass Chloris gayana Kunth Poaceae Calvo (1966) Bermuda grass Cynodon dactylon (L.) pers. Poaceae Reynolds et al (1959), Dupree (1964) Nut grass Cyperus esculentus L. Poaceae Bissell (1945), Reynolds et al (1959) Water grass Cyperus sp. Poaceae Reynolds et al (1959) Crab grass Digitaria sanquinalis (L.) Scop. Poaceae Isley and Miner (1944), Reynolds et al (1959), Sanchez (1960), Dupree (1964) Barnyard grass Echinochloa crusgalli (L.) Beauv. Poaceae Isley and Miner (1944) Gulf grass Echinochloa cruspavonis (Kunth) Poaceae Carbonell (1977) Wire grass Elausine indica (L.) Gaertn. Poaceae Carbonell (1977) Mexican teosinte Euchlaena mexicana Schrad. Poaceae Guagliumi (1966) Barley Hordeum vulgare L. Poaceae Reynolds et al.(1959) Rice Oryza sativa L. Poaceae Guagliumi (1966) 47

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Table 1-1 continued Common name Scientific name Family References Johnson grass Sorghum halepense (L.) pers. Poaceae Dupree (1964), Carbonell (1977) Milo maize Sorghum subglabrescens (Steud.)A.F.Hill Poaceae Luginbill and Ainslei (1917) Sudan grass Sorghum Sudanese (Piper) Stapf Poaceae Guagliumi (1966) Kafir corn Sorghum vulgare Pers. Var. caffrorum (Retz.) Hubbard and Rehder Poaceae Guagliumi (1966), Hegari Sorghum vulgare Pers. Poaceae Sanchez (1960), Guagliumi (1966) Broom corn Sorghum vulgare Pers. Var. technicium (Koern.) Fiori and Paoletti Poaceae Guagliumi (1966), Wheat Triticum aestivum L. Poaceae Luginbill and Ainslei (1917), Carbonell (1977) Corn Zea mays L. Poaceae Luginbill and Ainslei (1917), Isley and Miner (1944), Sanchez 1960), Carbonell (1977) Common buckwheat Fagopyrum esculentum Moench Polygonaceae Guagliumi (1966) Strawberries Fragaria virginiana Duch. Rosaceae Stahl (1930), Isley and Miner (1944), Kelsheimer (1955). Pimento Capsicum frutescens L. Solanaceae Bissell (1945), Wilson and Kelsheimer (1955) 48

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CHAPTER 2 TEMPERATURE-DEPENDENT DEVELOPMENT OF LESSER CORNSTALK BORER, ELASMOPALPUS LIGNOSELLUS (LEPIDOPTERA: PYRALIDAE) ON SUGARCANE UNDER LABORATORY CONDITIONS Introduction The lesser cornstalk borer is a polyphagous pest attacking many crops including corn (Zea mays L.), peanuts ( Arachis hypogaea L.), field peas ( Pisum sativum L.), beans (Phaseolus vulgaris L.), soybeans [ Glycine max (L.) Merr.], wheat ( Triticum spp L.), barley ( Hordeum vulgare L.), oats ( Avena sativa L.), rice ( Oryza sativa L.), cotton ( Gossypium spp. L.), cowpeas [Vigna unguiculata (L.) Walp.], nurseries of forest trees, and sugarcane ( Saccharum officinarum L.) (Luginbill and Ainslie 1917, Heinrich 1956, Harding 1960, Leuck 1966, Fall oon 1974, and Dixon 1982). It is widely distributed in tropical through temperate regions of the Ne w World, including Hawaii and the southern half of the United States from California to the Carolinas, north on the east coast to Massachusetts, and south through Central and S outh America to Argentina, Chile, and Peru (Heinrich 1956, Genung and Green 1965, Chang and Ota 1987). Lesser cornstalk borer is a semi-subte rranean pest that attacks sugarcane at or below the soil level. Larvae bore into sugarcane stems below the soil surface and produce a silken tunnel at the entrance hole out ward into the soil from which they attack the plants, as well as rest, molt and pupat e (Schaaf 1974). Dead heart symptoms are produced when larvae reach the center of the shoot and damage or sever the youngest leaves or apical meristem. Non-lethal dam age is caused when larvae only chew a few millimeters into the shoot evidenced by several symmetrical rows of holes revealed as the leaves emerge from the whorl. Larval feeding damage reduces sugarcane photosynthesis, plant vigor, number of millabl e stalks, and sugar yield (Carbonell 1977). 49

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The first record of lesser cornstalk borer as an economic pest was in 1878 in Georgia and South Carolina on corn (Riley 1 882). Outbreaks of lesser cornstalk borer in sugarcane were reported by Plank (1928) in Cuba, Wolcott (1948) in Puerto Rico, and Genung and Green (1965) in Florida. It is a potentially serious pest of sugarcane in Jamaica (Bennett 1962) where it was first reported in 1959. Chang and Ota (1987) reported the lesser cornstalk bor er for the first time on Kaua i (Hawaii) in 1986 causing 100% dead hearts in ratooned sugarcane fields. Biological parameters of the lesser co rnstalk borer life cycle were studied on cowpea in South Carolina and Florida (Lugi nbill and Ainslei 1917), peanut in Georgia (Sanchez 1960) and Texas (King et al. 1961), and southern pea (Dupree 1965) and soybean (Leuck 1966) in Georgia. Published studies on E. lignosellus development on sugarcane were conducted unde r uncontrolled, natural climatic conditions (Carbonell 1978). Therefore, it is not possibl e to determine the relationship between developmental rates and tem perature. Underst anding the physiological relationship between temperature and develop ment is important for t he prediction of population outbreaks and timely management of pests on crops (Jervis and Copland 1996). The objective of this study was to determi ne the relationships between temperature and development and survivorship of the immature stages of E. lignosellus on sugarcane under controlled temperature conditions. Materials and Methods Temperature-dependent development of immature stages of lesser cornstalk borer was studied under laboratory conditions. Inse cts from a laboratory colony were reared on young sugarcane shoots to study development al rates, temperature thresholds and survivorship. 50

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Insect Colony Maintenance The laboratory colony was started using larvae, pupae and adult E. lignosellus (Fig. 2-1) collected on October through December, 2006 from sugarcane fields at Belle Glade and Moore Haven, Florida. Adults co llected from fields were transferred to oviposition cages (17.5 17. 5 17.5 cm) covered with 30 mesh screen and provided with 10% honey solution for feeding. T ubular synthetic stockinette (Independent Medical Co-Op, Inc., Ormond B each, Florida) was used to li ne the oviposition cages for egg deposition. Stockinette with eggs was transferred to ziploc bags (S. C. Johnson & Son, Inc., Racine, WI) and maintained for la rval emergence in the same environmental conditions as the adults. Newly emerged la rvae were transferred to a wheat germ and soy flour base artificial diet (General purpose diet for Lepidoptera, Bio-Serv, Frenchtown, NJ) covered with a thin layer of fine vermiculite (no. 4, Thermo-o-rock, East, Inc., New Eagle, PA) in 32-cell diet trays (43.75 20.62 2.5 cm, Bio-Serv, Frenchtown, NJ). The artificial diet consisted of 144.0 g/liter dry mix and 19 g/liter agar. Four newly emerged larvae were released in each diet cell and kept under the same environmental conditions as the adults. Larv ae were allowed to complete development within the trays. Adults that emerged from pupae within the diet were collected and transferred to oviposition cages. The colony was maintained in a temperature control room at 27 C, 65-70% RH, and 14:10 (L:D) h photoperiod. Production of Sugarcane Plants Mature stalks of sugarcane variety CP 78-1628 were harvested in November, 2006 and 2007 to obtain viable buds for use in producing shoots for examining larval development. Stalks were cut into 10 cm-l ong seed pieces (i.e., single eye sets) and planted in plastic trays (50 36 9.5 cm) f illed with potting mix to germinate the buds 51

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and produce shoots. Plants were maintained in a greenhouse, fertilized and irrigated as needed. To study larval development on su garcane, young sugarcane shoots (4-5 leaf stage) were uprooted from tr ays in the greenhouse and separat ed from the billets by cutting around the base of the eye, so that a small part of the seed piece remained attached with the shoots and roots. The bases of the shoots were wrapped with moistened paper towel to promote continued r ooting and to maintain seedling viability. Laboratory Temperatur e Developmental Studies The effect of temperature on lesser cornstalk borer development was examined at nine temperatures [13, 15, 18, 21, 24, 27, 30, 33 and 36 C ( 0.05 C)], at 14:10 (L:D) h and 65-70% RH in temperature control cham bers. Relative humidity was maintained by placing plastic containers filled with wa ter in these chambers. Freshly deposited eggs (< 12 h old) from the laborat ory colony were used to determine the development of egg stage. Eight batches of 50 eggs each we re placed in separate Petri plates and observed for the emergence of larvae. The egg developmental period was reported as the time required for emergence > 50% larvae in each batch (Leuck 1966). To observe larval development, sugarcane shoots produced as above were placed horizontally in plastic containers (30 15 10 cm) fitted with 30 mesh screen at the top for aeration (Fig. 2-2). There was a thin layer of vermiculite covering the base of each shoot, five shoots per container. Fifteen newly emerged larvae were co llected from the laboratory colony and placed in each container. Eight c ontainers per replicate were tested at each temperature [13, 15, 18, 21, 24, 27, 30, 33 and 36 C ( 0.05 C)]. The experiment was repeated three times at each temperature. The experimental des ign was a randomized complete block replicated through time. Ol d shoots were replaced with new ones as 52

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required (i.e., when old ones started desiccati ng) to provide live shoots throughout larval development. The number of days from larval emergenc e to pre-pupal formation was considered as total larval duration. To study the duration of each instar, larvae needed to be closely observed for exuviae and head capsules which was not possible in the large arenas of the plastic boxes. To solve th is problem, the progre ssion of larvae through individual instars was closely observed in gl ass test tubes set up at the same time and placed in the same temperature control c abinets along with the 15-la rvae containers. A single neonate larva was placed on a piece of young sugarcane shoot (4 cm long) in each test tube (15 cm long x 2 cm diam.). Stem pieces were changed daily, and the vials observed for exuviae and head capsules twice daily. Four groups of 40 larvae each were tested at each temperature, and this experiment was replicated three times at each temperature. The chang e in larval instar was determined by presence of newly cast exuviae. Fully grown larvae stop feeding before pupation and become dirty creamy white in color. This pre-pupal period wa s measured as the time from cessation of feeding up to the beginni ng of the pupal stage. Pupae were collected from each plastic container and placed in plastic Petri dishes with 90 mm diameter and 15 mm height (total eight Petri dishes) lined with moistened paper towel to determine the length of the pupal period. The time taken from the first day of the pupal stage up to adult em ergence was defined as the pupal period. Cohorts of immature E. lignosellus were followed from egg depostition through adult emergence to measure survivorship. Percentage survival was calculated using 53

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the formula Nc x 100 / Ni, where Nc was the number of indi viduals that completed development, and Ni was the total number of indivi duals that started each stage. Developmental Rate and Mathematical Models The results of the developm ent experiments were used to model developmental rate (d-1, reciprocal of developmental time in days) and to estimate developmental thresholds. In all immature stages (eggs, larvae, pre-pupae, and pupae), developmental rate was regressed agains t temperature using linear and non-linear models (SAS Institute 2008). One linear and six non-linear models (Table 2-1) that have been commonly used to describe temper ature-dependent developm ent of insects such as Ostrinia nubilalis (Hubner) (Lepidoptera: Pyrali dae) (Got et al. 1996), Plutella xylostella L. (Lepidoptera: Plutellidae) (Golizadeh et al. 2007), Cydia pomonella L. (Lepidoptera: Tortricidae) (Aghdam et al. 2009), and Halyomorpha halys (Stal) (Hemiptera: Pentatomidae) (Nielsen et al. 2008), were evaluated to describe the relationship between temperature and development al rate of lesser cornstalk borer. The parameters of interest were T0, Tm, Topt, and K. The lower developmental threshold is the temperature at or below which no measurable development is detected (Howell and Neven 2000). It can be estimated from a linear model as the intercept of the development line with the temperature axis. Some non-linear models (Briere-1, Briere2, and Taylor model) can also estimate the lo wer developmental threshold directly from the model equation. The upper developmental threshold is the temperature at or above which development does not occur (Kontodima s et al. 2004). It is better estimated through the non-linear models (Briere-1, Briere-2, Logan-6, and Lactin model), because a linear model is asymptotic to the tem perature axis at high temperatures. The 54

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temperature at which the developm ental rate is greatest is Topt. In Briere-1 and Briere-2 models, it was calculat ed by using the equation Topt. = (2mTm + (m + 1)T0) + 4m2Tm 2+ (m + 1)2T0 2 4m2Tm T0 / 4m +2 where m is an empirical constant which equals two for the Briere-1 model (Briere and Pracos 1998). In Taylors model, Topt. was estimated directly from the mathematical equation [Rm exp(-.5((T Topt.)/T0)2], where Rm is the maximum developmental rate. In Logan-6 and Lactin models, Topt can be estimated as the parameter value for which their first derivatives equals zero. The t hermal constant determines the amount of thermal units (degree days) required by an immature stage to complete its development. It can be estimated directly from the linear equation as the value of K (thermal constant) (Aghdam et al. 2009). The developmental rate of lesser cornst alk borer was positively correlated with temperature until the upper lim it of 33 C in all developmental stages and total development. In the linear model, the developmental rate at 36 C was omitted to produce linearity in the data. The omission was important to ensure a better fit of the linear model and to calculate the correct values of the T0 and K (DeClerq and Degheele 1992). Sigma Plot (Systat Software, Inc., S an Jose, CA) was used to plot regressions of the non-linear models. Performance of a mathematical model is commonly evaluated with the coefficient of determination (r2), which indicates better fits with higher values, and the residual sum of squares (RSS), which indica tes better fits with lower val ues (Aghdam et al. 2009). In this study we used an additiona l parameter, Akaike information criterion (AIC), to further estimate the goodness-of-fit for all tested mathematical model s. The AIC considers the 55

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number of parameter s in the model, and we sought t he model with the lowest AIC = n ln(SSE/n) + 2p, where n is t he number of treatm ents, p is the number of parameters in the model, and SSE is the su m of the squared error. Data Analysis PROC MIXED (SAS institute 2008) was us ed to analyze the data due to potential covariance structure associated with taking r epeated measures on cohorts through time at each temperature. Temperature, cohorts (plastic containers and Petri dishes), generations (replications thr ough time), and their interactions were modeled in this experiment. Generations were used as the repeated variable and the cohorts were nested under the temperature in the repeated measures stat ement. Several covariance structures were fitted to the data. The unstructured covariance type fit well and was used for the analysis (Littell et al. 1998). Percentage data were arcsin transformed before analysis and retransformed for presentation purposes. The Tukeys HSD test (SAS Institute 2008) was used for means separation with = 0.05. Results Laboratory Temperatur e Developmental Studies All immature stages of lesser cornstalk borer completed their development at temperatures between 13 C and 36 C. De velopmental time decreased with increase in temperature between 13 C and 33 C, and then increased at 36 C in all immature stages and for total development (Table 2-2). Cohorts (P > 0.93) and generations ( P > 0.88) did not provide significant sources of variation in the models for the developm ent of eggs, larvae, pr e-pupae, pupae or total development of lesser cornstalk borer. None of the modeled interactions ( P > 0.98) were significant sources of variation in the model. Due to the insignificant effects of 56

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cohorts and generations on developmental times, the data for each temperature were pooled across time and containers and analyzed together to determine the effect of temperature. Temperature had a significant effect on development in all immature stages (Table 2-2). Mean egg developmental time ( SEM) ranged from 1.8 0.1 d at 33 C to 17.5 0.1 d at 13 C (Table 2-2). The mean develop mental time for larvae ranged from 15.5 0.1 d at 33 C to 65.7 0.4 d at 13 C. Larvae completed six instars before pupating. Temperature had a significant e ffect on the development of a ll six instars (Table 2-3). Developmental time was shortest in the first instar and longest in the sixth instar at all temperature treatments (Tabl e 2-3). Mean pre-pupal deve lopment ranged from 1.3 0.1 d at 33 C to 10.5 0.1 d at 13 C. Pupal developm ent ranged from a mean of 5.9 0.1 d at 33 C to 29.5 0.2 d at 13 C (Table 2-2). Mean total development ranged from 22.8 0.3 d at 33 C to 120.7 2.8 d at 13 C. Survivorship of immature stages at each temperature treatment is presented in Table 2-4. Survivorship rose with increas ing temperature for all immature stages, peaking at 27 C, and then decreasing with fu rther increases in temperature. At extreme temperatures (13 C and 36 C), percentage survival was quite low with < 50% of eggs, larvae, pupae and pre-pupae surviving at 13 C. Egg and larval survival dropped below 50% at 36 C. Cohorts ( P > 0.72) and generations ( P > 0.73) were not a significant source of variation in the model s for the survival of eggs, larvae, pre-pupae, and pupae of lesser cornstalk borer. N one of the modeled interactions (P > 0.96) were significant sources of variati on in the model. Due to the in significant effects of cohorts and generations on survivorship, the data for each temperature were pooled across 57

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time and containers and analyzed together to determine the effect of temperature. Temperature had a significant effect on t he survival of all immature stages of E. lignosellus (Table 2-4). Model Evaluation The fitted coefficients T0 and K, and model eval uation parameters (r2, RSS, and AIC) estimated by the linear regression equation are presented in Table 2-5. The linear model (without the data from 36 C) provided a good fit to the data in all immature stages with high r2 (> 0.96) and low RSS (< 0.027) and AIC (< -60.56) values. The linear regression model estimated that le sser cornstalk borer required 543.5 degree days (DD) to complete development fr om egg deposition to adult emergence on sugarcane with a lower developm ental threshold of 9.5 C. The upper developmental threshold was not estimated by the linear model, because the fitted line did not intersect the x-axis at higher temperature. The estimates of the fitted coefficient s, measurable paramet ers and evaluation indices for the non-linear models are present ed in Table 2-6. Among all non-linear models, the Briere-1 model provided the best fit to the data with high r2 values, and low RSS and AIC values for each immature devel opmental stage. The relationship between developmental rate (d-1) of immature stages and temperature (C) described by Briere-1 equation is presented in figures 2-3 to 2-7. The Briere-1 model provided estimates closer to actual observations for para meters of biological significance (T0, Topt and Tm) for all immature stages and for the total im mature development than the other non-linear models tested. Furthermore, the Lactin, Logan-6, and the Taylor models recorded low r2 values and high RSS and AIC values and did not provide good fits to the data. The Taylor model estimated Topt, but due to the absence of Tm in this equation, direct 58

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estimation of Tm was not possible. In poly nomial models, first degree (r2 = 0.435), second degree (r2 = 0.574), and third degree (r2 = 0.612) polynomials had poor fit to the data. The fourth degree polynomial model was a good fit (r2 = 0.925) to the data, but due to the greatest number (four ) of fitted paramet ers, AIC value increased, and it decreased the fitness of this model to the dat a. The Briere-2 model was also a good fit (r2 = 0.865) for the data, but the estimated lower developmental threshold values for larval (-3.5 C), pupal (0.0 C), and total development (1.2 C) were much lower than the observed and estimated values produced by all other tested developmental models. Discussion Laboratory Temperatur e Developmental Studies Results of this study indicated that developmental time and temperature were closely related in all immature stages of lesser cornstalk borer. Developmental time decreased with increased te mperature and increased abov e the thermal optimum. Previous studies on the life cycle of lesse r cornstalk borer were conducted under uncontrolled temperature conditions on most crops; therefore, it is difficult to directly compare the results. T he reported egg developmental times of 6-8 d on cowpeas (Luginbill and Ainslei 1917) and 2.4 and 4 d on soybean (Dupree 1965 and Leuck 1966, respectively) all fall within the range of 1.8 d at 33 C to 17.5 d at 13 C determined for E. lignosellus on sugarcane. Dupree (1965) reported larval developmental times of 4.2, 2.9, 1.4, 3.1, 2.9, and 8.8 d, while Leuck (1966) reported 2.6, 1.8, 1.8, 2.0, 2.8, and 8.6 d for first through sixth instar s on soybean, respectively. In both studies, development of the first instar was slower for through fifth instars. In co ntrast to these reports, first instar larvae on sugarcane completed development rapidly at all temperatures. Sixth instar larvae required more time (approximat ely three-fold) to co mplete development 59

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than other instars on both soybean and sugarc ane. Mean larval developmental time was reported as 15.6 to 16.9 d on cowpeas (Luginbill and Ainslei 1917), and 30.3 d on sugarcane (Carbonell 1978). These were within t he range of our results for mean larval developmental time ranging from 13.8 d at 33 C to 63.2 d at 13 C on sugarcane. Prepupal development could not be compared with pr evious studies because other studies did not separate this time segm ent from the overall larval developmental period. Most of the pupal period developmental rates reported by others fell within the range determined in the present study on sugarcane (i .e., 5.9 d at 33 C to 29.5 d at 13 C). Pupal period was reported to be 7-21 d (Luginbill and Ainslei 1917), 7-10 d (Dupree 1965), 3-24 d (Leuck 1966), and 10.9 d (Carb onell 1978) in studies on cowpeas, soybeans, soybeans, and sugarcane respectively. Model Evaluation One of the objectives of this study was to select a mathematical model that could best describe the relationship between temperature and lesser cornstalk borer developmental rate on sugarcane. Our re sults showed that developmental rate increased fairly linearly with an increase in temperature, but decreased at high temperature (36 C) breaking the linear trend. Similar trends were reported for other insects such as Nephus includens (Kirsch) (Coleoptera: Cocci nellidae) (Kontodimas et al. 2004) and P. xylostella L. (Golizadeh et al. 2007). Linear models were used to determine the lower developmental threshold and thermal constant or degree days (DD) in many temperature-dependent developmental studies (Geier and Briese 1978, Rock and Shaffer 1983, Howell and Neven 2000). However, due to the non-linear relationship between developmental rate and temperature at 36 C for E. lignosellus on sugarcane, the linear equation could only model developmental rate within the 60

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temperature range of 13-33 C. If we use all the available data over the entire range of tested temperatures, then the slope of the linear model becomes depressed and results in inaccurate simulations of developmental rates and thresholds at both ends of the temperature range (How ell and Neven 2000). Insect developmental model perform ance has varied depending on species studied. Good model fits to insect development have been reported for the Logan model on Helicoverpa zea (Boddie) (Lepidoptera: Noctui dae) (Coop et al. 1993), the Lactin-2 model on Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) (Fantinou et al. 2003), the Briere-2 model on P. xylostella L. (Golizadeh et al. 2007), and both Briere-1 and Briere-2 models on C. pomonella L. (Aghdam et al. 2 009). In another pyralid, European corn borer, O. nubilalis (Lepidoptera: Pyralid ae), the Logan-6 model was reported to be the best fit to the data and T0, Topt. and Tm were estimated as 10, 34, and 40 C, respectively (Got et al. 1996). In our study, the Briere-1 model provided the best fit, and the estimated T0, Topt and Tm for total development of immature stages were 9.35, 31.39, and 37.90 C, respectively, which are similar to the estimation for European corn borer. Differing model performanc e reported in the lit erature is possibly caused by differences in thermal adaptation of different insects or by differences in the host crop. This study determined the temperatur e-dependent development of lesser cornstalk borer on sugarcane under a series of constant temperatures. The developmental rate model derived from this study can be used to estimate the developmental time of this insect under natural conditions of temperat ures varying within an appropriate range for the purpose of developing an improved pest m anagement practice. Information on the 61

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life history, developmental thresholds, and t hermal requirements can be used to predict the developmental rates under varying te mperature conditions. These data are essential in an integrated system to opt imize lesser cornstalk borer control. 62

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Table 2-1. Developmental models and their mathematical equations tested to describe the relationship between temperatur e and development of lesser cornstalk borer on sugarcane. Model Equation References Linear K/ (T T0) Roy et al. (2002) Briere-1 aT(T T0) (sqrt(Tm T)) Briere et al.(1999) Briere-2 aT(T T0) ((Tm T) (1/d)) Briere et al.(1999) Logan-6 mx(exp( T) exp( Tm (Tm T)/ )) Logan et al. (1976) Lactin exp( T) exp( Tm ((Tm T)/ )) + Lactin et al.(1995) Taylor Rm exp(-.5((T Topt)/T0)2) Taylor (1981) Polynomial (fourth order) a(T)4 + b(T)3 + c(T)2 + d(T)+ e Lamb et al. (1984) K, thermal constant or degree da ys; T, rearing temperature; T0, lower temperature threshold; Tm, upper temperature threshold; Topt., optimum temperature; a, b, c, d, e, empirical constant; mx, growth rate at given base temperature; developmental rate at optimal temperature; number of degrees over the base temperature over which thermal inhibition becomes predominant; empirical constant which forces the curve to intercept the yaxis at a value below zero; Rm, is the maximum dev elopmental rate. 63

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Table 2-2. Mean ( SEM) developmental ti mes (d) by temperature for egg through pupal stages of lesser cornstalk borer on sugarcane under laboratory conditions. Developmental stages Temp (C) Eggs Larvae Pre-pupae Pupae Total development 13 17.5 0.2a 65.7 0.4a 10.5 0.2a 29.5 0.2a 120.7 2.8a 15 11.4 0.2b 51.0 0.4b 7.8 0.1b 23.4 0.2b 93.9 2.4b 18 6.8 0.1c 35.1 0.3c 3.6 0.1c 17.3 0.2c 69.9 2.0c 21 4.4 0.1d 27.4 0.3d 2.1 0.1e 11.8 0.2d 49.8 1.8d 24 2.8 0.1f 20.9 0.2e 1.8 0.1f 9.9 0.1f 39.7 1.3e 27 2.5 0.1g 17.3 0.2f 1.6 0.1g 7.8 0.1g 29.8 1.0g 30 2.2 0.1h 16.7 0.2g 1.4 0.1h 6.6 0.1h 26.1 0.7h 33 1.8 0.1i 15.5 0.2h 1.3 0.1i 5.9 0.1i 22.8 0.3i 36 3.3 0.1e 20.7 0.2e 2.2 0.1d 10.1 0.1e 37.2 0.9f F 26512.3 28661.3 10683.9 37693.9 69445.5 df 8, 897 8, 2099 8, 1834 8, 1722 8, 1542 P <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 F df and P values represent ANOVA of temperature treat ments within a developmental stage (PROC MIXED, SAS Institute 2008). Means within a column followed by the same letters are not significantly different (Tukey, P > 0.05); ANOVA (PROC GL M, SAS Institute 2008). 64

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Table 2-3. Mean ( SEM) developmental time (d) by temperature for lesser cornstalk borer larval instars on sugar cane under laboratory conditions. Larval instar Temp (C) I II III IV V VI 13 6.3 0.1a 7.2 0.1a 8.9 0.1a 10.2 0.1a 10.8 0.1a 19.8 0.3a 15 4.2 0.1b 5.8 0.1b 7.2 0.1b 8.3 0.1b 8.9 0.1b 16.9 0.1b 18 3.8 0.1c 4.9 0.1c 5.9 0.1c 6.1 0.1c 7.2 0.1c 14.3 0.1c 21 3.2 0.1d 3.4 0.1d 4.2 0.1d 4.9 0.1d 5.6 0.1d 10.2 0.1d 24 2.8 0.1e 2.9 0.1e 3.1 0.1f 3.4 0.1f 4.1 0.1f 8.9 0.1e 27 2.1 0.1g 2.4 0.1gf 2.5 0.1g 2.5 0.1g 2.7 0.1f 5.7 0.1g 30 2.0 0.1h 2.0 0.1g 2.3 0.1g 2.3 0.1h 2.2 0.1f 5.1 0.1h 33 1.7 0.1i 1.7 0.1h 2.0 0. 1g 2.1 0.1i 2.0 0.1g 4.3 0.1i 36 2.3 0.1f 2.4 0.1f 2.7 0. 1e 3.4 0.1e 3.6 0.1e 7.2 0.1f F 1901.7 2326.1 4929.5 6539.5 5645.8 21910.9 df 8, 379 8, 364 8, 339 8, 315 8, 301 8, 277 P <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 F df and P values represent ANOVA of temperat ure treatments withi n a developmental stage (PROC MIXED, SAS Institute 2008). Means within a column followed by the same le tters are not significantly different (Tukey, P > 0.05); ANOVA (PROC GLM, SAS Institute 2008). 65

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Table 2-4. Mean ( SEM) percentage survival by temperature of lesser cornstalk borer immature st ages under laboratory conditions. Developmental stages Temp (C) Eggs Larvae Pre-pupae Pupae 13 50.3 1.9f 39.9 1. 5g 45.5 1.6g 51.0 2.3 f 15 67.6 2.3e 55.5 2.1f 58.0 2.1f 65.4 3.0e 18 75.6 2.5d 58.0 2.4e 62.0 2.1e 74.9 3.2d 21 77.7 2.9c 70.4 2.7c 70.0 2.3d 81.8 3.8c 24 85.2 2.8b 71.7 2.9cb 86.8 2.6c 89.3 3.7b 27 92.7 3.2a 80.4 2.9a 92.1 3.2a 95.0 3.9a 30 91.2 3.4a 73.0 2.4b 90.2 3.2b 93.7 3.8a 33 79.1 2.4c 65.0 2.3d 88.8 .4b 75.0 2.9d 36 48.4 1.7f 46.2 1.8f 61.3 2.1ef 52.6 1.7 f F 601.15 435.47 611.44 429.54 df 8, 269 8, 269 8, 269 8, 269 P <0.0001 <0.0001 <0.0001 <0.0001 F df and P values represent ANOVA of temperature treat ments within a developmental stage (PROC MIXED, SAS Institute 2008). Means within a column followed by the same letters are not significantly different (Tukey, P > 0.05); ANOVA (PROC GL M, SAS Institute 2008). Table 2-5. Parameters from linear regre ssion of developmental rate and temperature for lesser cornstalk borer on s ugarcane under laboratory conditions. Developmental stage T0 K r2 RSS (-4) AIC Eggs 11.341 39.370 0.988 270.010 -78.171 Larvae 9.070 344.832 0.977 73.020 -114.270 Pre-pupae 9.881 27.931 0.967 157.000 -60.563 Pupae 8.902 142.453 0.994 1.031 -110.832 Total development 9.460 543.481 0.992 1.201 -132.331 1T0, lower developmental threshold; K, thermal constant; r2 coefficient of determination; RSS, residual sum of squar es; AIC, Akaike information criterion. 66

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Table 2-6. Fitted coeffici ents and evaluation indices for six non-linear developmental models of lesser cornstalk borer dev elopmental rate on sugarcane. Model Parameter Eggs Larvae Pre-pupae Pupae Total development a( 10-4) 3.3 3.0 50.0 9.0 2.0 T0 11.79 8.50 10.29 8.90 9.35 Tm 37.30 38.34 37.16 37.60 37.90 Topt 31.29 31.65 30.9 31.11 31.39 r2 0.953 0.922 0.979 0.942 0.942 RSS ( 10-4) 30.0 0.5 28.6 0.3 0.1 Briere-1 AIC -75.12 -115.89 75.59 -121.51 -132.16 a( 10-4) 5.6 0.6 5.7 1.4 38.0 T0 8.30 -3.50 9.20 0.07 1.20 Tm 36.00 36.00 36.60 36.00 36.00 Topt 29.76 28.47 30.36 28.80 28.92 d 5.90 24.88 2.58 9.59 10.29 r2 0.865 0.732 0.861 0.925 0.852 RSS ( 10-4) 30.0 0.5 28.5 0.3 0.1 Briere-2 AIC -73.12 -114.06 73.63 -119.86 -129.20 mx 0.010 0.005 0.086 0.011 0.003 Logan-6 0.08 0.09 0.07 0.09 0.09 Tm 36.05 37.42 36.03 37.37 37.53 Topt 32.82 33.12 32.79 31.59 33.19 0.15 2.30 0.05 2.67 2.85 r2 0.798 0.724 0.712 0.853 0.728 RSS ( 10-4) 146.0 1.9 60.2 1.04 0.1 AIC -57.29 -53.7 43.12 -66.7 -69.20 0.017 0.003 0.017 0.006 0.002 Tm 37.58 36.66 36.05 38.07 36.77 Topt 31.52 32.14 30.59 31.45 32.15 0.95 0.19 0.99 0.80 0.19 -1.20 -1.02 -1.21 -1.05 -1.02 r2 0.911 0.852 0.734 0.852 0.923 RSS ( 10-4) 30.00 0.68 30.00 0.79 0.12 Lactin AIC -73.12 -63.89 47.12 -62.43 -59.79 Rm 0.479 0.062 0.720 0.146 0.038 Topt 30.32 31.37 29.50 30.45 30.84 T0 7.84 9.68 8.19 9.16 9.16 r2 0.792 0.976 0.923 0.872 0.863 Taylor RSS ( 10-4) 180.0 3.2 250.0 17.6 1.05 67

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Table 2-6. continued Model Parameter Eggs Larvae Prepupae Pupae Total development AIC -57.19 -67.49 53.91 -80.45 -102.64 a( 10-6) -10.0 -2.1 -10.0 -5.1 -1.2 b( 10-3) 1.10 18.00 1.03 45.00 11.00 c -0.0341 -0.0057 -0.0313 -0.0140 -0.0034 d 0.466 .077 0.045 0.195 0.047 e -2.33 -0.37 -2.49 -0.97 -0.23 r2 0.925 0.935 0.964 0.926 0.924 RSS ( 10-4) 80.00 0.37 130.00 2.82 2.00 Polynomial AIC -61.31 -43.12 56.45 -72.42 -67.31 K, thermal constant or degree da ys; T, rearing temperature; T0, lower temperature threshold; Tm, upper temperature threshold; Topt, optimum temperature; a, b, c, d, e, empirical constants; mx, growth rate at given base temperature; developmental rate at optimal temperature; number of degrees over the base temperature over which thermal inhibition becomes predominant; empirical constant which forces the curve to intercept the y-axis at a value below zero; Rm, is the maximum developmental rate. 68

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Figure 2-1. Larval, pupal and adult stages of lesser cornstalk borer: A) Larva (sixth instar), B) Pupa, C) Adul t male, D) Adult female 69

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Figure 2-2. Experimental set-up for lesser cornstalk borer larval development on young sugarcane shoots: A) Upr ooted sugarcane plants, B) Seed pieces removed, C) Paper towel wrapped around the plant base and kep moist, D) Five shoots placed in each plastic container with a layer of vermiculite underneath. 70

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Figure 2-3. Relationship bet ween egg developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on sugarcane. 71

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Figure 2-4. Relationship betw een larval developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on sugarcane. 72

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Figure 2-5. Relationship betw een prepupal developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on sugarcane. 73

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Figure 26. Relationship between pupal developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on sugarcane. 74

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Figure 2-7. Relationship between tota l (egg deposition to adult emergence) developmental rate (d-1) and temperature (C) with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimated by Briere-1 model (aT(T T0) (sqrt(Tm T))) for lesser cornstalk borer on sugarcane. 75

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CHAPTER 3 LIFE TABLE STUDIES OF LESSER CORNSTALK BORER, ELASMOPALPUS LIGNOSELLUS (LEPIDOPTERA: PYRALIDAE) ON SUGARCANE Introduction The lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), is a polyphagous pest and widely distributed in United States and Central and South America (Heinrich 1956, Genung and Green 1965, Chang and Ota 1987). It is a semi-subterranean pest that attacks sugarcane at or below the so il level and causes dead hearts or symmetrical rows of holes in emerging leaves. Larval feeding damage reduces sugarcane photosynthesis, plant vigor, number of millabl e stalks, and sugar yield (Carbonell 1977). Reproductive studies of lesser cornst alk borer have been conducted on cowpeas (Luginbill and Ainslei 1917), peanuts (King et al. 1961), southern peas (Dupree 1965), soybean (Leuck 1966), and sugarcane (Carbonell 1978) as well as under an artificial diet (Stone 1968) under natural climatic conditi ons. In all these studies temperature and relative humidity (RH) were not held consta nt but varied with the climatic conditions. The effects of constant temperatur e (Mack and Backman 1984) on longevity and oviposition rate of lesser cornstalk borer on artificial diet were reported under controlled environmental conditions. However, quantitative information on life table parameters such as net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase ( ), mean generation time (T), and popul ation doubling time (DT) of lesser cornstalk borer was not published in their study. Life tables are powerful tools for anal yzing and understanding the impact of external factors such as te mperature on the growth, surviv al, reproduction, and rate of increase of insect populations (Sankeperumal et al. 1989). The r is used to determine the population increase under optimum conditions, which can vary with the larval host or 76

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diet. It was reported that larval diet had a significant effect on the survival of Spodoptera litura (Fabricius) (Lepidoptera: Noctuida e) (Sankeperumal et al. 1989) and the fecundity of Helicoverpa assulta Guenee (Lepidoptera: Noctuidae) (Wang et al. 2008). To predict lesser cornstalk borer popul ation on sugarcane, it was important to study its life history on the same host. D ue to lack of life table studies of lesser cornstalk borer on sugarcane, we measured the effect of diffe rent constant temperature conditions on reproductive parameters (pre-ovi position, oviposition, post-oviposition periods, and fecundity) and lif e table parameters (r, R0, T, and DT) of lesser cornstalk borer reared on sugarcane. Materials and Methods Reproductive Parameters Pre-oviposition, oviposition, post-ovi position periods, and fecundity for lesser cornstalk borer were determined at nine constant temperatures [13, 15, 18, 21, 24, 27, 30, 33, and 36 C ( 0.05 C)] at 14:10 (L:D ) h and 65-70% RH in temperature controlled chambers to construct time-specific life tables. Ten male:female pairs of newly emerged adults < 12 h old were first rel eased into each of three oviposition cages (17 17 17 cm) for mating. Adults we re obtained from the immatures reared on sugarcane and used for developmental studies at the same temperatures and relative humidity as indicated above in temperatur e control chambers (Sandhu et al. 2010a). Adults were provided with 10% honey soluti on for feeding. Afte r 24-h, pairs were moved to transparent plastic cylinders ( one pair / cylinder) (11 cm length and 5 cm diameter; Thorton Plastics, Salt Lake City, UT) lined with tubul ar synthetic stockinette as an oviposition substrate. Thirty pairs from each of three generations were tested over time at each temperature. Adults were obser ved daily for pre-oviposition, oviposition, 77

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and post-oviposition periods. The stockinette was replaced daily during oviposition periods and the eggs were counted using a hand lens. The orange-colored eggs were easily observed against the white background of the stockinette material. Fecundity was reported as the number of eggs deposited by an individual fema le during her entire life period. Age-specific female survival (lx, percentage of females alive at specific age x) and age-specific fecundity (mx, number of female offsprings produced by a female in a unit of time) were calculated for eac h day (x) they were alive. The lx and mx values were calculated using results from lesse r cornstalk borer immature development, survivorship and sex ratio studies conducted concurrently under the same environmental conditions (Sandhu 2010a). Age specific fecundity was calculated as (f / (m + f)) n, where f = number of females, m = number of males, and n = number of offspring. Mean lx and mx were calculated for each cohort of 10 females. Data from pairs of adults in which one or both sexes died before the start of egg deposition were excluded from data analysis. Age-specific su rvivorship curves were constructed using mean lx and mx values for cohorts at each temperature treatment. Life Table Parameters The age-specific life table method was used to calculate the life table parameters for lesser cornstalk borer (Birch 1948). The in trinsic rate of increase (r) was calculated using the Euler-Lotka equation ( e-rx lxmx = 1). Mean lx and mx values were used to calculate net reproductive rate (R0 = lxmx, mean number of female offspring / female), finite rate of increase ( = antiloger, the number of times t he population multiplies in a unit of time), mean generation time (T = (xlxmx) / (lxmx), mean age of the mothers in a 78

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cohort at the birth of female offspring), and population doubling time (DT = ln (2) / r, the time required for the population to double). Model Evaluation A non-linear distribution was observed when r was plotted against the temperature treatments. PROC NLIN was used to fit si x non-linear regression models (Table 3-1) to the data (SAS Institute 2008). Sigma Plot (S ystat Software, Inc., San Jose, CA) was used to plot regressions of non-linear models. Models for testing were chosen based on their previous use in insect life table studies. The models were evaluated based on the coefficient of determination (r2), adjusted coefficient of determination (r2 adj., a modification of r2 that adjusts for the num ber of explanatory terms in the model), the residual sum of squares (RSS), and the Akai ke Information Criterion (AIC) (Akaike 1974). The r2 and r2 adj. indicate better fits with higher values, whereas RSS and AIC indicate better fits with lower values. The value of AIC wa s calculated using the formula AIC = n ln(SSE/n) + 2p, wher e n is the number of treatm ents, p is the number of parameters in the mode l, and SSE is the sum of the squared error. Data Analysis PROC MIXED (SAS Institute 2008) was used to analyze the variance due to potential covariance structure associated with taking repeated measures over time at each temperature. Normality of the data was tested with Shapiro-Wilk normality test (Shapiro and Wilk 1965). The oviposit ion cages were treated as cohorts and replications through time were treated as gener ations for data analysi s. Temperatures, cohorts, generations, and their interactions were used in the analysis of variance models. Generations were used as the r epeated variable and the cohorts were nested under temperature in the repeat ed measures statement. Seve ral covariance structures 79

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were fitted to the data. The unstructured covariance type fit well and was used for the analysis (Littell et al. 1998). Data for each pair of adults were used for analysis of effects of temperature, cohor t, and generation for pre-ovipos ition, oviposition and postoviposition periods and fecundity. Mean daily values by cohort were used for analysis of effects of temper ature and generation on lx and mx. The percentage of females alive at age x (lx) was arcsin square root transformed for normality purpose before analysis and retransformed for presentation purposes. The Tukeys HSD test (SAS Institute 2008) was used for means separation with = 0.05. Results Reproduction Temperature had a significant effect on the lengths of the pre-oviposition, oviposition, and post-oviposition periods of lesser cornstalk borer (Table 3-2). Cohorts, generations and the modeled interact ions were not significant so urces of variation in the models for any of these periods. Theref ore, data were pooled across cohorts and generations to calculate means for these periods. Mean pre-oviposition period decreased with increase in tem perature from 9.7 d at 13 C to 2.3 d at 33 C (Table 33). Mean oviposition period was longest (5.6 d) at 27 C and decreased with increase or decrease from 27 C. However, the post-oviposition period was shortest at 27 C (2.6 d) and increased with increa se or decrease from 27 C. Fecundity was also significantly affect ed by temperature (Table 3-2). Cohort, generation and modeled interactions were not si gnificant sources of variation in the fecundity model. Therefore, fecundity data was pooled across cohorts and generations to calculate mean fecundity at each temperat ure. Fecundity increased with increase in 80

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temperature from 13 C to 30 C and decre ased at 33 and 36 C (Table 3-3). Mean fecundity ranged from 29.2 eggs ( 13 C) to 165.3 eggs (30 C). Life Table Parameters Temperature had a significant effect on lx and mx values. Generations and the modeled interactions did not pr ovide significant sources of variation in the models for lx and mx (Table 3-4). Therefore, data were pooled across generations to calculate means for these periods. Both lx and mx increased with increase in temperature from 13 C to 30 C and decreased at 33 and 36 C (figs. 3-1a to 3-1i). Temperature had a significant effect on the life table parameters r, R0, T, and DT (Table 3-4). Generations and the modeled interactions were not significant sources of variation in the models for these param eters. Therefore, data were pooled across generations to calculate means for t hese periods. The values for r, R0, T, and DT calculated at tested temperatur es are presented in Table 3-5. The value of r increased with increase in temperature fr om 13 C (0.02) to 30 C (0.14) and then decreased at 36 C (0.07). Similarly, R0 was greatest at 30 C (65.2) an d lowest at 13 C (9.2). The value of T was greatest (130.5 d) at 13 C and lowest (27.6 d) at 33 C. The value of DT decreased with increase in temperature from 40.8 d at 13 C to 5.1 d at 30 C. The value of increased with increase in temperature from 1.02 at 13 C to 1.14 at 30 C and then decreased at 36 C. Model Evaluation The fitted coefficients and the model evaluation parameters are presented in Table 6. The Briere-2 model was the best fit to the data with greatest r2 (0.9833) and r2 adj.(0.9733), and lowest RSS (0.0003) and AIC (96.14) values. The Logan-6, Lactin, 81

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Taylor, and polynomial (fourth order) models ex plained less variation than the Briere-1 and Briere-2 models. The fitted curve for the Briere-2 model representing the relationship between r and temperature for lesser cornstalk borer on sugarcane is presented in fig. 3-2. Discussion Reproduction The values for the reproductive paramet ers on sugarcane fell mostly within the ranges of those determined for E. lignosellus on other crops. The mean ( SEM) preoviposition period found in this study (2.3 0.1 d at 33 C to 9.7 0.1 d at 13 C) is similar to the value of 2.8 d reported by Stone (1968) for E. lignosellus on an artificial diet. The mean oviposition period on sugarcane (1.2 0. 1 d at 13 C to 4.6 0.1 d at 27 C) was shorter than those reported on an artificial diet (10.4 d, Luginbil l and Ainslei 1917; 11.8 d, Stone 1968; and 6.4 d, Simmons and Lynch 1990). The results of our study on oviposition period fit within the range determined by Dupree (1965) on southern pea (Mean: 4.1 d, range 1 to 9 d). The 4.7 d post-oviposition period reported by Leuck (1966) on soybean is consistent with that found on sugarcane (2.5 0.1 to 5.9 0.1 d). Lesser cornstalk borer mean fecundity (num ber of eggs/female) reported in earlier studies was 192 on cowpeas (Luginbill and Ainslei 1917), ranged from 124 to 129 on soybean (King et al. 1961, Dupree 1965, and Leuck 1966), and ranged from 67 (Calvo 1966) to 419.5 on artificial diet (Stone 1968). Mean fecundity in a ll of these reports except Stone (1968) fell in t he range reported in present st udy (29 to 165 eggs). The results of our study are similar to t hose of Mack and Backman (1984) who reported an increase in fecundity with an increase in temperature from 17 to 27.5 C, peaks at 27.5 82

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and 30.5 C, and large decreases at 17 and 35 C On sugarcane, fecundity increased with an increase in temperatur e from 13 C (29 1 eggs / female) to 30 C (165 6 eggs / female), and then decreased at 33 C and 36 C. Life Table Parameters Life table parameters repor ted for other pyralid pests and lesser cornstalk borer are presented in Table 7 for comparison purposes. Life table parameters of sugarcane borer, Diatraea lineolata (F.) on corn and artificial diet were not significantly different when compared at 25 C (Rodrguez Del Bosque et al. 1989), but r and were lower than for lesser cornstalk borer on sugarcane. At 30 C on artificial diet, sugarcane borer and Mexican rice borer, Eoreuma loftini (Dyar) (Stamou et al 2002), recorded lower r and and higher T and DT paramet ers than those reported in our study. Mexican rice borer had a greater R0 than lesser cornstalk borer i ndicating its high reproductive potential, but the intrinsic rate of increas e for Mexican rice borer was lower on an artificial diet than for lesse r cornstalk borer on sugarcane. The life table parameters for E. lignoselus on sugarcane are com parable to those of Ephestia kuehniella Zeller (AmirMaafi and Chi 2006) on artificial diet at 28 C. The life table parameters for Cactoblastis cactorum (Berg) (Legaspi and Legaspi 2007) on arti ficial diet at 30 C show its low reproductive potential compared to lesser cornstalk borer on sugarcane. The high reproductive potential of lesser cornstalk bor er compared to other sugarcane pyralid pests, especially at 27 and 30 C, indicates t he importance of its early detection or prediction in the field. Model Evaluation The same mathematical models used in the present study were also used to determine the relationship between temperature and r for Sitotroga cereallela (Olivier) 83

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(Lepidoptera: Gelechiidae) on corn, Zea mays L. (Hansen et al. 2004), and for Halyomorpha halys (Stal) (Hemiptera: Pentatomi dae) (Nielsen et al. 2008) on green beans, Vigna radiata (L.) Wilczek. The Briere-1 model was reported as the best fit for both of these insects compared to the Briere-2 model for lesser cornstalk borer on sugarcane based on the ev aluation parameters (r2, r2 adj., RSS, and AIC values). The Briere-2 model was the best model for describing the positively curvilinear response of lesser cornstalk borer to temperature up to the optimal temperatur e and sharp decline immediately following the optimum of any of the tested models. Differences in model performance reported in the lit erature were possibly caused by differences in thermal adaptation of the insect species or by di fferences in the host crops and diets. Model Application Population predictions for lesser cornst alk borer can begin to be made based on the results of this study to improve their management in sugarcane. The equation of the best fitted model (Briere-2 model) can be used to calculate r at any given temperature (T). Based on the initial population (N0) and value of r, the Malthusian equation Nt = N0ert (where Nt is the population at time t, N0 is initial population, r is intrinsic rate of increase, and t is time period) can be us ed for population predict ions (Stimac 1982). Using air temperature data fr om two weather stations (B elle Glade and Clewiston), FL within the predominant sugarcane cultivation area of southern Florida (University of Florida IFAS extension 2009), lesser cornst alk borer populations were predicted to increase by <2 to >8 times (Fig 3-3) per month during different months of the year. Commercial sugarcane is reproduced veget atively and new fields are normally planted September through December in Florida. As a result, late planted fields are particularly susceptible to lesser cornstalk borer attack. The mo st vulnerable shoots 84

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emerge January through May as the lesser corn stalk borer population growth potential increases from 2x to 8x and can reduce st and establishment. This is also the dry season for southern Florida and dry soil surfac es are ideal for lesser cornstalk borer oviposition and immature survival. S ugarcane is harvested annually and ratooned two to more times in southern Florida. S hoots produced in early harvested fields (midOctober through November) ar e under less lesser cornstalk borer population pressure following the wet summer months as lesser cornstalk borer population growth potential is declining and at a low during the winter m onths. Shoots emerging in fields harvested mid-December through April face the same elevated lesser cornstalk borer damage potential as plant cane fields. However, because stools in ratooned sugarcane are already established, early, strong shoot esta blishment is more of a concern for yield reduction than stand establishment. Conclusion Life table analysis shows that the lesser cornstalk borer has high potential to increase its population level in sugarcane quickl y. Temperatures of 27 and 30 C were most favorable for reproduction and survival. The results of this temperature-dependent study on reproduction (pre-oviposition, ovip osition, post-oviposition periods, and fecundity) and estimation of life table param eters provide important information for predicting outbreaks of lesser cornstalk borer which can improve its management in sugarcane. Additional factors remain to be estimated and the models require field testing before they can reach their full potential. For example, elevated soil moisture at the soil surface plays an important role in reduced oviposition and larval survival under field condition (Smith and Ota 2002). Larval parasitoids and predators may also play an 85

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important role in regulating E. lignosellus population growth in sugarcane (Falloon 1974). 86

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87 Table 3-1. Mathematical equations of development models tested to describe the relationship between temperatur e and intrinsic rate of natural increase (r) of E. lignosellus on sugarcane Model Equation References Linear K/ (T T0) Roy et al. 2002 Briere-1 aT(T T0) (sqrt(Tm T)) Briere et al. 1999 Briere-2 aT(T T0) ((Tm T) (1/d)) Briere et al. 1999 Logan-6 mx(exp( T) exp( Tm (Tm T)/ )) Logan et al. 1976 Lactin exp( T) exp( Tm ((Tm T)/ )) + Lactin et al. 1995 Taylor Rm exp(-.5((T Topt)/T0)2) Taylor 1981 Polynomial (4th order) a(T)4 + b(T)3 + c(T)2 + d(T)+ e Lamb et al. 1984 K, thermal constant or degree da ys; T, rearing temperature; T0, lower temperature threshold; Tm, upper temperature threshold; Topt., optimum temperature; a, b, c, d, e, empirical constant; mx, growth rate at given base temperature; developmental rate at optimal temperature; number of degrees over the base temperature over which thermal inhibition becomes predominant; empirical constant which forces the curve to intercept the yaxis at a value below zero; Rm, is the maximum dev elopmental rate.

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88 Table 32. Analysis of variance for effects of tem perature, cohort and gener ation on reproductive parameters of E. lignosellus on sugarcane F df, and P mperature, cohort and gener (PROC MIXED, SAS Institute 2008) values represent ANOVA of te ation treatments within a reproductive stage Pre-oviposition Oviposition Post-oviposition Fecundity Source df F P df F P df F P df F P Model 80 80 80 80 523.10 < 0.0001 Error 570 236.70 < 0.0001 570 58.30 < 0.0001 570 40.00 < 0.0001 570 Temp. 8 236.10 < 0.0001 8 579.60 < 0.0001 8 395.10 < 0.0001 8 457.80 < 0.0001 Cohort 8 1.05 0.3511 8 0.19 0.8291 8 0.77 0.4640 8 2.15 0.2420 Generation 2 0.78 0.5881 2 0.18 0.9820 2 0.84 0.5380 2 3.04 0.1941 T x C 64 0.69 0.9670 64 0.41 1.0000 64 0.51 0.9990 64 1.54 0.6412 T x G 16 0.74 0.6421 16 0.69 0.5240 16 0.76 0.6120 16 2.15 0.3540 C x G 16 1.02 0.3950 16 1.11 0.4520 16 1.25 0.4550 16 1.89 0.5411 T x C x G 128 0.89 0.5490 128 0.86 0.5131 128 0.78 0.6290 128 0.97 0.6242

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89 Table 3-3. Mean ( SEM) pre-oviposition, oviposition, post-oviposition periods and fecundity of E. lignosellus on sugarcane under laboratory conditions Temp (C) Pre-oviposition (d) Oviposition (d) Postoviposition (d) Fecundity (eggs / female) 13 9.7 0.1a 2.2 0.1f 5.9 0.1a 29.2 3.1f 15 7.2 0.1b 2.8 0.1e 5.3 0.1b 42.3 4.2e 18 5.8 0.1c 4.5 0.1c 4.2 0.1c 51.1 4.7d 21 3.5 0.1d 4.5 0.1c 4.0 0.1d 56.3 4.9d 24 2.9 0.1e 4.8 0.1b 3.8 0.1e 97.5 5.3c 27 2.7 0.1f 5.6 0.1a 3.2 0.1fg 158.4 6.1a 30 2.5 0.1g 4.5 0.1c 3.3 0.1f 165.3 6.5a 33 2.3 0.1h 3.2 0.1d 3.1 0.1g 110.2 5.1b 36 4.4 0.1d 2.8 0.1e 2.5 0.1h 62.3 4.2d F 249.20 593.49 439.28 523.10 df 8, 570 8, 570 8, 570 8, 570 P < 0.0001 < 0.0001 < 0.0001 < 0.0001 F df, and P values represent ANOVA of te mperature, coho rt and generation treatments within a reproductive st age (PROC MIXED, SAS Institute 2008). Means within a column followed by the same letters are not significantly different (Tukeys test, = 0.05).

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90 Table 34. Analysis of variance for effects of tem perature, cohort and generation on life table parameters for E. lignosellus on sugarcane Source df F P df F P df F P df F P lx mx r R Model 26 26 26 812.67 < 0.0001 26 218.39 < 0.0001 Error 333 15.94 < 0.0001 333 5.11 < 0.0001 54 54 Temp. 8 50.19 < 0.0001 8 16.05 < 0.0001 8 263.09 < 0.0001 8 709.79 < 0.0001 Generation 2 0.52 0.5972 2 0.13 0.8805 2 1.04 0.3608 2 0.50 0.6071 T x G 16 0.75 0.7384 16 0.26 0.9984 16 0.91 0.5605 16 1.07 0.4079 T DT Model 26 26 26 255.10 < 0.0001 Error 54 250.20 < 0.0001 54 382.04 < 0.0001 54 Temp. 8 461.50 < 0.0001 8 124.16 < 0.0001 8 829.30 < 0.0001 Generation 2 0.61 0.5942 2 0.20 0.8198 2 0.12 0.8906 T x G 16 0.72 0.4891 16 0.57 0.8929 16 0.08 1.0006 r, intrinsic rate of natural in crease (female/female/day); R0, net reproductive rate (fem ale/female/generation); T, generation time (d); DT, popul ation doubling time (d); finite rate of increase (female/female/day). F df, and P values represent ANOVA of tem perature, cohort and generat ion treatments within a life table parameter (PROC MIXED, SAS Institute 2008).

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Table 3-5. Life table parameters of E. lignosellus on sugarcane at nine constant temperatures Temp. r R0 T DT 13 0.02 0.005f 6.5 0.9i 130.5 2.9a 40.8 1.1a 1.02 0.05g 15 0.03 0.006 f 13.8 1.1h 102.6 2.4b 26.7 1.0b 1.03 0.04f 18 0.04 0.004e 16.4 1.2g 77.9 1.8c 18.2 0.9c 1.04 0.05e 21 0.05 0.005d 19.3 1.5f 55.3 1.7d 12.8 0.7d 1.06 0.05d 24 0.08 0.006c 37.9 0.7d 45.7 1.3e 8.7 0.5f 1.08 0.06c 27 0.12 0.007b 63.2 1.4b 30.1 0.8g 5.9 0.3g 1.12 0.07b 30 0.14 0.006a 65.2 1.3a 30.9 0.9g 5.1 0.3h 1.14 0.09a 33 0.13 0.006a 39.4 0.6c 27.6 0.7h 5.2 0.2h 1.14 0.09a 36 0.07 0.005c 21.1 0. 5e 42.1 1.2f 9.5 0.8e 1.08 0.07c F 263.9 709.8 124.2 82.9 46.2 df 8, 80 8, 80 8, 80 8, 80 8, 80 P < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 r, intrinsic rate of natural in crease (female/female/day); R0, net reproductive rate (female/female/generation); T, generation time (d); DT, population doubling time (d); finite rate of increase (female/female/day). F df, and P values represent ANOVA for temper ature treatments wit hin a life table parameter (PROC MIXED, SAS Institute 2008). Means within a column followed by the same letters are not significantly different (Tukeys test, = 0.05). 91

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Table 3-6. Fitted coefficients and eval uation indices for si x non-linear models tested to describe the relationship between intrinsic rate of natural increase (r) of E. lignosellus and temperature Non-linear models Parameters Briere1 Briere-2 Logan-6 Lactin Taylor Polynomial (4th order) a ( 10-5) 9.00 10.00 ----0.112 b ( 10-3) -----7.000 c ------0.003 d 2.00 4.10 ---0.037 e ------0.213 mx --0.01 -----0.09 0.01 -----0.19 ---Rm ----0.04 -T0 12.09 9.89 --9.39 -Tm 36.98 36.09 36.23 36.45 --Topt. 33.12 32.57 33.44 32.68 31.02 -r2 0.9563 0.9833 0.6101 0.5614 0.6525 0.6213 r2 adj 0.9417 0.9733 0.4210 0.4021 0.5142 0.4563 RSS 0.0007 0.0003 0.0047 0.0059 0.0079 0.0062 AIC -89.67 -96.14 -68.63 -39.81 -42.65 -43.13 a, b, c, d, e, empirical constants; mx, growth rate at given base temperature; developmental rate at optimal temperature; number of degrees over the base temperature over which therma l inhibition becomes predominant; empirical constant which forces the curve to interc ept the y-axis at a value below zero; Rm, is the maximum developmental rate; T0, lower temperature threshold; Tm, upper temperature threshold; Topt, optimum temperature; --, absence of coefficient in the model. 92

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Table 3-7. Life table parameters for Pyralidae (Lepidoptera) pests on artificial diet and lesser cornstalk borer on sugarcane in this study Life-table parameters Pest Temp. (C) Host r R0 T DT Source D. lineolata 25 Corn 0.053 15.6 51.5 -1.06 Rodrguez Del Bosque et al. 1989 D. lineolata 25 Artificial diet 0.054 19.92 55.37 -1.06 Rodrguez Del Bosque et al. 1989 D. saccharalis 30 Artificial diet 0.066 15.5 41.6 10.5 1.06 Stamou et al. 2002 E. loftini 30 Artificial diet 0.096 122.0 50.2 7.2 1.10 Setamou et al. 2002 E. kuehniella 28 Artificial diet 0.137 11.9 18.2 -1.14 Amir-Maafi and Chi 2006 C. cactorum 30 Artificial diet 0.056 43.7 67.1 12.3 1.05 Legaspi and Legaspi 2007 E. lignosellus 30 Sugarcane 0.14 65.2 30. 9 5.1 1.14 Present study r, intrinsic rate of natural increase; R0, net reproductive rate; T, generation time; DT, population doubling time; finite rate of increase. 93

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A B Figure 3-1. Relationship betw een the temperature (C) and age-specific survival, lx (solid line), and age specific daily fe cundity, mx (dashed line), for E. lignosellus at the tested temperatures. A) 13 C, B) 15 C, C) 18 C, D) 21 C, E) 24 C, F) 27 C, G) 30 C, H) 33 C, I) 36 C. 94

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C 21C D Figure 3-1 continued. 95

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E F Figure 3-1 continued. 96

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30 C G H Figure 3-1 continued. 97

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I Figure 3-1 continued. 98

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Figure 3-2. Relationship betw een temperature (C) and intrinsi c rate of natural increase (r) for E. lignosellus with mean ( SEM) lower (T0) and upper (Tm) developmental thresholds estimat ed by Briere-2 model aT(T T0) ((Tm T) (1/d)) for E. lignosellus on sugarcane. 99

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Figure 3-3. Predicted population growth of E. lignosellus on sugarcane based on the Briere-2 model and average monthly te mperatures at two locations in southern Florida. 100

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CHAPTER 4 COMPENSATORY RESPONSE OF SUGARCANE TO ELASMOPALPUS LIGNOSELLUS DAMAGE Introduction Compensation is the process by which plants respond positively to an insect injury (Bardener and Fletcher 1974) and decr ease the negative effect on yield (Pedigo 1991). Compensatory growth can result from the suppression of growth regulating substances (Dillewijn 1952), or reallocation of resources within individual plants following herbivory, depending on source-sin k relationships (Larson and Whitham 1997, Stowe et al. 2000). The growing point suppresses bud development through growth regulating substances, and removal of the primary shoot can alter the effect of these substances allowing more tillers to develop. In source-sink relationships, sources are photosynthetic organs or storage tissues (e.g ., leaves) for net carbon gain, while sinks are the organs used for growth and reproduction (i.e., apical meri stems, flowers and fruits) (Whitham et al. 1991). The source-sin k relationship can be modified by removing either the source or sink through herbivory Honkanen et al. ( 1994) reported that the damage to apical bud in Scots pine ( Pinus sylvestris) resulted in significant increase in mass and length of needles in lateral shoots. Compensatory plant growth in response to insect damage caused at early growth stages has been reported in many field crops. For example, rice co mpensates for injury at the vegetative stage by the stem borer Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) (Rubia et al. 1990) by producing new vegetative (Soejitno 1979, Tian 1981, Akinsola 1984, Viajante and Heinrichs 1987) and reproductive tillers (Luo 1987). Studies have also shown that low insect in festation levels at early growth stages may 101

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increase plant yield in field beans (Banks and Macaulay 1967), wheat (Gouch 1947, Bardener 1968), potato (Skuhravy 1968), and cotton (Kincade et al. 1970). Florida is the leading sugar cane producing state in the U. S. with 401,000 acres of sugarcane valued at $398.9 milli on dollars in 2008 (USDA 2008) The majority of the sugarcane acreage is grown in Palm Beac h, Martin, Hendry, and Lee counties in southern Florida. Sugarcane is vegetativel y propagated by planting mature stalks. Buds start developing shoots soon after pl anting. These shoots are called mother shoots or primary shoots. Primary shoots have many small internodes each carrying a lateral bud. These lateral buds develop into secondary shoots that in turn may produce tertiary shoots (Dillewijn 1952). Sugarc ane has a great capacity to compensate for damage to young shoots. Compensation abil ity depends on the plant variety and age of the plant at which damage occurred, wit h the greatest compensation in young sugarcane and diminishing with plant age. Demandt (1929) reported 50% compensatory growth of sugarcane in respon se to mechanically damaged shoots. He showed that this compensation was partly due to the production of new tillers, and partly due to survival of the stalks which otherwise would have died due to lack of nutrients in the presence of the primary shoot. Wen and Shee (1948) later showed that mechanical removal (topping) of the primary shoots increased the number of m illable stalks by 11.3% and sugarcane yield by 25.9%. Lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae), is a serious pest of sugarcane in southern Flor ida, particularly on silica soils. There are multiple varieties of sugarcane grown in this area (Rice et al. 2009) that are attacked by lesser cornstalk borer at di fferent growth stages. Larva e enter the young shoot of 102

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sugarcane causing two types of damage (Fig. 4-1) Larvae that reach the center of the shoot and damage or sever the youngest leav es produce dead hear t symptoms. Nonlethal damage is caused when larvae only chew a few millimeters into the shoot and becomes evident when the leaves push out to reveal one to several symmetrical rows of holes (Schaaf 1974, Carbonell 1 978). We observed a third type of damage in which shoots died in response to larval E. lignosellus feeding and did not produce tillers. However, initial feeding damage does not always result in stand or yield loss. Carbonell (1978) reported 27.8% recovery in plant c anes and 48.1% recovery in stubble canes in response to E. lignoselus damage. Information on variety specific sugarcane recovery to E. lignosellus damage would be useful for the i ndustry in their variety selection program. This information is also important for developing damage thresholds for use in integrated management of this pest in the numerous susceptible grass and vegetable crops grown throughout the southeastern United St ates. The objective of this study was to document variety and age specific feeding damage in sugarcane by lesser cornstalk borer larvae and the potential for damaged pl ants to compensate for early season damage. Materials and Methods Effects of damage caused by lesser corn stalk borer on sugarcane growth and yield were evaluated in two, 11-mo. greenhouse studies during 2008 (January to November) and 2009 (November 2008 to September 2009) conducted at the Everglades Research and Education Center (EREC), Belle Glade, Florida. The sugarcane varieties CP78-1628, CP89-2143 and CP88-1762 were selected for this study. These varieties occupy the gr eatest acreage grown on Immokalee fine sand (sandy soil) where lesser cornstalk borer is considered to be a major perennial problem 103

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(Rice et al. 2009). CP89-2143 and CP88-1762 were also ranked as first and second in total Florida sugarcane acreage. Three early growth stages (3-, 5-, and 7-leaf stage) were selected for infestation with lesse r cornstalk borer larvae based on damage reports during the first 2-3 m onths of sugarcane growth (C arbonell 1978). These three selected growth stages were present approxim ately 3, 5, and 8 wk after primary shoot emergence. Production of Sugarcane Plants Mature stalks of each variety were harvested from fields at the EREC to obtain viable buds for planting. Stalks were cut into 10 cm-long seed pieces each with one bud (i.e., single eye sets) and planted in plas tic trays (50 36 9.5 cm) filled with Immokalee fine sand to germinate the buds and produce shoots. Immokalee fine sand was used as a medium for plant growth throughout the experiment, because lesser cornstalk borer causes more damage in s andy soil than muck soil, and Immokalee fine sand is one of the major sandy soils in the sugarcane growing area around Lake Okeechobee in south central Florida. Two days after emergence, uniform sized seedlings were selected and transplanted to 19.0 liter (5 gal) buckets (two seedlings per bucket) filled with Immokalee find sand. Plants were fertilized by adding 50 g of ammonium sulfate and 20 g of a balanced granular fertilizer (14-14-14) to the soil of each bucket at planting time and again every 3 mo. until harvest. Irrigation was applied every 2 d. Insect Rearing Insects used in this study were obtained from a laboratory colony of lesser cornstalk borer maintained at EREC. The co lony was started 4 mo. before the start of the experiment, by using larvae and adults of E. lignosellus collected from sugarcane 104

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fields at Belle Glade and Moor e Haven, Florida. The col ony was maintained on a wheat germ and soy flour based artificial diet as described in Sandhu et al. (2010a). Third instar larvae were used to infest sugarcane pl ants. To produce larvae for the trial, first and second instar larvae were removed from artificial diet and reared on 3-4 leaf stage shoots of respective sugarcane varieties to avoid the effect of host change on larval feeding. The choice to use third instar fo r infestation was based on preliminary trials on green house plants, where it was observed that first and second instars had high mortality and their feeding on leaves did not cause major damage. Third instar larvae move from leaves to the soil to feed on shoots and tillers. Experiment Design A randomized complete block design with a 3 4 factorial arrangement was used during both experiment years to evaluate sugarcane response to E. lignosellus feeding damage. The factors were three sugarcane varieties (CP 78-1628, CP88-1762, and CP89-2143) and three leaf st ages infested plus one control (i.e., no infestation and infestation at 3-, 5-, and 7-leaf stages). The combinations of these factors (3 4) were applied randomly to the 12 buckets in each block. The buckets in each block were arranged in 2 rows of 6 buckets each. Each block was replicated 12x in 2008 and 15x in 2009. Four, third instar (6-7 d old) larvae conditioned on sugarcane as above were released near the base of plants in each bucket with the aid of a camel hair brush at the respective leaf stages. The number of larvae per bucket was selected based on preliminary trials on greenhouse plants. S ugarcane in the buckets was exposed to a single generation of lesser cornstalk borer. After completion of the larval stage, pupae were collected and returned to the colony by removing and straining the top 6 cm of soil. Timing for the completion of the larval stage was estimated based on the results of 105

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temperature-dependent developmental studies on sugarcan e seedlings in the laboratory (Sandhu et al. 2010a). Damage Assessment Feeding damage was recorded for primar y shoots and tillers in each bucket. Secondary and tertiary shoots will be referred to as tillers in this report. The number of dead hearts, number of shoots with symmetrical rows of holes in leaves, and number of dead plants per bucket were recorded weekly st arting one week after infestation at each leaf stage. Plants were c ounted as dead heart if feeding l ead to chlorosis and necrosis of only the primary shoot. A plant with damage that led to necrosis of both primary shoot and tillers and the cessation of tiller production was counted as a dead plant. Buckets were first observed for dead pl ants, then dead hearts and then holes in the leaves. Plants counted as dead could not be counted as dead hearts, and plants with dead hearts could not also be counted as plant with holes in leaves. Mean percentage of plants with dead hearts, holes in the leaves, and dead plants were calculated using the final observation (4 wk after infest ation) on all damaged and undamaged shoots and tillers per bucket. Total damage by lesser cornstalk borer was calculated as the summation of dead hearts, holes in the leaves and dead plants per bucket. The number of tillers per bucket was counted 4 mo. after emergence to account for varietal and leaf stage differences in tiller production. Sugarcane Yield Assessment Sugarcane yield was determined using the number and weight of millable stalks, and the sucrose concentration of juice squeezed from those stalks. Millable stalks are primary shoots and tillers > 1. 5 m in height and are traditional ly counted 8 mo. after the first emergence of sugarcane shoots. Millable stalks are counted 3 mo. before 106

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harvesting, because lodging in sugarcane at harvest time interferes with determining the height and exact number of millable stalks. Millable stalks from each bucket were harvested 11 mo. after sugarcane emergence. Individual stalks were weighed separately, and sugarcane yield (Kg per bucket) was calculated as the product of the number of millable stalks and the mean stalk weight in each bucket. To determine sucrose concentration, two randomly sele cted millable stalks per bucket from each block were milled and crusher juice-analyzed for brix and pol values as described by Gilbert et al. (2008). Sucrose (Kg per bucket) was calculated according to the theoretical recoverable sugar method (Glaz et al. 2002). Data Analysis The data were analyzed using analyses of variance (ANOVA) (SAS Institute 2008). The data on response variables (dead hearts, holes in the leaves, dead plants, number of tillers, stalk coun t, cane yield and sugar yield) we re recorded for each bucket and analyzed for the effect of year, varieties, in fested leaf stages and their interactions. Proportionate data were arcsine transform ed before analysis and retransformed for presentation purposes. Ort hogonal contrasts were used to test for significant differences between specific factors (SAS Institute 2008) due to the incomplete factorial experimental design and for better comparisons between the untreated control and treatments. Results Damage The experiment year (df = 1, 300) was not a significant source of variation in the model for dead hearts ( F = 1.64, P = 0.2272), holes in the leaves ( F = 0.03, P = 0.8588), dead plants ( F = 0.01, P = 0.9880) or total damage ( F = 0.10, P = 0.7546). The data on 107

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damage types were pooled over the two year s and analyzed together by using year as a random effect with blocks nested within year (Table 4-1). The data were also pooled for two years to calculate the means for all damage types. No feeding damage was observed in the untreated controls and resulted in significantly higher percentages for all damage types for all variables than the untreated control. Dead hearts were the most co mmonly observed result of E. lignosellus feeding damage to sugarcane. Variety was a significant source of variation in the model for dead hearts (Table 4-1) with CP89-2143 (55.7 2.5) having a significantly greater percentage of plants with dead hearts than CP78-1628 (48.3 2.1) (Table 4-2). Leaf stage was a significant source of variati on in the model (Table 4-1); the earlier the plants were infested, the greater the resu lting dead heart symptoms were produced. Percentage of plants with dead he arts was greater in the sequence 3> 5> 7-leaf stage (Table 4-2). In all three varieties, pl ants infested at the 3leaf stage had a greater percentage of plants with dead hearts than those infest ed at the 7-leaf stage. Symmetrical rows of holes in the l eaves were the second most commonly observed damage by E. lignosellus feeding on sugarcane. Vari ety, leaf stage, and their interaction were significant sources of vari ation in the model for holes in the leaves (Table 4-1). CP78-1628 (34.3 3.1) had a significantly gr eater percentage of plants with holes in the leaves than CP89-2143 (23.0 2.9) (Table 4-2). In contrast to dead hearts, mean percentage of plants with holes in leaves was greater in late-infested (7leaf stage) than early-infest ed (3-leaf stage) plants. The mean percentage of plants with holes in the leaves at t he 7-leaf stage was significantly greater than at the 5-leaf stage, and more were found on pl ants infested at the 5-leaf stage than at the 3-leaf 108

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stage. In all three varieties, plants infest ed at the 7-leaf stage had a greater percentage of plants with rows of holes than t hose infested at the 3-leaf stage. Dead plants were the third ty pe of observed damage caused by E. lignosellus feeding on sugarcane, especially in variety CP 89-2143. Variety, leaf stage, and their interaction were significant sources of vari ation in the model for dead plants (Table 4-1). The mean percentage of dead plants in CP 89-2143 (16.0 3.4) was significantly greater than CP88-1762 (5.8 2.1) and CP781628 (3.2 1.2) (Table 4-2). The mean percentage of plants that died wh en infested at the 3(11.3 2.2) and 5-leaf (9.7 1.9) stages were significantly greater than at the 7-leaf (3.9 0. 6) stage. Infestation at the 3and 5-leaf stages in CP78-1628 and CP88 -1762, and 3-leaf stage in CP89-2143 produced greater percentages of dead plants t han infestation at the 7-leaf stage in respective varieties. In CP78-1628, no plan t died in late infested plants; however, early infestation in CP89-2143 caus ed the greatest percentage (19. 5 5.8) of plant deaths. The sum of plant feeding damage caused by E. lignosellus (dead hearts, holes in leaves and dead plants) was analyzed as the to tal damage. Variety had a significant effect on total damage percentage (Table 41) with CP89-2143 (94.7 3.1) having a greater percentage total dam age than CP78-1628 (85.8 2.4) and CP88-1762 (86.0 2.7) (Table 4-2). Leaf stage was also a significant source of variation in the model with greater total damage at the 3(90.1 2.0) and 5(90.8 2.1) leaf st ages than at the 7(85.5 1.7) leaf stage. Total damage in CP88-1762 and CP89-2143 did not vary significantly with infestation stage, but CP78-1628 had greater damage at the 3than at the 7-leaf stage. 109

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Tiller Production Experiment year significantly affe cted tiller production (df = 1, 300, F = 137.41, P < 0.0001) with approximately one additional tiller produced per bucket in 2009 than in 2008. Due to the significant year affect, the data were analyzed separately for 2008 and 2009 (Table 4-3). Variety, leaf stage and va riety leaf stage were all significant sources of variation in the model for number of tillers per bucket in both years. CP781628 and CP88-1762 produced significantly great er number of tille rs than CP89-2143 in both years (Tables 4-4, 4-5). Buckets infe sted at 3-leaf stage pr oduced significantly more tillers than those infested at 7-leaf stage in both years. In th e variety leaf stage interaction, E. lignosellus damage at the 3-leaf st age to CP78-1628 and CP88-1762 resulted in increased tiller production over the untreated controls in both years. However, CP89-2143 plants infested at all three leaf stages produced significantly fewer tillers than the untreated cont rol plants. In late infe sted plants, CP78-1628 produced more tillers than the other two varieties in 2008, but in 2009 both CP78-1628 and CP881762 produced more tillers than CP89-2143. Sugarcane Yield Traits Yield traits refer to the number of millable stalks, sugarcane yield and sucrose yield. The experiment year (df = 1, 300) was again a signific ant source of variation in the models for numbers of millable stalks ( F = 120.98, P < 0.0001), sugarcane yield ( F = 88.27, P < 0.0001), and sucrose yield ( F = 17.21, P < 0.0001). Therefor e, the data were analyzed separately for 2008 and 2009 (Table 4-3). The significant year affect resulted from greater yield traits in 2009 than in 2008, but the relative patterns for these traits among varieties, leaf stages and their interacti on were the same in both years. Overall there was approximately one extra stalk per bucket in 2009 than in 2008, which lead to 110

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0.75 kg increase in sugarcane yield and 0.05 kg increase in sucrose yield per bucket in 2009 than in 2008. Mean ( SEM) values of yield traits for 2008 and 2009 are presented in Table 4-4 and Table 4-5, respectively. Variations among varieties and leaf stages for millable stalk production were similar to tiller production, except that in festation at the 5-leaf stage of CP78-1628 resulted in production of significantly more milla ble stalks than the control. Variety, leaf stage and variety leaf stage were significant sources of variation in the model for the mean number of millable stalks per bucket duri ng both years (Table 4-3). Production of millable stalks in CP78-1628 and CP88-1762 was significantly greater than CP89-2143 in both years (Tables 4-4, 4-5). Similar to tiller production, early infestation produced a greater number of millabl e stalks than late infestation in both years. In the variety leaf stage interaction, E. lignosellus damage at the 3and 5-leaf stages in CP78-1628 resulted in increased millable stalk production over the untreated controls and those damaged at the 7-leaf stage in bot h years. In CP88-1762, pl ants infested at the 3-leaf stage produced more millable stal ks than untreated controls and plants infested at the 5and 7-leaf stages. Untreat ed controls in CP89-2143 produced more millable stalks than plants infested at all three leaf stages. Variety, leaf stage and variety leaf stage were significant in 2008, but variety leaf stage was not a significant source of variation in the model in 2009 for sugarcane yield (Table 4-3). Sugarcane yield in CP78 -1628 was significantly greater than in CP881762 and CP89-2143 in 2008 (Table 4-4), but in 2009 both CP78-1628 and CP88-1762 produced greater sugarcane yi eld than CP89-2143 (Table 45). Untreated control plants produced greater sugarcane yield than pl ants infested at all three leaf stages in 111

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both years. Plants infested at the 3and 5-leaf stages produc ed greater sugarcane yield than those infested at the 7-leaf stage. In variety leaf stage interactions, infestation at the 3and 5-leaf stages of CP78-1628 did not affect sugarcane yield compared to control, but infestation at the 7leaf resulted in significantly reduced yield. Although infestation at the 3-leaf stage in CP88-1762 result ed in more millable stalks produced than in the untreated c ontrol, the sugarcane yield was greater in the untreated control than in all the infested stages. In CP89-2143, plants in t he untreated control produced greater sugarcane yi eld than those infested at all the leaf stages. Variety, leaf stage and variety leaf stage we re significant sources of variation in 2008, but variety leaf stage was not signifi cant in the 2009 model for sucrose yield (Table 4-3). Although the sugarcane yield of CP88-1762 was lower than CP78-1628 in 2008, sucrose yields for the two varieties we re the same. Sucros e yield in CP78-1628 was significantly greater than CP89-2143 in 2008 (Table 4-4), but in 2009 both CP781628 and CP88-1762 produc ed greater sugarcane yield t han CP89-2143 (Table 4-5). Plants in the untreated control produced more sucrose than at all the infested stages. Infestation at the 3and 5-l eaf stages resulted in greater sucrose production than late infestation in both years. In the va riety leaf stage interactions, CP78-1628 had reduced sucrose yield only when in fested at the 7-leaf stage. Elasmopalpus lignosellus damage to CP88-1762 and CP89-2143 caused signifi cant sucrose yield losses at all the infested leaf stages compared to untreated controls. Percent reduction in sugarcane and sucrose yield in infested plants compared to untreated control plants in 2008 and 2009 ar e presented in Tables 4-5 and 4-6, respectively. Compared with untreated c ontrols, CP78-1628 had the least reduction in 112

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sugarcane (14% in 2008 and19% in 2009) and su crose yields (18% in 2008 and 19% in 2009), while CP89-2143 had the greatest reduction in sugarcane (34% in 2008 and 42% in 2009) and sucrose (30% in 2008 and 38% in 2009) yields. However, yield reduction does not provide details about pl ant compensation for early season lesser cornstalk borer damage. Percentage compensati on to initial damage was calculated by deducting percentage reduction in yield fr om damage percentage. The resulting compensation values were t hen compared among varieties in fested at different leaf stages. Variety (df = 2, 99, F = 1.81, P = 0.1686) was not signifi cant, but infested leaf stage (df = 3, 99, F = 33.18, P < 0.0001) and variety leaf stage (df = 6, 99, F = 3.89, P < 0.0001) were significant sources of variation in the model for percentage compensation in sugarcane yield in 2008. Similarly in 2009, vari ety (df = 2, 126, F = 1.95, P = 0.1469) was not significant, but leaf stage (df = 3, 126, F = 177.95, P < 0.0001) and variety leaf stage (df = 6, 126, F = 7.35, P < 0.0001) were significant sources of variation in the model for per centage compensation in sugarcane yield. Overall, no significant difference was detected among the tested varieties for compensation for lesser cornstalk borer da mage, but compensati on was greater when infested at 3followed by 5and 7-leaf stages in both years (T ables 4-6, 4-7). In variety leaf stage interaction, CP78-1628 and CP88-1762 compensated better than CP892143 for sugarcane yield at 3-leaf stage infest ation in 2009. However, sugarcane yield compensation following infestation at the 7-leaf stage was greater in CP89-2143 than in CP78-1628. For sucrose yiel d compensation following infest ation at the 7-leaf stage, CP89-2143 compensated better than CP78-1628 and CP88-1762 during both years. In 113

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CP78-1628 and CP88-1762, percentage compensation was signi ficant in the sequence of 3> 5> 7leaf stage. In CP89 -2143, percentage compensat ion in the plants infested at the 3and the 5leaf stage was same and it was greater than the plants infested at the 7leaf stage. Compensation in sucrose yield was sim ilar to sugarcane yield compensation. Again variety (df = 2, 99, F = 1.92, P = 0.1394) was not significant, but infested leaf stage (df = 3, 99, F = 39.25, P < 0.0001) and variety leaf stage (df = 6, 99, F = 4.16, P < 0.0001) were significant sources of va riation in the model for sucrose yield compensation in 2008. Similarly in 2009, variety (df = 2, 126, F = 0.84, P = 0.4251) was not significant, but l eaf stage (df = 3, 126, F = 192.14, P < 0.0001) and variety leaf stage (df = 6, 126, F = 6.12, P < 0.0001) were again significant sources of variation for sucrose yield compensation. Compensation in sucrose yield varied similarly among varieties and the infested leaf stages as compensation in sugarcane yield. Discussion Damage Results of this study showed that let hal damage (dead hearts or dead plants) and non-lethal damage (holes in leaves) by lesser cornstalk borer feeding varied with variety and time of infestation. Equal numbers of lesser cornstalk borer larvae produced the greatest lethal damage in CP89-2143 and n on-lethal damage in CP78-1628. CP892143 displayed greater susceptib ility to lesser cornstalk borer damage than the other two varieties. Damage differences am ong varieties may be due to morphological, physiological or biochemical resistance in plants. Agarwal (1969) reported that the physical and chemical make-up of sugarcane plants greatly influences their protection from insect damage. He reported that cell wall lig nification and the number of 114

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sclerenchymatous cell layers play an important role in imparting resistance against stem borers. Varietal differences in percent age lesser cornstalk borer damage were also reported by Chang and Ota ( 1989) with < 5% dead hearts in sugarcane varieties H836818 and H83-7498 compared to 23% dead hearts in H77-6359. Similar varietal differences were also reported for damage caused by other Pyralidae stem borers. Bessin et al. (1990) reported seasonal differ ences in injury by sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Pyralidae) among tested sugarcane clones that may have been due to resistance to stalk entry or antibiosis (larval survival). In another study, Pfannenstiel and Meagher (1991) r eported significant differences among sugarcane varieties to injury by the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Pyralidae). Infestation at the 3and 5leaf stages resulted in gr eater percentages of dead hearts and dead plants than when infested at the 7-leaf stage. Infestat ion at the 7-leaf stage resulted in a greater percentage of plant s with symmetrical rows of holes in the leaves. This may be due to increasing stem thickness with plant age that allowed fewer larvae to enter the stem to cause dead hear ts. This statement is supported by Rojanaridpiched et al. (1984) who found that silica and lignin contents of some maize varieties increases with age and are major factor s of resistance to stem borers at later plant development stages. Tiller Production Increased tiller production in plants infe sted at the 3-leaf stage in CP78-1628 and CP88-1762 may be the result of changes in growth regulat ing substances in damaged primary shoots (Dillewijn 1952). Changes in source-sink relationship due to damaged primary shoot may also be responsible for increased tiller production (Honkanen et al. 115

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1994). They reported that the damage to apical bud in P. sylvestris resulted in significant increase in mass and length of needles in lateral shoots. Lower tiller production in plants infested late rather t han early may be due to lesser cornstalk borer larval damage to both tillers and primary shoot s of the 7-leaf stage plants. In earlyinfested plants, only primary shoots were damaged because tillers had not yet developed. Larvae completed their developm ent by the time of tiller emergence in early-infested leaf stages and tillers esc aped from the damage. Tillers had already emerged by the time of the 7-leaf stage infestation and bot h primary shoots and tillers were available for borer damage. The lowe r tiller production in CP89-2143 than other two varieties was likely due to the greater percentage of dead plants that could not produce any tillers after damage. Compensation through increased tiller production in response to damage was also observed by Carbonell (1978), who reported t he recovery of lesser cornstalk borer damaged sugarcane plants through production of addi tional tillers. Similarly, Hall (1990) and Cherry and Stansly (2009) reported that early stand loss due to wireworm damage was compensated by increased tiller production during the sugarcane growing season. In rice, Rubia et al. (1996) reported that main stem injury due to Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) resulted in translocation of assimilates from the main stem to primary tillers, which might help in compensation for loss of the primary shoot. They also indicated that 33% dead hearts in 30 d old plants did not have a significant effect on productive tillers or grain yield. Jiang and Cheng (2003) reported that rice plants infested with striped stem borer, Chilo suppressalis (Walker) 116

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(Lepidoptera: Pyralidae) produced approximately one more tiller than untreated control plants 2 wk after infestation. Sugarcane Yield Traits Although the mean number of millable stalks produced in the untreated controls was less than in the plants infested at the 3and 5-leaf stages in CP78-1628, sugarcane and sucrose yield in th e untreated controls were the same as in the infested plants. Similarly, the number of millable stalks in plants infested at the 3-leaf stage in CP88-1762 was greater than or equivalent to plants in the untreated control, but sugarcane and sucrose yield were greater in the untreated controls than in all the infested leaf stages. The great er sugarcane yield in the un treated controls than in the infested leaf stages was due to greater millabl e stalk weight in the untreated controls, because sugarcane yield was a product of t he number of millable stalks and stalk weight in each bucket. This disparity in millable stalk weight among treatments was likely due to proportionately fewer primary shoots remaining and more tillers produced in early-infested than in untreated control pl ants at harvest. Early research by Stubbs (1900) and by Rodrigues (1928) determined a gradient in stalk weight and sugar content among shoots with primar y shoots having the greatest weight and richest juice (i.e., greater brix values) followed by secondary and then tertiary tillers. Compensatory response in sugarcane and sucrose yield in response to lesser cornstalk borer damage was dependent on infe sted leaf stage and va riety leaf stage interaction. The greater compensation in early damaged plants than late damaged plants may be due to more time available fo r early infested plants than late infested plants to compensate for the damage. Variations in sugarcane yield compensatory response with time of infestation were also reported by White and Richard (1985). They 117

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manually removed 25, 50 and 75% randomly selected sugarcane shoots (at 2-5 cm below soil level) in mid-March, mid-April, and mid-May to determine the effect of this shoot removal on sugarcane yield. They repor ted that the reductions in sugar yields tended to increase with the delay of shoot removal date during the crop season. Conclusions Lesser cornstalk borers ability to cause damage to sugarcane was dependent on variety and time of infestation. Equal numbe rs of lesser cornstalk borer larvae produced greater damage in CP89-2143 than in CP78-1628 and CP88-1762. Infestation of plants at the 3and 5-leaf stages produced more lethal damage (dead hearts + dead plants) than infestation at the 7-l eaf stage. Tiller production among varieties was dependent upon the level of damage: as damage increased, tillers production decreased. Tiller counts were greater in early damaged pl ants than late damaged plants, because E. lignosellus larvae damaged tillers in late-infested plants that were not present in earlyinfested plants. Millable stalk production was si milar to tiller production. Sugarcane and sucrose yield among varieties also varied according to the damage; more damage in CP89-2143 resulted in lower yield than the other two varieties. Early infestation resulted in more yield than late infestation in all the varieties. The compensation for damage was dependent on time of infestation and variety time of infestation. Comparison of sugarcane and sucrose yield r eduction with lethal damage shows that the varieties had equal ability to compens ate for lesser cornstalk borer damage. Compensation varied with the time of infest ation with greater co mpensation in earlyinfested than late-infested sugarcane. 118

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119 Future Directions The above conclusions were made based on the experiments conducted in the green house. In field conditions, many climat ic factors (sunlight, te mperature, moisture) and biological factors (insect population, other pests, natural enemies) can affect the results. This experiment could be conducted in the field to determine how season-long exposure to lesser cornstalk borers and population limiting factors (e.g., soil moisture and high summer soil surface temperatures) may affect damage throughout the season and resulting yields.

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120 Table 4-1. Analysis of variance of year, vari ety, leaf stage and their interactions on percentage E. lignosellus damage to sugarcane in 2008 and 2009 Dead hearts1 Holes in leaves2 Dead plants3 Total damage4 Source of variance df F P F P F P F P Block (B) 14 0.80 0.6494 0.62 0.8037 0.91 0.5465 0.45 0.9560 Variety (V) 2 3.52 0.0417 3. 51 0.0328 4.25 0.0189 3.93 0.0149 Leaf Stage (LS) 3 60.98 <0.0001 31.33 <0.0001 10.68 <0.0001 112.24 <0.0001 B V 28 0.61 0.9389 1.06 0. 5483 0.38 0.9428 1.52 0.0542 B LS 42 3.15 <0.0001 1.92 0.2795 0.81 0.6864 1.09 0.3772 V LS 6 4.74 0.0161 2.39 0.0312 2.44 0.0280 3.56 <0.0026 B V LS 84 0.92 0.6635 1. 00 0.4924 0.94 0.6136 0.92 0.6541 Error 300 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Necrosis of primary shoot and tillers and the cessation of further tiller production 4Summation of dead hearts, holes in leaves, and dead plants per bucket

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121 Table 4-2. Mean ( SEM) percentage E. lignosellus damage to sugarcane pooled across 2008 and 2009 Treatment variables Main effects Dead hearts1Holes in leaves2 Dead plants3 Total damage4 CP78-1628 48.3 2.1B 34.3 3. 1A 3.2 1.2B 85.8 2.4B CP88-1762 51.0 2.3AB 29.2 3.3AB 5.8 2.1B 86.0 2.7B Variety CP89-2143 55.7 2.5A 23.0 2.9B 16.0 3.4A 94.7 3.1A untreated 0d 0d 0c 0c 3-leaf 64.6 4.4a 14.2 2. 0c 11.3 2.2a 90.1 2.0a 5-leaf 54.9 3.1b 26.2 2.3b 9.7 1.9a 90.8 2.1a Leaf stage 7-leaf 35.5 2.2c 46.1 2.5a 3.9 0.6b 85.5 1.7b Interaction effects Variety Leaf stage Dead hearts Holes in leaves Dead plants Total damage untreated 0Ac 0Ac 0Ab 0Ac 3-leaf 63.1 8.9Aa 19.3 3.5A b 6.4 3.3Ba 88.8 4.0Aa 5-leaf 50.8 7.0Aa 33.8 4.5A ab 3.2 2.0Ba 87.8 5.1Aab CP78-1628 7-leaf 31.1 5.3Ab 49.8 5.9Aa 0Cb 80.9 3.2Ab untreated 0Ac 0Ad 0Ac 0Ab 3-leaf 67.8 7.7Aa 11.3 2. 5Bbc 8.0 3.2Ba 87.1 3.1Aa 5-leaf 51.3 7.1Aab 28.2 4. 6Ab 7.9 3.6Ba 87.4 2.6Aa CP88-1762 7-leaf 33.9 4.0Ab 48.1 6. 2Aa 1.4 0.3Bb 83.4 2.4Aa untreated 0Ac 0Ad 0Ac 0Ac 3-leaf 62.9 7.9Aa 12.0 .3 Ac 19.5 5.8Aa 94.4 4.5Aa 5-leaf 62.8 9.4Aa 16.5 .0 Bb 18.0 5.9Aab 97.3 5.7Aa CP89-2143 7-leaf 41.4 6.9 Ab 40.5 7.4 Aa 10.4 3.9 Ab 92.3 5.9Aa Means followed by different letters ar e significantly different (orthogonal contrasts, = 0.05) (SAS Institute 2008). Capi tal letters indicate contrasts among varieties (main effects) and am ong varieties at the same leaf stage (interaction effects). Small letters i ndicate contrasts among leaf stages (main effects) and among leaf stages in the same variety (interaction effects). 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Necrosis of both primary shoot and tille rs and the cessation of further tiller production 4Summation of dead hearts, holes in leaves, and dead plants per bucket

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122 Table 4-3. Analysis of variance effects on tillers, mill able stalks, sugarcane yiel d, and sucrose yield per bucket during 2008 and 2009 2008 Tillers1 Millable stalks2 Sugarcane yield3 Sucrose4 Source of variance df F P F P F P F P Block (B) 11 3.80 <0.0001 1. 35 0.2169 2.05 0.0352 2.13 0.0296 Variety (V) 2 19.90 <0.0001 8.29 0.0006 25.98 <0.0001 27.86 <0.0001 Leaf Stage (LS) 3 4.69 0.0032 4.78 0.0029 8.02 <0.0001 10.91 <0.0001 B V 22 6.58 <0.0001 1.70 0.0504 1.27 0.2135 1.34 0.1824 B LS 33 2.03 0.0011 1.87 0.1669 1.12 0.489 0.92 0.5928 V LS 6 6.00 <0.0001 3.77 0.0017 2.15 0.0684 1.95 0.0849 B V LS 66 4.13 <0.0001 1. 15 0.4216 1.18 0.3145 1.23 0.2325 Error 143 2009 Tillers Millable stalks Sugarcane yield Sucrose Source of variance df F P F P F P F P Block (B) 14 5.24 <0.0001 1.90 0.0376 5.29 <0.0001 6.15 <0.0001 Variety (V) 2 75.47 <0.0001 7.47 0.0010 83.08 <0.0001 95.90 <0.0001 Leaf Stage (LS) 3 28.41 <0.0001 15.36 <0.0001 123.66 <0.0001 122.26 <0.0001 B V 28 8.02 <0.0001 1.79 0.0219 5.93 <0.0001 6.23 <0.0001 B LS 42 0.68 0.9372 1.13 0.3180 1.02 0.4571 0.81 0.7658 V LS 6 10.77 <0.0001 3.22 0.0068 9.14 0.0004 13.69 <0.0001 B V LS 84 2.05 0.5245 1.69 0.1564 1.29 0.3416 2.45 0.2516 Error 179 1No. secondary and tertiary shoots 2No. stalks 1.5 m in height 3Total weight (Kg) of millable stalks in each bucket 4Raw sugar weight (Kg per bucket) ca lculated from brix and pol values

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Table 4-4. Mean ( SEM) tiller production and yield traits per bucket in 2008 Means followed by different letters are signi ficantly different (orthogonal contrasts, = 0.05) (SAS Institute). Capita l letters indicate contrasts among varieties (main effects) and among varieties at the same leaf stage (int eraction effects). Small letters indicate contrasts among leaf stages (main effects) and among leaf stages in the same variety (interaction effects). Treatment variables Main effects Tillers1 Millable stalks2 Sugarcane yield3 Sucrose yield4 CP78-1628 4.3 0.3A 3.6 0.2A 2.6 0.2A 0.26 0.02A CP88-1762 3.9 0.2A 3.2 0. 2A 2.1 0.2B 0.23 0.02AB Variety CP89-2143 3.1 0.2B 2.2 0. 1B 1.9 0.1B 0.21 0.02B untreated 3.8 0.2ab 3.0 0. 2ab 2.7 0.2a 0.28 0.02a 3-leaf 4.1 0.2a 3.2 0. 2a 2.3 0.1b 0.24 0.02b 5-leaf 3.8 0.2ab 3.0 0. 2ab 2.1 0.1b 0.23 0.02b Leaf stage 7-leaf 3.4 0.2b 2.8 0. 2b 1.7 0.1c 0.18 0.01c Interaction Variety Leaf stage Tillers Millable stalks Sugarcane yield Sucrose yield untreated 4.0 0.2Ab 3.3 0.2Ab 2.9 0.2Aa 0.3 0.02Aa 3-leaf 4.9 0.3Aa 3.9 0.2Aa 2.8 0.1Aa 0.28 0.02Aa 5-leaf 4.5 0.3Aab 3.8 0.3Aa 2.6 0.1Aa 0.27 0.02Aa CP78-1628 7-leaf 4.0 0.2Ab 3.3 0.2Ab 2.1 0.2Ab 0.19 0.01Ab untreated 3.7 0.2Abc 3.1 0. 1Ab 2.7 0.1Aa 0.28 0.03Aa 3-leaf 4.5 0.3Aa 3.6 0.2Aa 2.2 0.2Bb 0.24 0.02Bb 5-leaf 4.0 0.2Ab 3.2 0.2Ab 2.1 0.1Bb 0.23 0.02Bb CP88-1762 7-leaf 3.2 0.2Bc 3.0 0.1A b 1.7 0.2Ac 0.17 0.01Ac untreated 3.7 0.3Aa 2.8 0.2A a 2.6 0.2Aa 0.27 0.03Aa 3-leaf 3.0 0.3Bb 2.0 0.2B b 1.8 0.1Cb 0.20 0.02Cb CP89-2143 5-leaf 3.0 0.2Bb 2.1 0.1B b 1.7 0.1Cb 0.19 0.02Cb 7-leaf 2.9 0.2Bb 2.1 0.1Bb 1.5 0.1Ab 0.17 0.01Ab 1No. secondary and tertiary shoots 2No. stalks 1.5 m in height 3Total weight (Kg) of millable stalks in each bucket 4Raw sugar weight (Kg per bucket) ca lculated from brix and pol values 123

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Table 4-5. Mean ( SEM) tiller production and yield traits per bucket in 2009 Means followed by different letters are signi ficantly different (orthogonal contrasts, = 0.05) (SAS Institute). Capita l letters indicate contrasts among varieties (main effects) and among varieties at the same leaf stage (int eraction effects). Small letters indicate contrasts among leaf stages (main effects) and among leaf stages in the same variety (interaction effects). Treatment variables Main effects Tillers1 Millable stalks2Sugarcane yield3 Sucrose yield4 CP78-1628 5.4 0.3A 4.7 0.3A 3.1 0.2A 0.30 0.02A CP88-1762 5.2 0.3A 4.4 0. 2A 3.0 0.2A 0.28 0.02A Variety CP89-2143 3.5 0.2B 3.2 0. 2B 2.5 0.1B 0.22 0.02B untreated 4.6 0.2ab 4.3 0. 3ab 3.6 0.2a 0.33 0.02a 3-leaf 4.9 0.2a 4.4 0. 2a 2.9 0.1b 0.28 0.02b 5-leaf 4.7 0.2ab 4.2 0. 2ab 2.8 0.1b 0.26 0.02b Leaf stage 7-leaf 4.5 0.1b 3.8 0. 2b 2.0 0.1c 0.19 0.01c Interaction effects Variety Leaf stage Tillers Millable stalks Sugarcane yield Sucrose yield untreated 5.0 0.4Ab 4.4 0. 4Ab 3.7 0.3Aa 0.35 0.03Aa 3-leaf 6.0 0.4Aa 5.3 0.4Aa 3.6 0.2Aa 0.33 0.02Aa 5-leaf 5.5 0.3Aab 5.1 0.4Aa 3.3 0.2Aa 0.31 0.02Aa CP78-1628 7-leaf 5.1 0.3Ab 4.0 0.3Ab 2.0 0.1Ab 0.21 0.01Ab untreated 5.0 0.2Ab 4.3 0. 3Ab 3.6 0.3Aa 0.34 0.02Aa 3-leaf 5.6 0.3Aa 4.9 0.3Aa 3.1 0.2Bb 0.30 0.02Bb 5-leaf 5.1 0.2Aab 4.3 0.3Ab 2.9 0.1Bb 0.28 0.02Bb CP88-1762 7-leaf 4.9 0.2Ab 3.9 0.2A b 2.1 0.1Ac 0.19 0.01Ac untreated 4.4 0.3Aa 4.0 0.3A a 3.6 0.3Aa 0.31 0.03Aa 3-leaf 3.2 0.2Bb 2.8 0.2B b 2.2 0.2Cb 0.21 0.02Cb CP89-2143 5-leaf 3.4 0.2Bb 3.0 0.3B b 2.1 0.1Cb 0.19 0.01Cb 7-leaf 3.4 0.1Bb 3.0 0.2Bb 2.0 0.1Ab 0.18 0.01Ab 1No. secondary and tertiary shoots 2No. stalks 1.5 m in height 3Total weight (Kg) of millable stalks in each bucket 4Raw sugar weight (Kg per bucket) ca lculated from brix and pol values 124

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Table 4-6. Change in tiller production and yield traits in response to lethal damage (dead hearts + dead plants) caused by E. lignosellus in 2008. Percent change compared to control Main effects Damage1 (%) Tillers2 Stalks3Sugarcane yield4 Sucrose yield5 CP78-1628 51.5 + 10 + 11 14 (37.5A) 18 (33.5A) CP88-1762 56.8 + 05 + 05 28 (28.8A) 24 (32.8A) Variety CP89-2143 71.7 20 18 34 (37.7A) 30 (41.7A) 3-leaf 75.9 + 08 + 07 17 (58.9a) 14 (61.9a) 5-leaf 64.6 00 + 01 23 (41.6b) 18 (46.6b) Leaf stage 7-leaf 39.4 11 06 35 (04.4c) 36 (03.4c) Interaction effects Percent change compared to control Variety Leaf stage Damage (%) Tillers Stalks Sugarcane yield Sucrose yield 3-leaf 69.5 + 20 + 18 04 (65.5Aa) 07 (62.5Aa) 5-leaf 54.0 + 11 + 15 11 (43.0Ab) 10 (44.0Ab) CP78-1628 7-leaf 31.1 01 + 00 29 (02.1Ac) 37 (-6.1Bc) 3-leaf 75.8 + 22 + 17 19 (56.8Aa) 14 (61.8Aa) 5-leaf 59.2 + 07 + 02 27 (32.2Ab) 18 (41.2Ab) CP88-1762 7-leaf 35.3 14 03 37 (-1.7Ac) 39 (-4.3Bc) 3-leaf 82.4 20 21 28 (54.4Aa) 26 (56.4Aa) 5-leaf 80.8 19 17 34 (46.8Aa) 30 (50.8Aa) CP89-2143 7-leaf 51.8 22 17 41 (10.8Ab) 37 (14.8Ab) Values in parenthesis refe r to compensation percentage Means followed by different letters are significantly different (Tukeys, = 0.05) (SAS Institute 2008). Capital letters i ndicate contrasts among varieties (main effects) and among varieties at the same leaf stage (interaction effects). Small letters indicate contrasts among leaf stages (main effects) and among leaf stages in the same variety (interaction effects). 1Summation of percentage of pl ants with dead hearts and dead plants 2No. secondary and tertiary shoots 3No. stalks 1.5 m in height 4Total weight (Kg) of millable stalks in each bucket 5Raw sugar weight (Kg per bucket) ca lculated from brix and pol values 125

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Table 4-7. Change in tiller production and yield traits in response to lethal damage (dead hearts + dead plants) caused by E. lignosellus in 2009. Percent change compared to control Main effects Damage1 (%) Tillers2 Stalks3Sugarcane yield4 Sucrose yield5 CP78-1628 51.5 + 12 + 10 19 (32.5A) 19 (32.5A) CP88-1762 56.8 + 03 + 02 23 (33.8A) 26 (30.8A) Variety CP89-2143 71.7 22 27 42 (29.7A) 38 (33.7A) 3-leaf 75.9 + 07 + 02 19 (56.9a) 15 (60.9a) 5-leaf 64.6 + 02 02 22 (42.6b) 21 (43.6b) Leaf stages 7-leaf 39.4 12 14 45 (-6.4c) 42 (-2.6c) Interaction effects Percent change compared to control Variety Leaf stage Damage (%) Tillers Stalks Sugarcane yield Sucrose yield 3-leaf 69.5 + 21 + 21 03 (66.5Aa) 06 (63.5Aa) 5-leaf 54.0 + 11 + 17 09 (45.0Ab) 11 (43.0Ab) CP781628 7-leaf 31.1 + 03 09 44 (-12.9Bc) 40 (-8.9Bc) 3-leaf 75.8 + 11 + 14 14 (61.8Aa) 12 (63.8Aa) 5-leaf 59.2 + 01 + 00 16 (43.2Ab) 18 (41.2Ab) CP881762 7-leaf 35.3 02 09 40 (-4.7ABc) 44 (-8.7Bc) 3-leaf 82.4 17 31 39 (43.4Ba) 32 (50.4Aa) 5-leaf 80.8 12 26 42 (38.8Aa) 39 (41.8Aa) CP892143 7-leaf 51.8 13 26 46 (05.8Ab) 42 (09.8Ab) Values in parenthesis refe r to compensation percentage Means followed by different letters are significantly different (Tukeys, = 0.05) (SAS Institute). Capital letters indicate contrasts among variet ies (main effects) and among varieties at the same leaf stage (interaction effects). Small letters indicate contrasts among leaf stages (main effects) and among leaf stages in the same variety (interaction effects). 1Summation of percentage of pl ants with dead hearts and dead plants 2No. secondary and tertiary shoots 3No. stalks 1.5 m in height 4Total weight (Kg) of millable stalks in each bucket 5Raw sugar weight (Kg per bucket) ca lculated from brix and pol values 126

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Figure 4-1. Lesser cornstalk borer damage in sugarcane: A) Larva coming out of silken tunnel, B) Larval entry site in the plan t, C) Dead heart, D) Holes in the leaves. 127

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CHAPTER 5 EFFECTS OF HARVEST RESIDUE AND TILLAGE LEVEL ON ELASMOPALPUS LIGNOSELLUS DAMAGE TO SUGARCANE Introduction Lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) is a pest of many crops, including sugarc ane (Falloon 1974). Sugarcane is produced vegetatively from mature stalks with new plants formed from shoots emerging from growth points above each node ( Dillewijn 1952). Larval feedi ng on sugarcane primary, secondary and tertiary shoots results in dead heart symptoms and dead plants that can translate into reduced sugarcane and sugar yield at harvest (Sandhu et al. 2010b). Sugarcane is harvested annually in souther n Florida, with ratoon crops usually produced for several years following the firs t harvest (Baucum an d Rice 2009). This habitat provides a year-round food source and reservoir for lesser cornstalk borer from which to renew its attack on the sensitive crop following each harvest and to move out to surrounding crop hosts, such as corn and peanuts. Chemical insecticides have been tested for many years to control lesser cornstalk borer with varying success (Arthur and Arant 1956, Reynold et al. 1959, Harding 1960, Chalfant 1975, Hyche et al. 1984, Mack et al. 1989, Mack et al. 1991, Chapin and Thomas 1998). Many of the su ccessful materials are no longer labeled for use on these or any other crops. Most re cently, the United States Environmental Protection Agency revoked tolerances for carbofuran which was labeled for multiple insect control in sugarcane, effectively removing the last of the effective products for controlling lesser cornstalk borer larvae protect ed within plants (EPA 2009). M any authors have come to the conclusion that the lesser cornstalk borer is difficult to control with insecticides (Arthur and Arant 1956, Reynol d et al. 1959, Harding 1960, and Chalfant 1975), but 128

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chemical insecticides remain important for its control in some crops, such as peanuts (Chapin and Thomas 1998). Natural control of E. lignosellus is poorly understood in southern Florida. Falloon (1974) claimed that low levels of predation and parasitism in sugarcane in Jamaica were a result of larvae protected in the soil by the silken tunnels, and due to destruction of the natural enem y complex by pre-harvest burning. Cultural practices were reported to be effici ent in lesser cornstalk borer in different crops. For fall beans, Isley and Miner ( 1944) recommended inspecting crop residues before planting to determine whether a thoro ugh soil preparation was necessary to kill half-grown larvae. They believed that larv ae from eggs deposited after planting would not have enough time to develop to destructive size before the plants passed the most susceptible stage of growth. Cowan and Dempsey (1949) observed a reduction in lesser cornstalk borer damage to pimiento pl ants in thoroughly cultivated land compared to conservation tillage before planting. Dupr ee (1964) reported that land kept fallow for 8-10 wk before planting resulted in a significant reduction of borer damage to peanuts and soybean. In Hawaii, Smith and Ota (2 002) reported that prompt irrigation application at the appearanc e of adults in the field was t he most efficient practice to control lesser cornstalk borer in sugarcane. Sugarcane can be harvested following a pr e-harvest burn or harvested green without burning (i.e., green harvesting). Green harvesting leav es a blanket of leaf and stalk residues (i.e., trash blanket) on the soil surface after harvesting while pre-harvest burning results in the soil being mostly ex posed following harvest. Lesser cornstalk borer outbreaks in sugarcane are frequently associated with either the pre-harvest burning of sugarcane to remove leaf material from the harvest st ream, or with post129

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harvest burning of the trash left on the so il surface to improve fertilizer penetration and water percolation into the soil (Plank 1928, Wolcott 1948, Bennett 1962, Metcalfe 1966). Release of smoke during s ugarcane burning was reported to attract lesser cornstalk borer adults towards the burning field (B ennett 1962). Leuck (196 6) observed that female E. lignosellus prefer to deposit eggs in the soil. High soil moisture has previously been associated with high larv al mortality (Knutson 1976) and low egg deposition (Mack and Backman 1984). Therefore, oviposition and larval survival may be hindered by a trash blanket covering the soil surface. However, production of a trash blanket may result in other agronomic problems for sugarcane. Retention of sugarcane trash interferes with fertilizer and herbicide applications, water percolation, and can immobilize N and P (Ng Kee Kwong et al. 1987). Soil incorporation of sugarcane trash has been found to increase decomposition rates and increase yield (Kennedy and Arceneaux 2006). Tillage with discs (disking) can be used to incorporate sugarcane trash into the soil, but this can result in re-exposure of the soil surface, thereby increasing the favorability for lesser cornstalk borer egg deposition. In sugarcane, lesser cornstalk borer preferabl y deposits eggs near the plant base (Smith and Ota 2002); therefore, it is possible that egg deposition may be reduced by retaining a trash blanket around the plant bases. The remaining trash could be disked into the soil potentially eliminating grower conc erns for fertilizer application and water percolation problems associ ated with trash blankets. Due to growing worldwide interest in reducing environmental pollution, the practice of pre-harvest burning of sugarcane has become either ill egal or highly regulated. Additionally, with few insecticides currently available for controlling E. lignosellus in 130

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sugarcane, alternative strategi es are needed to control this insect. Therefore, trash blankets could play an im portant future role in the interaction of lesser cornstalk borer and sugarcane. The first objective of this study was to compare the effects of trash blankets on lesser cornstalk borer damage and yield in plant cane versus ratoon sugarcane fields. The second objective was designed to address grower concerns of reduced water percolation and fertilization penetrati on associated with trash blankets by comparing the combined effects of har vest method (green cane and burnt cane harvesting) and tillage levels (no-tillage, intermediate, and conventional tillage) on lesser cornstalk borer damage and yield. Materials and Methods Experimental Design The first study was conducted at Graham Da iry farm, Moore Haven, Florida, to evaluate the effect of harvest residue (tra sh or no-trash) on lesser cornstalk borer damage and sugarcane yield in plant cane and ratoon fields. The farm location was selected based on grower complaints of annual excessive sugarcane stand loss to lesser cornstalk borer. Plant cane and ratoon fields of sugarcane variety CP89-2143, widely grown on sandy soil (Rice et al. 2009), we re selected for the trial. The farm was located in northeastern Hendry County, Flor ida comprised of mostly Immokalee fine sand soil. A first ratoon crop was green harvested in April 2006, leaving a 15-20 cm deep trash blanket on the soil surface. Approx imately one week earlier in a neighboring field, CP89-2143 stalks harvested from within the same farm were planted to produce the plant cane field. An experiment was des igned with a split plot design with plant and ratoon sugarcane fields as the main plots and plots with and without trash blankets as the subplots. Main plots 21.5 m long and 4 rows (6 m) wide were marked off within 131

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each field at least 25 m from fi eld edges and separated from other main plots by > 33 m. Two subplots 10 m long by 4 rows wide (6 m) were established within each main plot separated by 1.5 m along the row axes. The trash blanket was manually removed from one of the subplots in each main plot to produce trash and no-trash subplots in the ratoon sugarcane field. The har vest trash removed from t he ratoon sugarcane field was collected in trucks and distributed onto the tras h subplots in the plant sugarcane field. Trash removed from one subplot in the rato on sugarcane field was used to cover one subplot in the plant sugarcane field. Pair ed subplots were replicated six times in the ratoon and plant sugarcane fields. Weed control and fertilization were applied as needed to local standards. No insecticides or fungicides were applied to either plant or ratoon sugarcane field. The effects of harvesting method (green harvest versus pre-harvest burning) combined with tillage level on damage caused by lesser cornstalk borer and sugarcane yield were evaluated in two separate field studies during 2008 (March to November) and 2009 (March 2009 to January 2010). Studies were conducted at different field locations of the same sugarcane farm located near Clewis ton, Florida. Fields planted to variety CP78-1628, also widely grown on sandy soils (Rice et al. 2009), were selected in both years. The sugarcane fields were in t heir second ratoon in 2008 and first ratoon in 2009. The experimental design was again a sp lit plot design with harvesting method as the main plots and tillage level as subplots. Main plots we re established in neighboring fields by applying pre-harvest burning to one field and harvesting the adjacent field green. Green cane harvesting left a 10-15 cm deep trash blanket on the soil surface during both years. There was minimal plant residue following harvest in the fields with 132

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pre-harvest burning in both years. Three tillage levels were applied randomly in vertical strips (8 rows wide each) adjacent to each other along the entire field in each main plot. Out of eight rows with each tillage treatment sample subplots 10 m long were selected from only the central four rows (6 m wide) with the two remaining rows on either side used as buffers. Therefore, main plots with harvesting method were 10 m long and 24 rows (36 m) wide, and subplots with each tillage level were 10 m long and 4 rows (6 m) wide with 4 rows separation between subplots within the same main plot. Main plots were separated from each other by 45 m. Main plots were replicated 6x in 2008 and 12x in 2009 in each harvesting method field. Trials were begun in March 2008 and March 2009. To establish no-tillage subplots, soil was left undisturbed or uncultivated following harvest in both green cane and burnt cane harve sted plots. To es tablish conventional tillage plots, a single disking was performed 2 wk after harvest of the previous seasons crop. A 5-m wide commercial disc cultivator was used to cultivate soil after harvesting. Discs were arranged on 2 tool bars (front and rear rows) and were used to cultivate 4 rows on each pass through the field. In t he conventional tillage treatment, the combined front and rear rows of discs resulted in cultivated lines evenly distributed between planted rows with a minimum of 6-8 cm dist ance from the planted row centers. To establish plots with intermedi ate tillage, discs were manually adjusted towards the row middles to increase the distance fr om the planted row centers to 15 cm. No insecticide or fungicide was applied to plant or ratoon cane fields in 2008 or 2009. Weed control and fertilization were applied as needed to local standards. 133

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Damage Assessment In all these experiments, feeding damage was recorded for primary shoots and tillers (secondary or tertiary shoots) in random ly selected 3-m sections of row in each of the 4 rows of each subplot. The num ber of dead hearts, num ber of plants with symmetrical rows of holes in leaves, and number of plants dama ged by other foliar feeders (e.g. grasshopper, armyworms) were recorded biweekly beginning 3 wk after plant emergence in each treatment. Damage was recorded for the first 3 mo of growth period, which was reported to be the critical exposure peri od for lesser cornstalk borer damage to sugarcane (Carbonell 1978) Plants were counted as dead hearts if lesser cornstalk borer feeding lead to chlorosis and necrosis of only the primary shoot. Plants were also counted that displayed symmetrical rows of holes in leaves following nonlethal feeding by lesser cornstal k borer to a few superficial layers of sugarcane shoot. Plants with leaves notched by foliage feeder pests (e.g., grasshoppers and armyworms) were counted as damage by other pests. Plant s were first observed for dead hearts, then holes in the leaves, and then damage by other pests. Plants counted as dead hearts could not be counted as holes in leaves, and plants with holes in leaves could not be counted for damage by other pests Lesser cornstalk borer damage was confirmed by observing randomly selected damaged plants for the presence of subsoil surface silken tunnels attached to the point of larval entry to the plant. The mean percentage of plants with dead he arts, holes in the leaves, and damaged by other pests were calculated using the observations on all damaged and undamaged plants per 3 m row section at the time of maximum damage. Total damage by lesser cornstalk borer was calculated as the summation of dead hearts and plants with holes in the leaves per 3 m row section. 134

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Sugarcane Yield Assessment Millable stalks (primary shoots and tillers > 1.5 m height) from all the rows in each plot were counted 8 mo. after the first emer gence of sugarcane shoots in all the trials. Millable stalks were counted in the 8 mo. ol d crop, because lodging in sugarcane at harvest time interferes with determining the height and exact number of millable stalks. Randomly selected stalks greater then 1.5 m in height were cut for yield determination by hand using cane knives at < 20 cm above the soil surface and then weighed using a truck-mounted sling scale. Ten stalks from each of the 4 rows of each subplot (total 40 stalks) were harvested in 2006 and 2008. Ten st alks from the middle two rows (total 20 stalks) were harvested in 2009. Plant fresh weights were used to determine individual stalk weight (Kg per stalk), and biomass yi eld as tons of cane per acre (TCA) was calculated as the product of stalk number and stalk wei ght. To determine sucrose concentration, 10 stalks (randomly selected fr om harvested stalks of each plot) were milled and the crusher juice analyzed for brix and pol as described by Gilbert et al. (2008). Sugar yield as tons of sugar per ac re (TSA) was calculated according to the theoretical recoverable sugar method (Glaz et al. 2002). Data Analysis PROC MIXED (SAS Institute 2008) with the repeated measures statement was used to analyze the damage data due to potentia l covariance structure associated with repeated damage assessments over time in the same locations. Dates were used as the repeated variable in the repeated measur es statement. Several covariance structures were fitted to the data. T he unstructured covariance type fit well and was used for the analysis (Littell et al. 1998). Percentage data were arcsin transformed before analysis and retransformed for presentation purposes. Data on yield traits were 135

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analyzed using PROC GLM procedure for a split plot design (SAS Institute 2008). The Tukeys HSD test (SAS Institute 2008) was used for means separation with = 0.05. Results Results of the 2006 study on the effects of crop age and trash blankets (Tables 51 to 5-3) are presented separately from the 2008 and 2009 studies on the effects of harvesting method and tillage (Tables 5-4 to 5-9). Dead hearts were the most commonly observed result of E. lignosellus feeding damage to sugarcane in both studies. Symmetrical rows of holes in leav es were the second (aft er dead hearts) most commonly observed damage in both studies The sum of plant feeding damage caused by E. lignosellus (dead hearts, holes in leaves) was analyzed as total damage in both studies. Effects of Crop Age and Trash Blanket Crop age significantly affected lesser corn stalk borer damaged plants with holes in leaves and total damage (Table 5-1). Ha rvest residue and harvest residue crop age were significant sources of variation in the model for dead hearts and total damage. Plant cane had significantly greater percentage of plants with dead hearts, holes in leaves and total damage than ratoon cane (Tabl e 5-2). Overall, plots with trash blankets had significantly reduced mean perc entage of plants with dead hearts, holes in leaves and total damage. However, separati on of the means by interaction with the crop age determined that the pres ence of a trash blanket signi ficantly affected lesser corn stalk borer damage only in the plant cane field. There were significantly greater percentages of plants with dead h earts, rows of holes in leaves, and total damage in plant cane plots without trash than in the ratoon field plots without trash. There was a significantly greater percentage of plants with rows of holes in the plant cane plots with 136

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trash than the ratoon cane field with trash. Total damage was > 3x greater in the plant cane field plots without a trash blanket compared to plots with a trash blanket. Damage by other foliar feeders was < 3% in both plant and ratoon cane fields. Crop age was significant, but harvest residue and their interaction were not significant sources of interaction in the model for dam age by other pests (Table 5-1). Plant cane had significantly greater perc entage of shoots damaged by other pests than ratoon cane (Table 5-2). Trash blanket did not have a si gnificant effect on damage by other pests either in plant cane or in ratoon cane. There was significantly greater percentage of plants damaged by other pests in plant cane with trash than ratoon cane with trash. Crop age was a significant source of variat ion in the model for millable stalks per row and mean stalk weight (Tabl e 5-1). Neither the harvest residue nor the interaction of crop age with harvest residue had significant effects on these two yield parameters. The mean number of millable stalks was greater in ratoon cane than plant cane, but mean stalk weight was greater in plant cane than ratoon cane (Table 5-3). The trash blanket did not have a significant effect on the mean number of m illable stalks per row or stalk weight. Ratoon cane with trash pr oduced greater number of millable stalks than plant cane with trash, and ratoon cane without trash produced greater number of millable stalks than plant cane without trash. However, the reverse was true for stalk weight with plant cane plots with and without trash having gr eater stalk weight than ratoon cane plots with and withou t trash, respectively. Neither TCA nor TSA were affected by crop age, harvest residue or their interaction (Table 5-1). The mean TCA and T SA were equivalent in plant and ratoon cane, and with trash or without trash blankets. 137

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Effects of Harvesting Method and Tillage In this second study, the experiment year (df = 1, 431) was a significant source of variation in the model for dead hearts ( F = 123.54, P < 0.0001), holes in leaves ( F = 253.96, P < 0.0001), total damage (F = 16.97, P < 0.0001) and damage by other pests ( F = 551.33, P < 0.0001). Therefore, the data were analyzed and presented separately for 2008 and 2009 (Table 5-4). Harvesting method, tillage level, and their in teraction were significant sources of variation in the model for dead hearts, holes in leaves and total damage caused by lesser cornstalk borer in sugarcane during both years (Table 5-4). Plots in the field with pre-harvest burning had significantly great er percentages of plants with dead hearts, plants with holes in leaves, and total damage than in plots in the green harvested field in both years (Tables 5-5 and 56). Percentage of plants with dead hearts and the total percentage of damaged plants were > 3x greater in the field bur ned prior to harvest than in the green harvested field in both years. Subplots with conv entional tillage had significantly greater percentage of plants wit h dead hearts, holes in the leaves and total damage than the subplots with no-t illage or intermediate tillage. Lesser cornstalk borer caused approximately 1.5x gr eater damage in subplots with conventional tillage than subplots with no-tillage and inte rmediate tillage. However, tillage levels significantly affected lesser cornstalk borer damage in green cane harvested plots only, where again subplots with conventional tillage had great er percentages of plants with dead hearts, holes in leaves, and total damage than the subplots with no-tillage and intermediate tillage. Percentage of plants with dead hearts in subplots with conventional tillage (20.4 0.9%) was > 21x greater than in subplots with no-tillage (0.93 0.2%), and > 13x greater than subplots with inte rmediate tillage (1.5 0.3%). Similarly, percentage of 138

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total damage in conventional tillage subplot s was >13x greater than in no-tillage and intermediate tillage subplots. Neither main effects nor their interaction we re significant sources of variation in the model for damage by other pests in 2008, but harvesting method was significant in 2009 (Table 5-4). Plots in the green harvested field had a greater percentage of plants damaged by other pests than burnt cane harvest ing in 2009 (Table 5-6). Tillage level did not produce any significant effect on damage by other pests in main effects or in interaction with harvesting method duri ng both years (Tables 5-5 and 5-6). Experiment year (df = 1, 287) was also a significant source of variation in the models for mean number of millable stalks ( F = 104.84, P < 0.0001), mean stalk weight ( F = 46.11, P < 0.0001), mean TCA ( F = 142.61, P < 0.0001), and mean TSA ( F = 90.34, P < 0.0001); therefore, the data were analyzed s eparately for 2008 and 2009 (Table 5-7). The significant year effect resu lted from greater yield traits in 2009 than in 2008 (Tables 5-8 and 5-9). Neither main effects nor their interaction we re significant sources of variation in the model for millable stalks in 2008, but harve sting method was significant in 2009 (Table 5-7). In 2009, the mean number of millable stalks in burnt cane harvested plots (173.8 3.4) was significantly greater than in green cane harvest ed plots (163.1 3.3) (Table 5-9). In harvesting method tillage level in teraction, subplots with no-tillage in green cane harvested plots had significantly greater number of millable stalks than same tillage level in burnt cane harvested plots in 2008 (Table 5-8). Sim ilarly, the subplots with intermediate tillage in green cane harvested plot s produced more number of millable stalks than same tillage level in burnt cane harvested plots in 2008. In green 139

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cane harvested plots, the subplots with interm ediate tillage produced greater number of millable stalks than subplots with conventional tillage. In 2009, subplots with no-tillage, conventional and intermediate tillage levels in burnt cane harvested plots produced greater number of mill able stalks than the subplots with res pective tillage levels in green cane harvested plots (Table 5-9). Harvesting method and harvest method tillage level were significant sources of variation in the model for stalk weight in 2008, and harvesting method and tillage level were significant in 2009 (Table 5-7). Green cane harvested plots had greater stalk weight than burnt cane harvest ed plots during both years (Tab le 5-8 and 5-9). Tillage levels did not affect stalk weight in 2008, but the subplots with intermediate tillage (0.72 0.03) and conventional tillage (0.70 0.02) had greater stalk weig ht than subplots with no-tillage (0.65 0.02) in 2009 (Table 5-9). In harvesting method tillage level, subplots with no-tillage in green cane harve sted plots had greater stalk weight than subplots with same tillage in burnt cane harvested plots during both y ears. Similarly, intermediate tillage subplots in green cane ha rvested plots produced heavier stalks than the same tillage level subplots in burnt cane harvested plots during both years. In green cane harvested plots, the stalk weight was greater in subplots with intermediate tillage than subplots with no-tillage and conventional tillage during both years. However in burnt cane harvested plots, conventional tillage subplot s produced heavier stalks than no-tillage subplots during both years. Harvesting method and harvesting method tillage level were significant sources of variation in the model for TCA in 2008 (Table 5-7). In 2009, harvesting method was not significant source of variation in the model, but tillage level and harvesting method 140

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tillage level were significant for TCA. Green cane harvested plot s (33.2 0.6) produced greater TCA than burnt cane harvested plots (30.2 0.5) in 2008, buy there was no difference in 2009 (Table 5-8 and 5-9). TCA wa s not affected by tillage levels in 2008, but the subplots with conventional tillage (37. 8 1.3) and intermediate tillage (38.2 1.3) had greater TCA than subpl ots with no-tillage (34.9 1. 2) in 2009 (Table 9). In harvesting method tillage level, subplots with intermediate tillage (35.1 0.6) had greater TCA than subplots with c onventional tillage (31.3 0.7) in green cane harvested plots in 2008. In 2009, subplots with interm ediate tillage (40.1 1.4) had greater TCA than subplots with no-tillage (36. 1 1.3) in green cane harvested plots. In burnt cane harvested plots, subplots with conventional tillage (32.0 0.7) had greater TCA than subplots with no-tillage (28.7 0.6) and interm ediate tillage (29.8 0. 6) in 2008, but the difference between conventional tillage and inte rmediate tillage was not significant in 2009. Only the interaction of harvesting method tillage level had a significant affect on the model for TSA during both years (Table 5-7) In harvesting method tillage level, subplots with intermediate tillage (5.50 0.19) had greater TSA than subplots with notillage (5.10 0.18) in 2009 only (Table 5-9) In burnt cane harve sted plots, subplots with conventional tillage produced more T SA than subplots with no-tillage during both years. The subplots with in termediate tillage in green cane harvested plots had greater TSA than subplots with intermediate tillage in burnt cane harvested plots in 2009. Discussion Effects of Crop Age and Trash Blanket This study shows that trash blanket signi ficantly reduced the le sser cornstalk borer damage to sugarcane plants. The presence of a trash blanket resulted in a reduction in 141

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percentage of plants with dead he arts by approximately 11x in plant cane and 2x in ratoon cane plots. Hall (1999) also reported that only 0.5% shoots were killed by lesser cornstalk borer in the field with trash blanket compared to 7.0% shoots killed in fields without trash blankets. This reduction in lesser cornstalk borer damage might be due to inhibition of egg deposition by the trash blanket (Leuck 1966). The other probable reason for less damage in plots with trash wa s that trash blanket s maintained higher moisture levels than exposed soil, which ei ther inhibited egg deposition or increased larval mortality. Leuck (1966) reported inhibition of egg deposition by soil moisture. Knutson (1976) reported greater larval mo rtality when reared in soil with 100% water holding capacity than in dry soil. The damag e by other foliage feeder pests remained low in all the plots and was not affected by the presence of a trash blanket. Although the mean damage percent age was significantly greater in plots with trash than plots without trash, the ef fects of a trash blanket on m illable stalks, stalk weight, TCA, and TSA were not significant. This lack of significant difference between the main treatments may be due to recovery of so me damaged plants to normal growth or compensation of early season lesser corn stalk borer damage by production of additional tillers in the damaged plants. Carbonell (1978) reported 27.8% recovery in plant canes and 48.1% recovery in ratoon canes in respons e to lesser cornstalk borer damage. The compensatory response of CP89-2143 was also reported by Sandhu et al. (2010b). They reported that this variety can com pensate for up to 37.7% of dead hearts and dead plants caused by lesser cornstalk borer without significant reduction in sugarcane yield. 142

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Effects of Harvesting Method and Tillage This study shows that the effect of tillage level on lesser cornstalk borer damage was dependent on harvesting method. Tillage le vel provided significant effects in green cane harvested plots only, in which subpl ots with conventional tillage had 13-21x greater percentage of plants with dead hear ts than subplots with no-tillage and intermediate tillage. In conventional tillage su bplots, the soil was cultivated very close (6-8 cm from row center) to the plant bas e thereby exposing the soil surface near the plant base while incorporating the trash into the soil. Lesser cornstalk borer deposits most of the eggs on soil surface near the plant base (Smith and Ota 2002), which was exposed in conventional tillage and cover ed with trash in no-tillage and intermediate tillage. In intermediate tillage, only the in ter-row space was cultivated leaving the trash adjacent to the plant bases undisturbed, wh ich may have inhibited lesser cornstalk borer egg deposition. T he harvest residue trash blanket near the plant base also may provide a food source for lesser cornstalk borer larvae in no-tillage and intermediate tillage subplots thereby reducing the overa ll damage to sugarcane plants. This idea is supported by Cheshire and All (1979) who c onducted greenhouse simulations of a corn cropping system using mulched no-tillage, mulched conventional tillage, and conventional tillage. They reported different lesser cornstalk borer larvae behavior on corn in no-tillage than in conventio nal tillage cultural practices. In 20 replicates of 2 corn plants per replicate, the number of attacked plants was only 4 in no-tillage with wheat and rye residues mulch compared to 22 in conventional tillage. They concluded that mulched residues in the no-tillage treatment pr ovided an alternate food source resulting in reduced damage to the corn. 143

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Yield differences between treatment year s are probably attributable to a longer crop cycle in 2009 (10 mo) than 2008 (8 mo). In 2008, greater lesser cornstalk borer damage to sugarcane resulted in fewer milla ble stalks and lower TCA in conventional than intermediate tillage in the green harvested field. Fe eding damage was not fully compensated for during the sugarcane growth cycle and resulted in yield loss. However, the same pattern of greater damage to plants in conventional than intermediate tillage plots in 2009 did not result in fewer millable stalks and lower TCA in conventional than intermediate tillage. Thes e results suggest that the sugarcane plants had enough time to fully compensated fo r the damage in 2009 compared to 2008. Dillewijn (1952) also reported that plant compensation capability increased with longer sugarcane growth seasons. Differences in TCA and TSA between seasons and tillage levels may be the result of differences in compensation time and me chanical damage to sugarcane stools. The reduction in TCA and TSA in the no-tillage compared to other tillage subplots in the green harvested field in 2009 may have been due to excessive soil moisture or lower soil temperature under the trash blanket. Excessive soil wetness and lower soil temperature in green harvested fields were reported to reduce sugarcane biomass and sugar yields compared to pre-harvest burned fields (Oliviera et al. 2001). In the preharvest burned field, lesser cornstalk borer damage was the same for all tillage levels, but TCA and TSA were greatest in the conv entional tillage subplots. The conventional tillage treatment likely caused more damage to the first shoots growing from the stools following harvest than in the intermediate and no-tillage subplots. Mechanical damage to these first shoots may have resulted in greater numbers of millable stalks and 144

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145 elevated yields compared to other tillage leve ls. It is a common grower practice in southern Florida sugarcane to cultivate close to planted rows or to use tines to scratch over planted rows with the idea that this increases tillering and yield. Conclusion Overall, we can conclude that lesser co rnstalk borer damage can be reduced by harvesting the sugarcane green or through application of harvest residue to cover the soil surface around sugarcane pl ants. Intermediate tillage allowed for greater rain percolation and fertilizer penetration while maintaining low levels of lesser cornstalk borer damage. In burnt cane harvested plot s, all tillage levels had equal lesser cornstalk borer damage, but c onventional tillage resulted in increased TCA and TSA. Although the sugarcane plant s compensated for lesser co rnstalk borer damage in our 2006 and 2009 studies, severe outbreaks of this pest can result in significant yield reduction.

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146 Table 5-1. Analysis of variance of crop age, harvest residue and their interaction on E. lignosellus and other pests damage to sugarcane, and sugarcane yield traits in 2006 Source of variation Dead hearts1 Holes in leaves2Total damage3 Other pests4 df F P F P F P F P Crop age (CS) 1 0.81 0.4096 36.17 0.0018 21. 89 0.0054 9.90 0.0255 Harvest residue (HR) 1 45.14 0.0011 5.79 0.0611 16.71 0.0095 0.29 0.6150 HR SC 1 18.33 0.0079 3.14 0. 1367 7.52 0.0407 0.27 0.6244 Error 95 Source of variation Millable stalks5 Stalk weight6 TCA7 TSA8 df F P F P F P F P Crop age (CS) 1 14.29 0.0129 22.33 0.0052 0. 60 0.4719 1.31 0.3040 Harvest residue (HR) 1 1.73 0.2449 0.26 0.6292 0.00 0.9973 0.00 0.9605 CS HR 1 4.77 0.0806 0.99 0. 3655 0.01 0.9287 0.03 0.8706 Error 95 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Summation of dead hearts and holes in leaves 4Primary shoots and tiller s with leaves damaged by other fo liage feeders (e.g. grasshoppers, armyworms) 5No. stalks 1.5 m in height 6Weight (Kg) of individual millable stalk 7Sugarcane biomass yield in metric tons of cane per acre (TCA) 8Raw sugar weight in metric tons of sugar per acre (TSA), calculated from brix and pol values

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Table 5-2. Mean ( SEM) percentage of E. lignosellus and other pests damage to sugarcane in 2006 Treatment variables Main effects Dead hearts1Holes in leaves2 Total damage3 Other pests4 Crop age Plant cane 4.3 0.7A 6. 2 0.4A 10.4 0.9A 2.4 0.6A Ratoon cane 2.4 0.4B 0.6 0.2B 02.9 0.3B 0.3 0.1B Trash 1.2 0.2b 2.1 0.4b 03.2 0.3b 1.6 0.4a Harvest residue No-trash 5.5 0.8a 4.6 0.7a 10.1 1.1a 1.1 0.3a Interaction effects Crop age Harvest residue Dead hearts Holes in leaves Total damage Other pests Plant cane Trash 0.7 0.3Ab 3.7 0.8Ab 04.4 0.8Ab 2.9 0.8Aa No-trash 7.8 1.6Aa 8.6 1.4Aa 16.4 2.3Aa 1.9 0.7Aa Ratoon cane Trash 1.6 0.4Aa 0.5 0.3Ba 02.0 0.4Aa 0.3 0.1Ba No-trash 3.1 0.7Ba 0.6 0.2Ba 03.7 0.7Ba 0.3 0.2Aa Means followed by different letters are significantly different (Tukey, = 0.05) (SAS Institute 2008). Capital letters indicate differences between crop ages (main effects) and between crop ages at the same harvest resi due (interaction effects). Small letters indicate differences between harvest resi dues (main effects) and between harvest residues at the same crop age (interaction effects). 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Summation of dead hearts and holes in leaves 4Primary shoots and tillers with leaves damaged by other foliage feeders (e.g. grasshoppers, armyworms) 147

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148 Table 5-3. Mean ( SEM) yield traits in cr op age, harvest residue, and their interactions in 2006 Treatment variables Main effects Millable stalks1Stalk weight2TCA3 TSA4 Crop age Plant cane 155.2 2.3B 1.36 0.04A 67.8 1.9A 10.0 0.4A Ratoon cane 176.1 2.4A 1.15 0.03B 64.4 1.8A 09.3 0.3A Trash 167.7 2.6a 1.24 0.03a 66.1 2.1a 09.6 0.4a Harvest residue No-trash 163.5 2.7a 1.27 0. 04a 66.1 1.9a 09.7 0.3a Interaction effects Crop age Harvest residue Millable stalks Stalk weight TCA TSA Plant cane Trash 154.4 4.1Ba 1.37 0.05Aa 67.9 3.7Aa 09.9 0.6Aa No-trash 155.9 4.2Ba 1.35 0.05Aa 67.6 3.6Aa 10.1 0.6Aa Ratoon cane Trash 181.0 4.6Aa 1.11 0.04Ba 64.2 3.5Aa 09.3 0.6Aa No-trash 171.1 4.4Aa 1.18 0.04Ba 64.5 3.5Aa 09.2 0.6Aa Means followed by different letters are significantly different (Tukey, = 0.05) (SAS Institute 2008). Capital letters indicate differences between crop ages (main effects) and between crop ages at the same harvest resi due (interaction effects). Small letters indicate differences between harvest re sidue (main effects) and between harvest residues at the same crop age (interaction effects). 1No. stalks 1.5 m in height 2Weight (Kg) of individual millable stalk 3Sugarcane biomass yield in metric tons of cane per acre (TCA) 4Raw sugar weight in metric tons of sugar per acre (TSA), calculated from brix and pol values

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149 Table 5-4. Analysis of variance of harvesti ng method, tillage level and their interaction on E. lignosellus and other pests damage to sugarcane in 2008 and 2009 2008 Dead hearts1 Holes in leaves2 Total damage3 Other pests4 Source of variance df F P F P F P F P Harvesting method (HM) 1 769.78 <0.0001 366.52 <0.0001 833.14 <0.0001 0.10 0.7699 Tillage level (TL) 2 85.31 <0.0001 89.99 <0.0001 88.95 <0.0001 0.29 0.7551 HM TL 2 157.81 <0.0001 34.22 <0.0001 125.23 <0.0001 1.33 0.3066 Error 143 2009 Dead hearts Holes in leaves Total damage Other pests Source of variance df F P F P F P F P Harvesting method (HM) 1 940.37 <0.0001 867.16 <0.0001 1255.48 <0.0001 44.57 <0.0001 Tillage level (TL) 2 74.54 <0.0001 210.62 <0.0001 142.38 <0.0001 0.33 0.7228 HM TL 2 228.77 <0.0001 287.14 <0.0001 333.53 <0.0001 0.54 0.5908 Error 287 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Summation of dead hearts and holes in leaves 4Primary shoots and tillers with leaves damaged by other foliage f eeders (e.g. grasshoppers, armyworms)

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Table 5-5. Mean ( SEM) percentage damage by E. lignosellus and other pests to sugarcane in 2008 Treatment variables Main effects Dead hearts1Holes in leaves2 Total damage3 Other pests4 Green cane 07.6 0.4B 1.5 0. 1B 09.2 0.4B 0.4 0.1A Harvesting method Burnt cane 26.4 0.6A 7.0 0.1A 33.4 0.7A 0.3 0.1A No-tillage 15.1 0.5b 3.9 0. 3b 18.9 0.7b 0.4 0.1a Conventional 21.8 0.6a 5.9 0.5a 27.6 0.9a 0.4 0.1a Tillage level Intermediate 14.2 0.5b 3.2 0.3b 17.4 0.6b 0.3 0.1a Interaction effects Harvesting method Tillage level Dead hearts Holes in leaves Total damage Other pests No-tillage 0.93 0.2Bb 0.9 0.2Bb 01.8 0.3Bb 0.5 0.2Aa Conventional 20.4 0.9Aa 3.5 0.2Ba 23.9 1.0Aa 0.4 0.1Aa Green cane Intermediate 01.5 0.3Bb 0.2 0.1Bb 01.8 0.2Bb 0.4 0.2Aa No-tillage 29.2 0.8Aa 6.8 0.2Aa 36.0 0.9Aa 0.2 0.1Aa Conventional 23.1 0.9Aa 8.2 0.2Aa 31.3 0.8Aa 0.4 0.1Aa Burnt cane Intermediate 26.9 0.8Aa 6.1 0.2Aa 33.0 0.9Aa 0.2 0.1Aa Means followed by different letters in the columns are significantly different (Tukey, = 0.05) (SAS Institute 2008). Capital letters indicate differences between harvesting methods (main effects) and between harvesting methods at the same tillage level (interaction effects). Small letters indica te differences among tillage levels (main effects) and among tillage levels in the same harvesting method (interaction effects). 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Summation of dead hearts and holes in leaves 4Primary shoots and tillers with leaves damaged by other foliage feeders (e.g. grasshoppers, armyworms) 150

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151 Table 5-6. Mean ( SEM) percentage damage of E. lignosellus and other pests to sugarcane in 2009 Treatment variables Main effects Dead hearts1 Holes in leaves2 Total damage3 Other pests4 Green cane 05.1 0.2B 02.6 0. 1B 07.7 0.3B 4.9 0.7A Harvesting method Burnt cane 20.3 0.4A 10.8 0.2A 31.1 0.5A 2.6 0.3B Tillage level No-tillage 12.8 0.5b 06. 8 0.2b 19.6 0.6b 3.7 0.4a Conventional 14.5 0.5a 08.1 0.3a 22.6 0.7a 4.0 0.4a Intermediate 11.0 0.4c 05.2 0.2c 16.1 0.5c 3.6 0.3a Interaction effects Harvesting method Tillage level Dead hearts Holes in leaves Total damage Other pests Green cane No-tillage 01.9 0.1Bb 01.1 0.1Bb 03.0 0.2Bb 4.9 0.5Aa Conventional 11.9 0.5Ba 06.7 0.2Ba 18.6 0.7Ba 5.0 0.7Aa Intermediate 01.5 0.2Bb 00.0 0.0Bb 01.5 0.2Bb 4.7 0.5Aa Burnt cane No-tillage 23.6 0.7Aa 12.5 0.4Aa 36.1 0.8Aa 2.4 0.5Aa Conventional 17.0 0.4Aa 09.5 0.3Aa 26.5 0.3Aa 2.9 0.7Aa Intermediate 20.4 0.5Aa 10.3 0.2Aa 30.6 0.7Aa 2.4 0.5Aa Means followed by different letters in the columns are significantly different (Tukey, = 0.05) (SAS Institute 2008). Capital letters indicate differences between harvesting methods (main effects) and between harvesting methods at the same tillage level (interaction effects). Small letters indica te differences among tillage levels (main effects) and among tillage levels in the same harvesting method (interaction effects). 1Chlorosis and necrosis of only the primary shoot 2Primary shoots and tillers with symmetrical rows of holes in the leaves 3Summation of dead hearts and holes in leaves 4Primary shoots and tillers with leaves damaged by other foliage feeders (e.g. grasshoppers, armyworms)

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Table 5-7. Analysis of variance of harvesting met hod, tillage level, and their interaction on sugarcane yield traits in 2008 and 2009 2008 Source of variance Millable stalks1 Stalk weight2 TCA3 TSA4 df F P F P F P F P Harvesting method (HM) 1 4.63 0.0840 12.08 0.0177 17. 91 0.0082 1.16 0.3313 Tillage level (TL) 2 0.90 0.4366 0.86 0.4514 2.62 0.1217 1.75 0.2223 HM TL 2 2.94 0.0988 5.92 0. 0201 11.14 0.0029 9.26 0.0053 Error 143 2009 Source of variance Millable stalks Stalk weight TCA TSA df F P F P F P F P Harvesting method (HM) 1 47.66 <0.0001 29.29 0.0002 3. 22 0.1003 2.10 0.3120 Tillage level (TL) 2 0.63 0.5398 11.07 0.0005 9. 40 0.0011 3.31 0.0681 HM TL 2 1.36 0.2764 2.11 0. 1451 3.44 0.0501 7.10 0.0220 Error 287 1No. stalks 1.5 m in height 2Weight (Kg) of individual millable stalk 3Sugarcane biomass yield in metric tons of cane per acre (TCA) 4Raw sugar weight in metric tons of sugar per acre (TSA), calculated from brix and pol values 152

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Table 5-8. Mean ( SEM) sugarcane yield traits by harvesting method, tillage level and their interaction in E. lignosellus -infested fields during 2008 Treatment variables Main effects Millable stalks1 Stalk weight2TCA3 TSA4 Green cane 160.1 3.3A 0.65 0. 01A 33.2 0.6A 4.25 0.19A Harvesting method Burnt cane 153.6 3.2A 0.62 0.01B 30.2 0.5B 4.05 0.18A No-tillage 155.1 2.7a 0.62 0. 01a 30.9 0.6a 4.04 0.18a Conventional 155.9 2.3a 0.64 0.01a 31.7 0.7a 4.21 0.19a Tillage level Intermediate 159.6 2.8a 0.64 0.01a 32.5 0.7a 4.22 0.18a Interaction effects Harvesting method Tillage level Millable stalks Stalk weight TCA TSA Green cane No-tillage 160.9 3.6Aab 0.64 0.01Ab 33.1 0.8Aab 4.30 0.21Aa Conventional 154.2 3.5Ab 0.64 0.01Ab 31.3 0.7Ab 4.04 0.20Aa Intermediate 165.2 3.7Aa 0.67 0.01Aa 35.1 0.6Aa 4.42 0.23Aa Burnt cane No-tillage 149.3 3.8Ba 0.60 0.01Bb 28.7 0.6Bb 3.78 0.20Ab Conventional 157.6 3.9Aa 0.64 0.01Aa 32.0 0.7Aa 4.37 0.20Aa Intermediate 154.0 3.5Ba 0.61 0. 01Bab 29.8 0.6Bb 4.01 0.22Aab Means followed by different letters in the columns are significantly different (Tukey, = 0.05) (SAS Institute 2008). Capital letters indicate differences between harvest ing methods (main effects) and between harvesting methods at the sa me tillage level (interaction effe cts). Small letters indicate differences among tillage levels (main effects) and am ong tillage levels in the same harvesting method (interaction effects). 1No. stalks 1.5 m in height 2Weight (Kg) of individual millable stalk 3Sugarcane biomass yield in metric tons of cane per acre (TCA) 4Raw sugar weight in metric tons of sugar per acre (TSA), calculated from brix and pol values 153

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154 Table 5-9. Mean ( SEM) sugarcane yield traits by harvesting method, tillage level and their interaction in E. lignosellus -infested fields during 2009 Treatment variables Main effects Millable stalks1 Stalk weight2 TCA3 TSA4 Green cane 163.1 3.3B 0.73 0. 02A 37.9 1.2A 5.21 0.17A Harvesting method Burnt cane 173.8 3.4A 0.65 0.01B 36.1 1.2A 5.03 0.15A Tillage level No-tillage 167.5 3.3a 0. 65 0.02b 34.9 1.2b 4.98 0.16a Conventional 170.0 .4a 0.70 0.02a 37.8 1.3a 5.23 0.17a Intermediate 167.8 3.3a 0.72 0.03a 38.2 1.3a 5.23 0.16a Interaction effects Harvesting method Tillage level Millable stalks Stalk weight TCA TSA Green cane No-tillage 162.4 3.8Ba 0.70 0.02Ab 36.1 1.3Ab 5.10 0.18Ab Conventional 163.0 3.8Ba 0.72 0.03Ab 37.5 1.4Aab 5.20 0.19Aab Intermediate 163.8 3.9Ba 0.77 0.03Aa 40.1 1.4Aa 5.50 0.19Aa Burnt cane No-tillage 172.6 3.9Aa 0.61 0.02Bb 33.7 1.3Ab 4.86 0.18Ab Conventional 177.1 3.8Aa 0.67 0.02Aa 38.1 1.4Aa 5.25 0.19Aa Intermediate 171.8 3.8Aa 0.66 0. 02Bab 36.4 1.3Aab 4.98 0.18Bab Means followed by different letters in the columns are significantly different (Tukey, = 0.05) (SAS Institute 2008). Capital letters indicate differences between harvest ing methods (main effects) and between harvesting methods at the sa me tillage level (interaction effe cts). Small letters indicate differences among tillage levels (main effects) and among tillage levels in the same harvesting method (interaction effects). 1No. stalks 1.5 m in height 2Weight (Kg) of individual millable stalk

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CHAPTER 6 SUMMARY Sugarcane, Saccharum officinarum L. is an important crop grown in many southern temperate through tropica l regions of the world. Florida, Louisiana, Texas and Hawaii are the main sugarcane producing states in the U.S. Florida is the leading sugarcane producing state in the U.S. with 401,000 acres of sugarcane valued at $398.9 million dollars in 2008. There are seve ral factors that can result in decreased sugarcane yield, including insect damage. Lesse r cornstalk borer is an important pest of Florida sugarcane. Biological parameters of the lesser cornstalk borer, E. lignosellus life cycle were studied on different crops like cowpea, pea nut, southern pea, and soybean. Published studies on lesser cornstalk borer develop ment on sugarcane were conducted under uncontrolled, natural climatic co nditions. Therefore, it was not possible to determine the relationship between temperature and development rates of this pest on sugarcane. Also there was lack of knowledge regarding the effect of temperature on reproductive biology and life table paramet ers of lesser cornstalk bor er reared on sugarcane. Understanding the physiological relati onship between temperature, immature development and reproductive biology is im portant for the prediction of population outbreaks and timely management of pests. The first objective of this study was to determine the relationships between temperature and development and survivor ship of the immature stages of E. lignosellus on sugarcane under controlled te mperature conditions. The second objective was to study the reproductive biology and life table parameters of this pest at constant temperatures. 155

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To address the first objectiv e, the development of imma ture stages (eggs, larvae, pre-pupae, and pupae) of lesser cornstalk borer were observed on sugarcane at constant temperatures (13, 15, 18, 21, 24, 27, 30, 33, and 36 C), 65-70% relative humidity, and a photoperiod of 14: 10 (L:D) h. All immature stages of lesser cornstalk borer completed their development at temperatures from 13 C to 36 C. Developmental time decreased with increase in temperature from 13 to 33 C and then increased markedly at 36 C in all immature stages. Mean egg developmental time ( SEM) ranged from 1.8 0.1 d at 33 C to 17.5 0. 1 d at 13 C. The mean developmental time for larvae ranged from 15 .5 0.1 d at 33 C to 65.7 0.4 d at 13 C. Larvae completed six instars befor e pupating. Mean pre-pupal development ranged from 1.3 0.1 d at 33 C to 10.5 0.1 d at 13 C. Pupal development ranged from a mean of 5.9 0.1 d at 33 C to 29. 5 0.2 d at 13 C. Mean total development ranged from 22.8 0.3 d at 33 C to 120.7 2.8 d at 13 C. The mean survivorship rose with increasin g temperature for all immature stages, peaking at 27 C, and then decreasing with fu rther increases in temperature. At extreme temperatures (13 C and 36 C), percentage survival was quite low with 50% of eggs, larvae, pre-pupae and pupae surviving at 13 C. Egg and larval survival dropped below 50% at 36 C. Tem perature had a significant effect on the survival of all immature stages of E. lignosellus. One linear and six non-linear models were evaluated to describe the relationship between temperature and develop ment of immature stages. The linear model (without the data from 36 C) provided a good fit to the data in all immature stages with high r2 (> 0.96) and low RSS (< 0.027) and AIC (< -60.56) values. The linear regression model 156

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estimated that lesser cornstalk borer r equired 543.5 degree days (DD) to complete development from egg deposition to adult emergence on sugarcane with a lower developmental threshold of 9.5 C. Among all non-linear models, the Briere-1 model provided the best fit to the data with high r2 values, and low RSS and AIC values for each immature developmental stage. T he estimated lower and upper development thresholds for total imma ture development were 9.35 1.8 C and 37.90 0.7 C, respectively. To address the second objective, the reproductive, generation and population life table parameters of adult female lesser co rnstalk borer were studied at constant temperatures (13, 15, 18, 21, 24, 27, 30, 33, and 36 C), 65-70% relative humidity, and a photoperiod of 14:10 (L:D) h. Mean pre-oviposition peri od decreased with increase in temperature from 9.7 d at 13 C to 2.3 d at 33 C. Mean oviposition period was longest (4.6 d) at 27 C and decreased with increase or decrease in temperature. However, the post-oviposition period was shortest at 27 C (2.6 d) and increased with increase or decrease in temperature. Fecundity was also significantly affected by temperature and increased with increase in te mperature from 13 C to 30 C and decreased at 33 and 36 C. Temperature had a significant effect on stage specific survival rate (lx) and stage specific fecundity (mx) values. Both lx and mx increased with increase in temperature from 13 C to 30 C and decreased at 33 and 36 C. The temperatures of 27 C and 30 C were best for survival and fecundity of lesser cornstalk borer in sugarcane. The calculated life table parameters (r, R0, T, and DT) were also significantly affected by temperature. The value of r increased with increase in te mperature from 13 C (0.02) 157

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to 30 C (0.14) and then decreased at 36 C (0.07). Similarly, R0 was greatest at 30 C (65.2) and lowest at 13 C (9 .2). The value of T was greatest (130.5 d) at 13 C and lowest (27.6 d) at 33 C. The value of DT decreased with increase in temperature from 40.8 d at 13 C to 5.1 d at 30 C. The value of increased with increase in temperature from 1.02 at 13 C to 1.14 at 30 C and t hen decreased at 33 and 36 C. Six non-linear models were evaluated to describe the rela tionship between r and temperature. The Briere-2 model was the best fi t to the data with greatest r2 (0.9833) and r2 adj.(0.9733), and lowest RSS (0.0003) and AIC (96.14) values. Lesser cornstalk borer larvae enter the young shoot of sugarcane causing two types of damage. Larvae that reach the center of the shoot and damage or sever the youngest leaves produce dead he art symptoms. Non-lethal damage is caused when larvae only chew a few millimeters into the shoot and becomes evident when the leaves push out to reveal one to several symmetrical rows of holes. We observed a third type of damage in which shoots died in response to larval E. lignosellus feeding and did not produce tillers. Literature shows that in itial feeding damage does not always result in stand or yield loss in different crops. Based on this, our third objective was to determine the effect of lesser cornstalk borer damage on growth and yield of sugarcane plants. To address this objective, two, 11-mo greenhouse studies during 2008 and 2009 conducted at the Everglades Research and Education Center (E REC), Belle Glade, Florida. The sugarcane varieties CP78-1628, CP89-2143 and CP88-1762 were selected for this study. Three early growth stages (3-, 5-, and 7-leaf stage) were selected for infestation with lesser corn stalk borer larvae based on damage reports during the first 2-3 months of sugarcane growth. A randomized complete block design 158

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with a 3 4 factorial arrangem ent was used during both ex periment years to evaluate sugarcane response to E. lignosellus feeding damage. The factors were three sugarcane varieties (CP781628, CP88-1762, and CP89-2143) and three leaf stages infested plus one control (i.e., no infestation and infestation at 3-, 5-, and 7-leaf stages). The number of dead hearts, number of shoots wit h symmetrical rows of holes in leaves, and number of dead plants per bucket were re corded weekly starting one week after infestation at each leaf stage. The plant response to the damage was recorded as tiller production and yield traits. Sugarcane yi eld was determined using the number and weight of millable stalks, and the sucrose concentration of juice squeezed from those stalks. Results showed that CP89-21 43 had significantly greater percentage of plants with dead hearts, dead plants and total damage than other two varieties. The percentage of holes in leaves was greater in CP78-1628 t han other two varieties. Lethal damage as dead hearts and dead plants was greater in plants infested at 3-leaf stage and decreased with delay in infestation. Non-let hal damage as holes in the leaves was low at 3-leaf stage infestation and increased with delay in infestation. In response to lesser cornstalk borer damage, CP78-1628 and CP 88-1762 produced significantly greater number of tillers than CP89-2143 in both years. Bu ckets infested at 3-leaf stage produced significantly more tillers than those infested at 7-leaf stage in both years. In the variety leaf stage interaction, E. lignosellus damage at the 3-leaf stage to CP781628 and CP88-1762 resulted in increased tiller production over the untreated controls in both years. However, CP89-2143 plants in fested at all three le af stages produced significantly fewer tillers than the untreated control plants. In late infested plants, CP78159

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1628 produced more tillers than the other two varieties in 2008, but in 2009 both CP781628 and CP88-1762 produced more tillers than CP89-2143. Variations among varieties and leaf stages for millable stalk production were similar to tiller production. Sugarcane yield in CP78-1628 was significa ntly greater than in CP88-1762 and CP89-2143 in 2008, but in 2009 both CP78-1628 and CP88-1762 produced greater sugarcane yield than CP89-2143. Untreated control plants produced greater sugarcane yield than plants infested at all three leaf stages in both years. Plants infested at the 3and 5-leaf stages produced greate r sugarcane yield than those infested at the 7-leaf stage. In variety leaf st age interactions, infestation at the 3and 5-le af stages of CP78-1628 did not affect sugar cane yield compared to control, but infestation at the 7leaf resulted in significantly reduced yield. Although infestation at the 3-leaf stage in CP88-1762 resulted in more millable stalks produced than in the unt reated control, the sugarcane yield was greater in th e untreated control than in all the infested stages. In CP89-2143, plants in the untr eated control produced greater sugarcane yield than those infested at all the leaf stages Variations among varieties and leaf stages for sucrose yield were similar to sugarcane yield. Percentage compensation to initia l damage was calculated by deducting percentage reduction in yield from damage percentage. Overall, no significant difference was detected among the tested varieties for compensation for lesser cornstalk borer damage, but co mpensation was greater when in fested at 3followed by 5and 7-leaf stages in both y ears. In variety leaf stage interaction, CP78-1628 and CP88-1762 compensated better than CP89-2143 for sugarcane yield at 3-leaf stage infestation in 2009. However, sugarcane yiel d compensation following infestation at the 160

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7-leaf stage was greater in CP89-2143 than in CP78-1628. For sucrose yield compensation following infestation at the 7-leaf stage, CP89-21 43 compensated better than CP78-1628 and CP88-1762 dur ing both years. In CP78-1628 and CP88-1762, percentage compensation was signifi cant in the sequence of 3> 5> 7leaf stage. In CP89-2143, percentage compensat ion in the plants infested at the 3and the 5-leaf stage was same and it was greater than the plants infested at the 7-leaf stage. Compensation in sucrose yield was simila r to sugarcane yield compensation. Lesser cornstalk borer larvae are difficult to control with chemicals and biological control agents due to protecti on provided by silken tunnels. Many of the successful materials are no longer labeled for use on these or any other crops. Most recently, the United States Environmental Protection Ag ency revoked tolerances for carbofuran which was labeled for multiple insect controls in sugarcane, effectively removing the last of the effective products for controlling le sser cornstalk borer la rvae protected within plants. Cultural practices were reported to be efficient in lesser cornstalk borer in different crops, and needed evaluation in sugarcane. In fourth objective, two separate st udies were conducted in commercial sugarcane fields. In first study, we com pared the effects of trash blankets on lesser cornstalk borer damage and yield in plant cane versus ratoon sugarcane fields. The second study was designed to address grower concerns of reduced water percolation and fertilization penetration associated with tr ash blankets by comparing the combined effects of harvest method (green cane and burnt cane harvesting) and tillage levels (notillage, intermediate, and conventional ti llage) on lesser cornstalk borer damage and yield. 161

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In first study, an experiment was designed with a split plot design with plant and ratoon sugarcane fields as the main plots and plots with and without trash blankets as the sub plots. The data were recorded on feeding damage by lesser cornstalk borer as dead hearts, symmetrical rows of holes in leaves, and damage by other foliar feeders (e.g. grasshoppers, armyworms). The yiel d was estimated as sugarcane (TCA) and sucrose (TSA) yield. The results show ed that the plots wit h trash blankets had significantly reduced mean percentage of plants with dead hearts, holes in leaves and total damage. However, separation of t he means by interaction with the crop age determined that the presence of a trash blanket significantly affected lesser corn stalk borer damage only in the plant cane field. Damage by other foliar feeders was < 3% in both plant and ratoon cane fields. Plant c ane had significantly greater percentage of shoots damaged by other pests than ratoon cane. Trash blanket did not have a significant effect on damage by other pests ei ther in plant cane or in ratoon cane. Neither TCA nor TSA were affected by crop age, harvest residue or their interaction. In second study, the effects of harvest ing method (green harvest versus preharvest burning) combined with tillage level on damage caused by lesser cornstalk borer and sugarcane yield were evaluated during 2008 and 2009. The experimental design was again a split plot design with har vesting method (green cane versus burnt cane) as the main plots and tillage level ( no-, conventional and intermediate tillage) as sub-plots. Damage and yield dat a was recorded in the same way as in the first study. Plots in the field with pre-har vest burning had significantly greater percentages of plants with dead hearts, plants with holes in leaves, and total damage than in plots in the green harvested field in both years. Tillage le vels significantly affected lesser cornstalk 162

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borer damage in green cane harvested pl ots only, where again sub-plots with conventional tillage had greater percentages of plants with dead hearts, holes in leaves, and total damage than the sub-plot s with no-tillage and intermediat e tillage. Plots in the green harvested field had a great er percentage of plants damaged by other pests than burnt cane harvesting in 2009. Tillage level did not produce any significant effect on damage by other pests in main effects or in interaction with harvesting method during both years. Green cane harvested plot s produced greater TCA than burnt cane harvested plots in 2008, but t here was no difference in 2009. In green cane harvested plots, sub-plots with intermediate tillage had greater TCA than sub-plots with conventional tillage in 2008. In 2009, s ub-plots with intermedi ate tillage had greater TCA than sub-plots with no-t illage. In burnt cane harve sted plots, sub-plots with conventional tillage had greater TCA than sub-plots with no-till age and intermediate tillage in 2008, but the difference between conventional tillage and intermediate tillage was not significant in 2009. Based on these studies, it can be conclud ed that the temperature range of 27 C to 30 C are critical for population increas e due to high development rate, fecundity, survival rate and intrinsic rate of increas e. Green house studies showed that CP892143 is more susceptible to E. lignosellus damage than CP78-1628 and CP88-1762. Early infestation resulted in greater lethal damage than late infestation. Compensatory response to E. lignisellus damage was same among all the va rieties, but it was greater in early infested plants and decreased with delay in infestation. Field studies showed the positive effects of green harvesting and intermediate tillage for reducing E. lignosellus damage and increasing sugarcane yield. 163

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Further research is required to test the temperaturedependent development and population increase models in the field before t hey can reach their fu ll potential. Green house study could be conducted in the field to determine how season-long exposure to lesser cornstalk borers and population limiting factors (e.g., soil moisture and high summer soil surface temperatures) ma y affect damage throughout the season and resulting yields. 164

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LIST OF REFERENCES Agarwal, R. A. 1969. Morphological characteristics of sugarcane and insect resistance. Entomol. Exp. Appl. 12: 767-776. Aghdam, H. R., Y. Fathipour, G. Ra djabi, and M. Rezapanah. 2009. Temperaturedependent development and temperature thres holds of codling moth (Lepidoptera: Tortricidae) in Iran. Envi ron. Entomol. 38: 885-895. Akaike, H. 1974. A new look at the statistical model identification. IEEE Transactions on Automatic Control 19: 716-723. Akinsola, E. A. 1984. Effects of rice stem borer in festation on grain yield and yield components. Insect Sc i. Appl. 5: 91-94. All, J. N., and R. N. Gallaher. 1977. Deterimental impact of no-tillage corn cropping systems involving insecticides, hybrids, and irrigation on lesser cornstalk borer infestations. J. Ec on. Entomol. 70: 361-365. All, J. N., R. N. Gallaher, and M.D. Jellum. 1979. Influence of planting date, preplanting weed control, irrigation and conservation tillage practices on efficacy of planting time insecticide applications for control of lesser cornstalk borer in field corn. J. Econ. Entomol. 72: 265-268. Amir-Maafi. M., and H. Chi. 2006. Demography of Habrobracon hebetor (Hymenoptera: Braconidae) on two pyralid hosts (Lepidoptera: Pyralidae). Ann. Entomol. Soc. Am. 99: 84-90. Arthur, B. W., and F. S. Arant. 1956. Control of soil insect s attacking peanuts. J. Econ. Entomol. 49: 68-71. Banks, C. J., and E. D. M. Macaulay. 1967. Effects of Aphis fabae Stop. and of its attendant ants and insect predator s on yields of field beans (Vicia fahae L.). Ann. Appl. Bio. 60: 445-153. Bardner, R. 1968. Wheat bulb fly Leptohylemyia coarctata Fall. and its effect on the growth and yield of w heat. Ann. Appl. Biol. 61: 1-11. Bardner, R., and K. E. Fletcher. 1974. Insect infestations and their effects on the growth and yield of field crops: a review. Bull. Entomol. Res. 64: 141-160. Baucum, L. E., and R. W. Rice. 2009. An overview of Florida sugarcane. Available at http://edis.ifas.ufl.edu/sc032 (accessed on 30 March 2010). Bennett, F. D. 1962. Outbreaks of Elasmopalpus lignosellus (Zeller) (Lepidoptera: Phycitidae) in sugarcane in Barbados, Jama ica, and St. Kitts. Trop. Agric. Trin. 39: 153-156. 165

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Berberet, R. C., R. D. Morri son, and R. G. Wall. 1979. Yield reduction caused by the lesser cornstalk borer in nonirrigated Spani sh peanuts. J. Econ. Entomol. 72: 526528. Bessin, R. T., T. E. Reag en, and F. A. Martin. 1990. A moth production index for evaluating sugarcane cultivar s for resistance to the sugarcane borer (Lepidoptera: Pyralidae). J. Econ. Entomol. 83: 221-225. Birch, L. C. 1948. The intrinsic rate of natural incr ease of an insect population. J. Anim. Ecol. 17: 15-26. Bissell, T. L. 1945. Lesser cornstalk borer, pp. 63-64. In Annual Report, 1944-1945. Georgia Agric. Exp. Sta. GA. Bissell, T. L. 1946. Lesser cornstalk borer on cowpeas, pp. 82-84. In Annual Report, 1945-1946. Georgia Agricultural Experiment Station, GA. Blanchard, E. 1852. Gauna Chilena. USDA Entomol. Bull. 529. Box, H. E. 1929. Sobre las plagas insectiles de la cana de azucar. Rev. Ind. Agric. Tucuman 19: 212. Braxton L. B., and M. E. Gilreath. 1988. Differential injury by lesser cornstalk borer (Lepidoptera: Pyralidae) in soybeans of diffe rent growth stages. Fla. Entomol. 71: 656-657. Briere, J. F., and P. Pracros. 1998. Comparison of tem perature-dependent growth models with the development of Lobesia botrana (Lepidoptera: Tortricidae). Environ. Entomol. 27 : 94-101. Briere, J. F., P. Pracros, A. Y. le Roux, and J. S. Pierre. 1999. A novel rate model of temperature-dependent development for arthropods. Environ. Entomol. 28: 22-29. Bull, T. 2000. The sugarcane plant, pp. 71-83. In Manual of Cane Growing. Bureau of Sugar Experimental Stati ons, Indooroopily, Australia. Calvo, J. R. 1966. The lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and its control. Ph.D. disse rtation, University of Florida, Gainesville. Carbonell, E. E. T. 1977. Morfologia del barrenador menor de la cana de azucar Elasmopalpus lignosellus (Zeller) (Lepidoptera: Phyciti dae). Saccharum 5: 18-50. Carbonell, E. E. T. 1978. Descripcion de danos causados por Elasmopalpus lignosellus (Zeller) en cana de azucar y de algunos de sus controladores biologicos. Sacc harum 6: 118-145. Chalfant, R. B. 1975. A simplified technique for reari ng the lesser cornstalk borer. J. Ga. Entomol. Soc. 10: 33-37. 166

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BIOGRAPHICAL SKETCH Hardev was born in 1980 in Ahli Kalan, Punjab, I ndia. He received Bachelor of Science (hons.) in agriculture with major in plant protection from Punjab Agricultural University, Ludhiana, India in 2002. He started Master of Science degree in the Department of Entomology and Nematology under the supervision of Dr. Jaswant Singh in same institute. He was awarded with me rit scholarship during bachelors degree and fellowship from Monsanto during masters degree. Alongwith academics, he was a member of university team of folk danc e (Bhangra), and won several state-level and national-level competitions. He was also awarded with university meri t certificate both in academics and extracurricular activities. Afte r finishing his masters degree, he joined Indias topmost bank, State Bank of India as marketing and re covery officer in 2005. In spring 2006, he started Doctor of Philoso phy degree in Entomology and Nematology Department of University of Florida under the supervision of Dr. Gregg S. Nuessly. He started his project on biology and control of lesser cornstalk borer on sugarcane. During most part of his research work, he lived at Everglades Research and Education Center, Belle Glade, FL to complete fi eld and greenhouse experiments. During field research, he got a chance to interact wit h sugarcane growers of the area and United States Sugar Corporation and Florida Cystal personnels. He presented his research findings in several state and national level meetings. He also presented his research findings during extension meet ings at the Everglades Res earch and Education Center and nearby research stations. He received se veral research and travel grants from the department, university and also from scientific societies like Florida Entomological Society. He also served as a team leader in University of Floridas student debate team 178

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at 57th annual meeting of Entomological Society of America in Indianapolis. His future plans are to pursue his career in Integrated Pest Management. 179