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The lesser cornstalk borer Elasmopalpus lignosellus (Zeller), and its control

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The lesser cornstalk borer Elasmopalpus lignosellus (Zeller), and its control
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Calvo, Jose R., 1929-
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English
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vi, 70 leaves : ill. ; 28 cm.

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Chemicals ( jstor )
Corn ( jstor )
Eggs ( jstor )
Infestation ( jstor )
Insecticides ( jstor )
Insects ( jstor )
Larvae ( jstor )
Seedlings ( jstor )
Soils ( jstor )
Species ( jstor )
Borers (Insects) -- Biological control ( lcsh )
Dissertations, Academic -- Entomology and Nematology -- UF
Entomology and Nematology thesis Ph. D
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bibliography ( marcgt )
non-fiction ( marcgt )

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Thesis:
Thesis (Ph. D.)--University of Florida, 1966.
Bibliography:
Includes bibliographical references (leaves 62-64).
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Jose R. Calvo.

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THE LESSER CORNSTALK BORER

Elasmopalpus lignosellus (Zeller),

AND ITS CONTROL




















By
JOSE R. CALVO











A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY









UNIVERSITY OF FLORIDA

April, 1966












ACKNOWLEDGMENTS


The author expresses his appreciation to Dr. John T. Creighton for his interest and help in the conduct of this work, and for serving as chairman of his supervisory committee.

He is grateful to Dr. A. N. Tissot, Dr. L. C. Kuitert, Dr. V. G. Perry, and Dr. 0. C. Ruelke for their confidence and understanding as members of the supervisory committee, and for reviewing the manuscript.

Gratitude is expressed to Dr. L. C. Kuitert and Dr. D. H. Habeck, and to fellow graduate students Karl J. Stone, C. C. Russell, W. Yearian, and J. F. Matta for their encouragement and assistance during the course of this investigation.

Appreciation is expressed to Mrs. R. L. Linkfield and Dr. A. N. Tissot for their guidance in the preparation of the manuscript.

Thanks are extended to the Organization of American States, Dr. W. G. Eden, Chairman of the Department of Entomology, and Colonel G. A. Farris, Adviser to Foreign Students, for financial aid.



















ii













TABLE OF CONTENTS


ACKNOWLEDGMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . ii

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . iv

LIST OF FIGURES. . . . . . . . . . . . . . . . . . . . . . . . . . vi

INTRODUCTION ....................... . . .. . I 1

REVIEW OF LITERATURE . . . . . . . . . . . . . . . . . . . . . . . 3

Systematic History and Synonymy . . .............
Seasonal Occurrence ......... . .. ......
Cultural Control. . . . . . . . . . . . . . . . . . . . 6
Chemical Control.. ................ . . .. 9
Biological Control . . . . . . . . . . . . . . . . . . .. 13
Diets . . . . . . *. . . . . . . . ... . . 14

MATERIALS AND METHODS. . . . . . . . . . . . . . . . . . ... * 15

Rearing Phase . . . . . . . . . . . . . .. . . . . . . 15
Control Phase . . . ....... *. * * . .... *..... * 21

RESULTS AND DISCUSSION . . . . . . . . . . . . . . ... . . . 33

Rearing Phase . . ............... . . . ... . 33
Control Phase . ... . ........... . . . . . .. . 38

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . 59

LITERATURE CITED ................... ...... 62

APPENDIX ................... * * * .......... 65

BIOGRAPHICAL SKETCH. . . . . . . . . . . ... * * * . . . . . . . 71













iii











LIST OF TABLES


Table Page

1 Analysis of variance of corn plants surviving lesser
cornstalk borer attack after insecticide treatments in
Experiment No. 1. . . . . . . . . . . . . . . . . . . . . 41

2 Evaluation of insecticides of Experiment No. 1 applied
at 1 lb. of actual toxicant/acre to control lesser cornstalk borer larvae in corn seedlings. . . . . . . . . . . .. 42

3 Analysis of variance of corn plants surviving repeated
larval infestation after insecticide treatments in Experiment No. 2. . .. . . . . . . . . . . . . . . . . . . .. 44

4. Evaluation of residual effect of insecticides in Experiment
No. 2 applied at 1 lb./acre of actual toxicant to prevent
infestation of lesser cornstalk borer on corn seedlings . . . 45

5 Analysis of variance of corn plants surviving lesser cornstalk borer attack in light and heavy soils after liquid
and granular insecticidal treatments in Experiment No. 3. . . 47

6 Analysis of variance of corn plants surviving lesser cornstalk borer attack after seed treatments with insecticides
of Experiment No. 4 . . . . . . . . . . . . . . . . . . . 53

7 Evaluation of insecticides of Experiment No. 4, used as
seed treatments on Dixie 18 corn against infestation of
lesser cornstalk borer. . . . ..... ... . . . .. 54

8 Analysis of variance of corn plants surviving repeated
larval infestation after seed treatment with insecticides
of Experiment No. 5 . . . . . . . . . . . . . . . . . . . . 56

9 Evaluation of residual effect of insecticides of Experiment No. 5 used as seed treatments on Dixie 18 corn, against
repeated infestation with lesser cornstalk borer larvae . . . 57

10 Proportions of surviving corn plants from individual plots of Experiment No. 1 . . . . . . . ... . . . . . . . .. 66

11 Proportions of surviving corn plants from individual plots of Experiment No. 2 . . . . . . . . . . . . . . . . . . 67

12 Proportions of surviving corn plants from individual plots of Experiment No. 3 . . . . . . . . . . . . . . . . .. 68



iv













LIST OF TABLES (Continued)


Table Page

13 Proportions of surviving corn plants from individual
plots of Experiment No. 4 . . . . . . . . . . . . . . . 69

14 Proportions of surviving corn plants from individual
plots of Experiment No. . ....... ..... 70











































V











LIST OF FIGURES

Figure Page

1 Rearing cage on greenhouse bench. . . . . . . . . . . . . 16

2 Cages for mating and oviposition in bioclimatic chamber . 20 3 Adult male and female lesser cornstalk borer . . . . . . . 22 4 Larvae in different instars . . . . . . . . . . . . . . . . 23

5 Infested corn seedling showing larva and silk tunnel. . . . 24

6 Pupae; the pupa to the right shows the lack of sclerotization appearing after repeated artificial rearing. . . . . . 25

7 Open cocoon showing the pupa. . . . . .. . . . . . . . .. 26

8 Seedlings infested with eggs on paper strips. . . . . . . . 27

9 M4ean percentages of surviving corn plants after insectiside treatments against lesser cornstalk borer infestation in Experiment No. 1. . . . . . . . . . . . . . . . . . 40

10 Mean percentages of surviving corn plants after preventive
insecticidal treatments to test residual effect in Experiment No. 2. . . . . . . . . . . . . . . . . . . . . . 43

11 Lines showing the highly significant interaction between
soils and insecticides in Experiment No. 3. . . . ...... 48

12 Lines showing the significant interaction between formulation and insecticides in Experiment No. 3 . . . . . ... . 49

13 Mean percentages of corn plants surviving lesser cornstalk
borer infestation after insecticide treatments of Experiment No. 3 ............... . . ...... . 50

14 Mean percentages of corn plants surviving lesser cornstalk
borer infestation after insecticide seed treatments of Experiment No. 4. . . . . . . . . . . . . . . . 52

15 Mean percentages of corn plants surviving repeated infestation with lesser cornstalk borer larvae after insecticide seed treatments of Experiment No. 5. . . . . . . . . . 55





vi











INTRODUCTION


The lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), is a small moth of the family Phycitidae, subfamily Phycitinae. The larva is a pest of corn, field beans, peanuts, cowpeas, sugar cane, and wheat, particularly in the seedling stages.

This insect is distributed throughout the Western Hemisphere from southern United States to Argentina, and is of special economic importance in areas of light soils, and during dry periods. Infestations are sporadic,' usually affecting the later plantings.2

The larvae bore into the seedlings just below the soil surface, and tunnel upward into the stalk. From the entrance hole there extends into the soil a tube of silk and sand into which the larva withdraws when it is not feeding or when molested. Affected plants show signs of wilting in the bud leaves and die in a few days. Corn plants attacked in later stages are susceptible to lodging.

This insect has been known as an agricultural pest in the United

States since 1878. By 1903 it had become a serious pest of the above mentioned crops in southern United States.

Because of the subterranean habitat of the larva, and the fact that it appears sporadically, this insect has often been overlooked as a pest, its damage attributed to other causes. Surveys in the Gainesville area / in the springs of 1964 and 1965 showed some infested corn fields with about 20 percent of the plants attacked. Late corn plantings in the Pacific coastal areas of Central America are invariably affected by the



1





2





pest, with considerable reduction in stand.

Control of the lesser cornstalk borer is reported as impossible

once the larvae are inside the plants. Thus, recommended control measures rely on prevention by cultural or chemical methods when the presence of the pest is suspected.

The present work was undertaken to try to find methods of control which would not rely on prevention. Because natural infestations are sporadic and spotty, they do not provide satisfactory samples for field plot control experiments. Therefore, it was decided to mass-rear the insect, and to artificially infest the experimental plants to be sure mean-i ingful data would be obtained.

Since laboratory rearing limited larval numbers, and because of the impossibility of controlling excessive soil moisture and natural enemies in the field, the control trials were conducted in the greenhouse.











REVIEW OF LITERATURE


C. V. Riley (1881) reported Elasmopalpus lignosellus (Zeller), as an agricultural pest injuring corn near Augusta, Georgia. Studies at that time showed that the insect had not been known as a pest until about 1878. Luginbill and Ainslie (1917) completed the study of its life cycle, begun by Riley in 1881. Sanchez (1960) worked out the life ,cycle of the insect in Texas, and his observations and measurements coincide with those presented by Luginbill and Ainslie (1917). These last authors also reviewed the literature on the lesser cornstalk borer through 1917.


Systematic History and Synonymy

As reported by Luginbill and Ainslie (1917), the species was first described by Zeller as Pempelia lignosella in 1848, from material obtained from Brasil and Uruguay, and a single female from "Carolina," United States. In 1852 Blanchard redescribed the species as Elasmopalpus angustellus, erecting the genus Elasmopalpus which is now the accepted position for the species. In 1872 Zeller recorded it from Brasil, Colombia, "Carolina," and Texas, and added the descriptions of two varieties, incautella and tartarella, based on color variations. Each of these varieties was described from a single specimen, and both were taken at the same place on the same date. The species is extremely variable and Zeller in 1881 placed incautella as a symomyn of lignosella and retained tartarella as a valid variety. In 1874 Zeller described what he called "variety B" from material collected in Valparaiso, Chile. Berg in 1875 sup3












plemented Blanchard's description of Elasmopalpus anRustellus using material from Patagonia and other places in South America. He described venation in detail, and in 1877 concluded that Blanchard's angustellus was Zeller's lignosella, And that since both species were genotypes, the reduction of angustellus to a synonym of lignosella made Elasmopalpus a synonym of Pempelia. (According to Neave (1940) the genus Pempelia was erected by Huebner in 1825.) Zeller in 1881 published some notes on species variation based on 25 specimens from Colombia, South America. In 1888 Hulst redescribed the species as Dasypyga carbonella. In 1890 he rectified this and placed carbonella as a synonym of Zeller's variety tartarella. In the same publication he redescribed lignosellus and placed it in the genus Elasmopalpus for the first time, giving a bibliography and notes on the distribution and seasonal occurrence. In 1893 Ragonot published on the synonymy and bibliography, and gave a description of the species, calling attention to its great variability. He also used the name major, the first word in Zeller's description, for "variety B", and listed it as a variety of the species lignosellus. Smith in 1900 recorded the species for New York, and Dyar in 1902 listed it with synonyms, stating that it is distributed in the Atlantic States and South America. Ainslie (1917) came to the conclusion that the use of varietal names in this species could be discontinued. The varieties described are not constant in any respect, and apparently indicate individual aberrations in color, size, or markings. The synonymy then is reported as follows:





5






Pempelia lignosella Zeller 1848

Elasmopalpus angustellus Blanchard 1852

Pempelia lignosella tartarella Zeller 1872 Pempelia lignosella incautella Zeller 1872

Dasypyga carbonella Hulst 1888

Elasmopalpus lignosellus (Zeller) Hulst 1890

Elasmopalpus lignosellus incautellus (Zeller) Hulst 1890 Elasmopalpus lignosellus tartarellus (Zeller) Hulst 1890 Heinrich (1956) reported the following synonymy:

Elasmopalpus lignosellus (Zeller)

Pempelia lignosella Zeller 1848

Elasmopalpus angustellus Blanchard 1852

Pempelia lignosella tartarella Zeller 1872 Pempelia lignosella incautella Zeller 1872

Pempelia lignosella malor Zeller 1874

Elasmopalpus anthracellus Ragonot 1888

Dasypyga carbonella Hulst 1888

Elasmopalpus lignosellus (Zeller) Ragonot 1889

Elasmopalpus puer Dyar 1919 (new synonymy).


Seasonal Occurrence

The occurrence of four generations a year in the latitude of Columbia, South Carolina, was suggested by Luginbill and Ainslie (1917), who also stated their belief that at that latitude the insect passes the early part of the winter in the larval stage, and the latter part as pupae, and possibly adults. They also reported that the species












probably overwinters in the larval stage in Arizona.

The Quarterly Bulletin of the Mississippi Plant Board (1927) reports four generations a year, each taking from five to seven weeks, and states that the insect hibernates in the pupal stage in the soil.

Vorhies and Wehrle (1946) reported that three generations occur in Arizona in a year, and that the insect probably overwinters in the soil in the larval stage.

Harding (1960) observed that as a pest of peanuts in Texas this insect is a problem only in the fall, and that injury occurs about two weeks after plant emergence, and continues until harvest.

Sanchez (1960),also working in Texas, suggested that the overwintering stage apparently varies from one area to another, depending on winter severity.

The seasonal infestation of southern peas at Experiment,Georgia, was illustrated graphically by Dupree (1964). Infestation starts at under 1 percent before June 1, climbs to 5 percent on July 15, reaches a peak of 17 percent on August 15, and ends the first week of September. These percentages were the averages of five years.


Cultural Control

Luginbill and Ainslie (1917) recommended late fall or early winter plowing after freeing the fields from all crop residues as the best practice for preventing infestation. They also recommended disking field borders and terraces to stir the ground and break up the winter quarters of the pupae, and fertilization of sandy areas to stimulate growth and make plants more resistant. Early planting of corn and sorghum was
/





7






suggested to enable the plants to get a good start before heavy infestation occurs. Cowan and Dempsey (1949) recommended thorough ground preparation to prevent borer damage to pimiento in Georgia.

An apparent correlation between crop residues in the field before planting and the degree of infestation was observed by Isley and Miner (1944). They suggested inspection of underground stems of food plants before planting to determine whether a thorough soil preparation was necessary in order to kill half grown larvae. They believed that larvae from eggs deposited after planting would not have time to develop to destructive size before the plants passed the most susceptible stage of growth. This view was shared by Reynolds et al. (1959), Wilson and Kelsheimer (1955), and Dupree (1964). The last author also stated that plowing under natural food and immediately planting a crop often results in concentrated feeding by the borer on the emerging plants. Dupree (1964) in a 1959 experiment combining cultural practices and chemical control, kept land free of weed growth by tillage prior to summer planting of southern peas. This resulted in control of lesser cornstalk borer superior to that obtained with insecticides. Isley and Miner (1944) Indicated that partial destruction of weed hosts hastens larval migration to the new crop and Reynolds et al. (1959) considered that cultivating out all infested hosts can be disastrous as it forces virtually the entire resident borer population to feed on the crop seedlings.

Box (1929) recommended eradication of barnyardgrass Echinochloa crusgalli from ug r cane fields in Cuba as a method of control. Stahl (1930) attributed infestations on strawberries to grass weeds in the beds.












Isley and Miner (1944) found that infestation of autumn beans in Arkansas in 1943 occurred following a spring crop of beans and a heavy growth of crabgrass Digitaria spp. Dupree (1964) indicated that planting legumes after plowing weedy small grain stubble promoted an ideal situation for borer damage to cowpea seedlings in Georgia. In the Quarterly Bulletin of the Mississippi Plant Board (1927) it is reported that cowpeas and soybeans are more subject to attack following plantings of corn.

Plank (1928) reported from Cuba that burning trash after harvest

of sugar cane favors infestation because'the trash prevents growth of wild hosts in the field. This was confirmed by Ingram et al. (1939) in Louisiana. On the other hand, Hayward (1943) recommended clean cultivation and manuring of sugar cane in Tucuman, Argentina, to prevent infestation.

Stuckey (1945), and Bissell and Dupree (1947) reported a 2/3 reduction of infested cowpea plants when nitrogen, phosphorus, and potassium fertilizer was used, as compared to non-fertilized plots.

Pulling and destroying all infested crop plants was recommended by Watson (1917) and Lauderdale (1920).

Reynolds et al. (1959) used flood irrigation to control infestations on sorghum in California.

The Report of the Puerto Rico Experiment Station (1937) mentions that small seeded bush-type varieties of lima beans show some resistance to the borer.












Chemical Control

Literature on the use of chemical insecticides against the lesser corrstalk borer is not abundant, and the work reported describes preventive insecticidal treatments rather t-han control of infestations.

Isley and Mi-ner (1944) obtained unsatisfactory control with a )plications of calcium arsenate and cryolite to the lower surfaces of the leaves and to the stems of bean plants against mirating larvae in Kansas. Willie (1942) tried 3 percent DDT dust and 4 percent benzene hexachloride, corresponding to 0.4 percent gam _a isomer on beans in Peru, and reported that benzene hexachloride gave complete control of the larvae in a week. 4 Dugas et al. (194S) in Louisiana, obtained perfect stands of corn in soils treated with 1 lb. parathion, 1.5 1bs. liniang, or 2.5 lbs. of chlordane per acre, each of which was much more effective thLn DSC. Kulash (1948), in North Carolina, obtained some control on snap beans with 3 percent lindane plus 5 percent DDT dust at the rate of 10 lbs. per acre, and with 60 grams of 50 percent DDT wettable powder in one gallon of water per 50 feet of crop row, applied to the base of the plants. This author reports between 30 and 40 percent control, by sampling enough plants to observe 10 larvae per treatment. Reduction of damage to sweet corn and green corn withy early applications of DDT and chlordane was obtained in Florida by Kelsheimer et al.(1950), who concluded that no satisfactory control is known for this insect. Hills et al.(1953) confirmed that satisfactory control procedures for the lesser cornstalk borer have not been worked out, and reported reduction of damage to bush snap beans in Florida with applications of 2 lbs. per acre of parathion wettable powder in 100 gal. of water. The





10







spray was applied to the base of the stems before cultivation which might cover the silk tunnels with soil, thus protecting the larvae from the chemical. Hyche and Eden (1954) obtained control of this pest on cow peas in Alabama with i lb. endrin per acre, applied to the rows as a spray or broadcast as granules, at the time of plant emergence, with two subsequent applications at weekly intervals. Wilson and Kelsheimer (1955) reduced damage to cowpeas in Florida with 5 percent chlordane at the rate of 25 lbs. per acre applied to the rows just before the seedlings emerged. The same authors pointed out that the borers cannot be reached 4 with insecticides after they enter the plants.

Reduced damage to peanuts in Alabama was obtained with the use of

2.5 percent DDT or 10 percent toxaphene for control of leaf-feeding insects. Dust applications of DDT, benzene hexachloride, chlordane, toxaphene and aldrin in the drill at the time of sowing reduced damage to peanuts, but yields did not increase significantly. Similar treatments in emulsion form did not reduce damage. Treatments ich -ranular aldrin and dieldrin at the rate of 2 lbs. per acre, and with toxaphene at 6 lbs. per acre, were applied to the soil surface at the time the pods began to reach the soil; this resulted in reduced damage and increased yields significantly. All these treatments were applied against several insect pests of peanuts, including the lesser cornstalk borer, Arthur and Arant (1956).

Reynolds et al. (1957) tried seed treatments on sorghum and soybeans with phorate and disulfoton at the rate of 1 lb. to 25 lbs. of seed, and by drilling 2 percent granules of both materials with the sorghum seed at the rate of 1 lb. of technical material per acre. Seed germination and













stand of both crops were severely affected by the treatments, and little or no reduction of borer infestation was obtained. Falanghe (1958) applied 20 percent toxaphene dust, and 0.4 percent parathion at the rate of 12 lbs. per acre of wheat, followed by a low volume spray of 0.25 percent methyl demeton, or this spray alone. Both treatments improved the appearance of the plants and increased yields significantly.

Successful control, according to Reynolds et al. (1959), depends on preventive applications of chemical insecticides. They reported control with endrin, aldrin, heptachlor, and dieldrin. These insecticides were applied in spray and granular form at the time of plant emergence on sorghum planted in seed beds 40 inches apart; no control was obtained, however, when the seeds were planted flat and at closer distances. The Rh chemicals were applied at the rate of eight ounces per acre in concentrated bands. These authors hold that insecticides are ineffective after the larvae have become established in the plants.

Cunningham et al. (1959) tried endrin treatments at the rate of

0.4 lbs. per acre in 20, 40, and 86 gallons of water applied to the base of peanut plants at monthly intervals to coincide with successive generations of moths, as determined by Sanchez (1960) in that area, and at intervals of 7, 14, and 21 days. There was a significant reduction of injury in all cases.

Harding (1960) obtained chemical control with granular applications of 2 lbs. per acre of DDT, or 1 lb. per acre of disulfoton, parathion, phorate, or dieldrin. Sprays of 0.5 lbs. of endrin, parathion, azinphosmethyl, or isobenzan; 0.75 lbs. per acre of endosulfan, or 1 lb. per acre




12






of DDT, in five to ten gallons of water were the most effective materials tested; however, their residual effects were limited by the sprinkler irrigation used. These treatments were applied to the base of the plants at the time of moth emergence.

Sanchez (1960) conducted control experiments on peanuts with DDT, endrin, demeton, azinphosmethyl, mevinphos, and Chlorothion (0,0-dimethyl 0-(3-chloro-4-nitrophenyl) thiophosphate) sprays; and with dust applications of endrin, dieldrin, heptachlor, DDT, and toxaphene. None of these treatments gave significant control.

Dupree (1964) conducted a series of control experiments on legumes in Spalding County, Georgia, from 1959 to 1964. In one test he tried granular applications of 5 percent DDT, and 20 percent toxaphene at the rate of 5 lbs. per acre; 2.5 percent heptachlor at 0.5 and 2 lbs. per acre; 2 percent and 5 percent aldrin at 2 lbs. per acre; and 5 percent dieldrin at 2 lbs. per acre. These were protective treatments on southern pea seedlings, and all showed significant reduction in the number of dead plants. In another test 2.5 percent heptachlor, disulfoton, AC 528 (2,3-p-dioxanedithiol S,S-bis(O,0-diethyl phosphorodithioate), and azinphosmethyl, at rates of 2, 1.5, 0.5, and 0.5 lbs per acre respectively; and 5 percent dieldrin at 0.5 lbs. per acre, all in granular form were tried. Heptachlor and disulfoton gave significantly more effective control. Granules of 5 percent aldrin at 8 lbs. per acre, and 2.5 percent heptachlor at 16 lbs. per acre were compared with Bacillus thuringiensis (Thuricide Dust 10 D) at 20 lbs. per acre. Both aldrin and heptachlor were more effective than the bacterium. In another test granular applica-





13





tions of 5 percent aldrin and 2.5 percent heptachlor at the rate of 0.4 lbs. per acre; and 10 percent benzene hexachloride and DDT at the rates of 0.6 lbs. and 1 lb. per acre respectively were tried under conditions of clean and weed-fallow cultivation. Clean-fallow cultivation prior to summer planting of cowpeas resulted in control superior to that obtained from insecticides, although the insecticides were beneficial in reducing losses in the absence of this cultural practice. An experiment with dust applications of 0.3 lbs. per acre of dieldrin, 4 lbs. per acre of toxaphene, 2 lbs. per acre of DDT, 0.5 lbs. per acre of heptachlor, and 0.4 lbs. per acre of endrin gave no significant stand protection. Sprays with emulsions of aldrin at 0.5 lbs. per acre; methoxychlor, at 1 lb. per acre; endrin at 0.5 lbs. per acre; and trichlorfon wettable powder at 0.5 lbs. per acre, in 77 gallons of water, gave significant reduction of damage for aldrin. These same treatments,plus dieldrin emulsion at 0.5 lbs. per acre in 300 gallons of water, gave significant reduction of damage for aldrin and endrin. Another experiment with emulsion treatments of aldrin, lindane, and heptachlor at 2 lbs. per acre, dieldrin at 1 lb. per acre, and endrin, mevinphos, and endosulfan at 0.5 lbs. per acre in 300 gallons of water applied to a 5 inch band at planting time, gave no significant differences for treatments.


Biological Control

Luginbill and Ainslie (1917) believed that the lesser cornstalk borer suffers very little from natural enemies due to the excellent protection afforded the larvae by feeding burrows and silk tubes. Leuck and Dupree (1965) listed the currently identified insect parasites of the





14






borer and their abundance in the Piedmont and Coastal Plain regions of Georgia, and stated that parasitism is a contributing factor to the population variations which make this insect a sporadic pest. They reported the following parasites: On the eggs:

1. Telenomus (Telenomus) n. sp. (Scelionidae, Hymenoptera)

2. Chelonus (Nicrochelonus) n. sp. (Braconidae, Hymenoptera) On the larvae:

1. Pristomerus pacificus melleus Cushman (Ichneumonidae, Hymenoptera)

2. Orgilus n. sp. (Braconidae, Hymenoptera)

3. Bracon mellitor Say (Braconidae, Hymenoptera)

4. Stomatomyia floridensis Townsend (Tachinidae, Diptera)

5. Plagiprospherysa parvipalpis (Wulp) (Tachinidae, Diptera)

Parasitism in different samples of larvae collected from soybeans and cowpeas during July and August fluctuated between 35 and 60 percent, with S. floridensis being the dominant species, followed by Orgilus n. sp. and P. pacificus melleus.

Leuck (personal communication) has since added Pristomerus pacificus appalachianus Viereck (Ichneumonidae, Hymenoptera) to this list. L'


Diets

The diet recommended by Berger (1963) for rearing larvae of Heliothis species was adopted for rearing lesser cornstalk borer larvae. This diet is described on page 18 under Material and Methods.












MATERIALS AND METHODS


This study was conducted from May, 1964 to October, 1965, and consisted of two phases: 1. the establishment of a laboratory population; 2. control experiments conducted in the greenhouse. The laboratory population was necessary because suitable samples could not be obtained from natural infestations due to the sporadic nature of the pest.


Rearing Phase

Lesser cornstalk borer larvae were collected in May, 1964, from corn seedlings in the Gainesville, Florida, area. They were transferred inside their sand tubes to potted corn seedlings inside screen cages where they were reared to maturity. The moths were then fed a 10 percent solution of honey in water. The rearing cages measured 25 x 15 x 15 inches. Pieces of cellucotton or paper towel were provided for oviposition. To supplement the small population obtained from field collected larvae, two ultraviolet light traps were run throughout the period, and adults were collected from the middle of July to September, 1964, when the moths ceased to come to the traps.

In order to rear a larger population than the potted seedlings allowed, a large screen cage was built over a greenhouse bench (Figure 1). This cage was 12 x 3 x 2 feet, and was provided with three cloth sleeves for access. A sliding panel left 3/4 of the space as a nursery where the tissue strips with the attached eggs were placed on closely planted corn seedlings. The remaining 1/4 of the space was used for concentration and collection of the adults, which were attracted to it by a light,


15






16




















'21 Figure 1. Rearing cage on greenhouse bench.






17





and collected in this compartment by pushing in the sliding panel and picking them up with a shell vial. The adults were then transferred to screen cages 9 x 9 x 5 inches in size, where mating and oviposition took place. These cages, on stilts, were placed on water pans to prevent ants from preying on the eggs. The adults were fed 10 percent honey in water, with 1 gram of sorbic acid added per 500 cc of diet to prevent mold. The eggs were laid on paper towels placed on top of the cages.

The following artificial diets were tried when it became evident that a population sufficiently large to carry out infestation of the experimental plants could not be obtained from the greenhouse rearing:

1. Macerated corn seedlings in agar, with methyl p-hydroxybenzoate and sorbic acid as preservatives, tried with and without the fiber, and in different proportions of agar and water.

2. A diet consisting of the following ingredients devised by W.

Yearian, a fellow graduate student at the University of Florida:

1. macerated corn 100 g 2. water 300 cc 3. agar 12 g 4. sucrose 5 g 5. fructose 5 g 6. vitamin fortification mixture 2 g 7. soybean protein 10 g 8. peanut oil 1 cc






18





9. cholesterol 0.5 g

10. Wesson's salts 1.0 g 11. yeast 5.0 g 12. choline chloride 0.1 g 13. glycine - 15.0 g 14. cysteine 15.0 g 15. tegosept 0.5 g 16. sorbic acid 0.5 g

3. The following diet recommended by Berger (1963) for rearing

larvae of Heliothis species was adopted for rearing lesser

cornstalk borer larvae:

1. distilled water 208.5 cc 2. 22.5 percent KOH 4.3 cc 3. casein 29.2 g 4. Wesson's salts 8.5 g 5. sucrose 22.7 g 6. 10 percent formaldehide 3.1 cc

7. Mixture of: 7 g methyl p-hydroxybenzoate +
7 g sorbic acid in 50 cc of 95 percent ethyl alcohol 12.5 cc 8. wheat gern 25.6 g 9. alphacel 4.3 g 10. vitamin fortification mixture 8.5 g 11. agar, hot, dissolved in 521 cc of water 21.3 g 12. ascorbic acid 3.4 g

13. streptomycin sulfate (700 micrograms/ml.) 118.0 mg






19






These diets were placed in petri dishes, on sterilized sand in mason jars; or in shell vials 19 mm in diameter and 7 cms in height. Pieces of paper towel with eggs attached were placed on or near the diet, or newly hatched larvae were placed on the diet using a camel hair brush.

Rearing in the shell vials on the wheat germ base diet (Berger 1963) was finally adopted because preliminary trials showed this to be the best. The diet was prepared in a blender. Approximately 5 cc of the freshly mixed warm diet were placed in each sterilized vial with a plastic dispenser bottle. Then the pieces of paper towel with one to several eggs were placed in the vials, without contact with the diet, and held in place with a cotton plug. The vials were then kept in drawers, under each of which a 60 watt electric bulb was placed to maintain the temperature at 30 to 350C. A glass container with water in each drawer prevented drying of the diet. The larvae completed development in about three weeks, and the pupae were removed from the vials with a metal hook and placed in syracuse dishes which were then transferred to screen cages measuring 9 x 9 x 6 inches (Figure 2). These were kept in a bioclimatic chamber at 270C, and 40 to 50 percent relative humidity, and with 14 hour periods of light. At emergence, the moths were fed the above mentioned honey in water diet.

About seventy larvae were started each week in as many vials; a total of four hundred vials was used for this work.

Observations were made on the number and size of larval instars

and their duration in laboratory rearing. The number of eggs per female






20















































Figure 2. Cages for mating and oviposition in bioclimatic
chamber.






21





was estimated as indicated on page 35 under Results and Discussion. Photographs were taken of the insect in different stages of development (Figures 3, 4, 5, 6, and 7).


Control Phase

Dixie 18 corn seedlings were infested with eggs or larvae in different instars, Infestation from eggs was obtained by cutting the paper towels used for oviposition into small pieces, with at least two eggs on each; these paper pieces were glued to the stem when the seedlings were in the two leaves stage. Another method was to place a layer of dry soil at the base of the seedlings and sink the paper pieces with the eggs into the soil in contact with the stems (Figure 8).

Third or fourth instar larvae were also used for infestation. A larva was extracted from the vial with a metal hook and placed on dry loose soil at the base of each seedling in contact with the stem. A half pint paper cup with the bottom removed was placed around each seedling to discourage the larvae from wandering away.

The seeds were planted in rows on greenhouse benches, and bands

of vaseline applied to the legs of the benches to keep predatory ants out. Soil moisture was kept at a minimum to favor infestation.

Six experiments in control using chemical insecticides were conducted from July to November, 1965. Two greenhouses 20 x 15 feet were screened for this purpose.

The common names of insecticides used in this work follow the designations given by Billings (1963 and 1965). The chemical names of proprietary compounds used follow; subsequent reference to these compounds





22























































Figure 3. Adult male and female lesser cornstalk borer.





23






























I













Figure 4. Larvae in different instars.






24












































Figure 5. Infested corn seedling showing larva and silk tunnel.





25















































Figure 6. Pupae; the pupa to the right shows the lack of
sclerotization appearing after repeated artificial
rearing.





26















































Figure 7. Open cocoon showing the pupa.





27













































Figure 8. Seedlings infested with eggs on paper strips.





28






will be by their proprietary names or code numbers: Bayer 251411--0,0-diethyl 0-p-(methylsulfinyl) phenyl phosphorodithioate. Bayer 390071--0-isopropoxyphenyl methylcarbamate. Bidrin2--dimethyl phosphate of 3-hydroxy-N,N-dimethyl-cia-crotonamide. G.C. 65063--dimethyl p-(methylthio) phenyl phosphate. Kepone3--decachlorooctahydro-l,3,4-metheno-2H-cyclobuta [cd] pentalen-2one.


Experiment No. 1.

The purpose of this experiment was to screen fifteen insecticides which appeared promising for control of the lesser cornstalk borer, either from reported effects in the prevention of this insect, or in control of similar pests. A greenhouse bench 33 inches wide and 5 inches deep was filled with Kanapaha fine sand and divided with plastic strips into 48 sections 9 inches wide and 33 inches long. On July 28, 1965, two rows of ten seed each of Dixie 18 corn were planted in each section, equidistant from each other and from the plastic walls. On August 4, when the seedlings were in the two leaves stage and about 3 inches high, paper strips with 3-day-old eggs were placed on them as described previously. By this method 100 percent infestation of the plants was obtained. The experiment was laid out in a completely randomized design with three replications per treatment and two seedling rows per replicate. On August 13, when about 10 percent of the seedlings had begun to show signs of infestation, and the larvae were in the third and fourth instars, the following

1Provided by Chemagro Corporation.
2Provided by Shell Chemical Company.
3Provided by Allied Chemical Corporation.





29






insecticides were applied at the rate of 1 lb. active material per acre in 50 gallons of water: Bayer 25141, Bayer 39007, Bidrin, diazinon, dimethoate, disulfoton,1 .trichlorfon,l endrin,2 ethion, G. C. 6506, azinphosmethyl, heptachlor,2 Kepone, phorate, and endosulfan.

Bayer 39007, trichlorfon, and Kepone were used as wettable powders; phorate was used in granular form since no liquid form or wettable powder was available. All the other insecticides were used in emulsion form. The liquid applications were made with a plastic bottle and directed to the base of the plants. Phorate granules were applied in a narrow band at the base of the plants. At the time of treatment, and 15 days after treatment, the number of healthy plants per experimental unit was counted. Experiment No. 2.

Four of the chemical insecticides which appeared most effective in experiment no. 1 were tried for residual effect in a completely randomized design with four replications. Each replicate consisted of two rows of ten seeds each of Dixie 18 corn planted in units of the same size as in experiment no. 1, and with the same distance between tl- seed rows and the plastic walls limiting the unit. The seeds were planted on September 1, 1965, on Kanapaha fine sand, and treated on September 10, when at the two leaves stage, with the following insecticides in emulsion form applied to the base of the plants at the rate of 1 lb. of active material per acre in 50 gallons of water: Bayer 25141, diazinon, endrin, and G.C. 6506.


1Provided by Chemagro Corporation.

2Provided by Velsicol Chemical Corporation.






30





On September 15, when the plants were about six inches high, they were infested with one-fourth instar larva per plant. On September 25, when the plants were about 15 inches high, another fourth instar larva was placed on the soil at the base of each plant. Healthy living plants were counted on October 13.


Experiment No. 3.

Four of the better performing insecticides from experiment no. 1, which were available in both granular and emulsifiable formulations were evaluated in a split-split plot design with three randomized blocks, using a heavy soil (Fellowship loamy fine sand), and a light soil (Kanapaha fine sand) as main plots; formulation as sub-plots; and insecticides as sub-sub-plots. The experimental units were similar to those described, except that the seedling rows were only 30 inches long.

Dixie 18 corn seed was planted on September 10, 1965, and infested on September 18 with mature eggs. Plants in sandy soil showed signs of infestation first, and were treated on September 27. Those on clay soil were treated on October 4.

Endrin, diazinon, Bayer 25141, and dimethoate were used in emulsion form at the rate of 1 lb. active material per acre, in 50 gallons of water, and in granular form at 2 lbs. active material per acre. Both the emulsion and granules were applied in narrow bands at the base of the plants.

Healthy, living plants in sandy soil were counted on October 12, and those on clay soil on October 16.





31






Experiment No. 4.

The same group of insecticides, except phorate, used for control in experiment no.1, were tried as seed treatments on Dixie 18 corn, at the rate of 1 lb. of technical material to 100 lbs. of seed, except G.C. 6506 used at 0.5 lbs/100 lbs. and Bidrin used at both 1 lb. and 0.5 lbs/100 lbs. of seed, following observations from preliminary trials.

For each treatment 1 ounce of seed was placed in a 100 cc glass

jar, and a pipette used to add the proper amount of the corresponding insecticide in emulsifiable concentrate, or wettable powder form. Twelve hours after being mixed with the chemical, the seed was planted in Kanapaha fine sand in a greenhouse bench. A completely randomized design was used, with three replications. The experimental units were similar to those of previously described experiments. The seed was planted on August 15, 1965, the seedlings were infested with eggs when at the two leaves stage, on August 24, an the healthy living plants counted on September 10. Experiment No. 5.

This experiment was performed to study with more precision the effects as seed treatments, and the residual effects of some of the better performing chemicals from experiment no. 4. Dixie 18 corn seed from the 1964 harvest was used. The seed was treated with diazinon and Bayer 39007 at the rate of 0.75 lbs./100 ibs, endrin, Zidrin, and Bayer 25141 at 0.5 lbs./100 ibs, and with G.C. 6506 at 0.25 lbs./100 lbs. It was found necessary to determine tolerable dosages of insecticides for the new seed.

The seed was treated in the manner described for experiment no. 4, and planted in Zuber loamy fine sand on September 12, 1965, twelve hours





32





after treatment. A completely randomized design with four replications was used; the experimental units had the same characteristics as those in former experiments. Paper strips with 3-day-old eggs were placed on the seedlings on September 18. On September 22 and again on September 30, one fourth instar larva was placed at the base of each plant. The proportions of healthy living plants were determined on October 10.












RESULTS AND DISCUSSI


Rearing Phase

Rearing of the larvae in the wheat base diet (Berger 1963) was successfully carried out in shell vials; however, rearing on corn seedlings in the greenhouse was continued as a source of material in case of need. This greenhouse rearing had allowed observations on the development of larvae in corn seedlings, and served as a guide for infesting the experimental plants in chemical control trials, and for determining how much time could elapse between the appearance of signs of infestation and the treatment. Moreover, this greenhouse population showed the existence of many more males than females at the beginning and the end of the season, and also the fact that over-wintering occurred in the pupal stage and had diapause characteristics.

The selected diet was prepared as described by Berger, 1963, poured in the shell vials, and kept under refrigeration until needed. At first, a sterilized camel hair brush was used to place a newly hatched larva in each vial. This procedure was later abandoned, for the more expedient one of cutting the paper towels used for oviposition into strips with one or more eggs on them, and placing these strips in the vials in such a manner as to avoid contact with the diet which inhibited hatching.

Pupation occurred between 15 and 40 days after hatching, with most larvae pupating in about 22 days. Due to this variation in time, it was difficult to rear more than one larva per vial, as some of the pupae were preyed upon by slow developing larvae.




33






34





The use of eggs on paper strips for rearing caused fungal contamination in some of the vials, making the diet unfit and causing the death of the larvae. The number of contaminated vials, however, was never large. The contaminating fungi were of the genera Rhyzopus and Aspergillus. The mite Tyrophagus putrescentiae (Schrank), which preyed on the eggs in the bioclimatic chamber, was also introduced into some of the rearing vials, where it proliferated abundantly and caused death of the larvae. Few vials were infested if the oviposition cages were withdrawn every 15 days from the chamber and cleaned, and the temperature in the chamber was raised to 600C for 20 minutes before replacing the cages. This procedure also checked the saw-toothed grain beetle, Oryzaephilus surinamensis (L), and the cigarette beetle, Lasioderma serricorne (Fab.), which established populations in the ovipositing cages. Ants were kept out by placing the cages on a table with the legs in jars with water.

A continuous population was maintained in this manner from June, 1964. After three successive generations were reared on the diet, a small percentage of the pupae appeared in which the wing pads were poorly developed, and there was a lack of sclerotization over the 3rd and 4th abdominal segments of the pupal case (Figure 6). At emergence the pupal case split across that poorly sclerotized area leaving a hood over the head and thorax from which the adults could not escape. Addition of 60 grams of macerated corn seedlings to 873 grams of diet eliminated this problem, making it unnecessary to replace the population.

The use of sorbic acid in the honey in water fed to the adults made it possible to keep the diet for a week; during this time only water was added to the cotton wads previously saturated with the diet.






35




Thirty-five newly emerged females and thirty-five males were

placed in an oviposition cage in the bioclimatic chamber on August 5, 1965. An average of sixty-seven eggs per female was obtained; oviposition occurred as follows:

August 8 156 eggs August 15 87 eggs August 9 255 eggs August 16 301 eggs August 10 340 eggs August 17 0 eggs August 11 462 eggs August 18 173 eggs August 12 458 eggs August 19 115 eggs August 13 0 eggs August 20 57 eggs August 14 12 eggs August 21 30 eggs

The number of larval instars and their respective sizes were

found to coincide with those reported by Luginbill and Ainslie (1917), and Sanchez (1960). Duration of these larval instars was approximately as reported by Luginbill and Ainslie (1917) for the months of September and October in Columbia, South Carolina.

A large population of lesser cornstalk borers, needed for conducting research in chemical control, could not be established from larvae collected in the field because small numbers of adults were obtained, and no mating took place in the rearing cages unless there were about 10 moths per cubic foot, with equal proportions of both sexes. Mated females from light traps were collected in increasing numbers from June to September of 1964, but a working population could not be established because very few specimens were collected during humid periods. An abundance of eggs from females collected in light traps permitted rearing of a large popu-






36





lation merely by placing eggs deposited on paper towels along the corn seedling rows growing in a screened greenhouse bench. This greatly improved rearing technique had two serious limitations: 1. It was impossible to have enough seedlings at all times to maintain a large, constant population, and fluctuations in the population size made the conduct of control experiments very difficult. 2. Extreme humidity in the second and third weeks of September 1964, which put an end to light trap collections of the insect, also considerably decreased the greenhouse population; oviposition diminished and most of the eggs did not hatch. By the end of September, 1964, emergence of adults in the greenhouse rearing cage ceased despite the fact that the temperature was maintained between 270C and 320C throughout the winter. Adults did emerge from pupae sifted out of the rearing cage sand and extracted from the cocoons; however, not enough of them were obtained to begin a population, because of the need to leave sufficient overwintering pupae to resume the rearing the following spring, in the event a population could not be carried through the winter. Another disadvantage of the greenhouse rearing was the constant need to control grease ants Monomorium pharaonis, which preyed on the eggs and larvae of the lesser cornstalk borer. This problem was solved, however, by the use of a Kepone peanut butter bait.

In an effort to expedite the rearing operation, and to control the number of insects being reared, artificial diets were tried unsuccessfully in 1964. Although some partly grown larvae continued to develop in both macerated corn in agar, and in the Yearian diet described in materials and methods, most larvae failed to complete development. Newly hatched larvae could not be established on the first diet although several changes were






37





made in it. Some larvae were reared on the second diet, but mortality was too high to justify its use over the rearing in corn seedlings.

In the spring of 1965, rearing was resumed from adults emerging

from overwintering pupae in the greenhouse rearing bench. Another source of the borer was found in a heavy infestation on experimental plots of Rhodesgrass Chloris gavana, in Hague, Florida. Five hundred larvae were collected and brought to the greenhouse where development continued on corn seedlings. A later collection of two hundred larvae from the same source was reared to maturity on the wheat germ base diet (Berger 1963) by placing the diet on sterilized sand in glass jars 7 inches in diameter and 3 inches in height. These larvae were brought from the field in their sand tunnels, extracted with a Berlese funnel, and placed in the jars with the diet.

About 20 percent of the last group of larvae were parasitized by Orgilus n. sp. (Braconidae, Hymenoptera). Also three specimens of Pristomerus pacificus melleus Cushman (Ichneumonidae, Hymenoptera) were recovered. These parasites were sent to the United States National Museum for identification.

The glass jars used to rear field collected larvae in the wheat base diet (Berger 1963), were used to rear larvae from the first instar, but they were not satisfactory because contamination of the diet with fungi, primarily Rhyzopus nigricans, and Aspergillus sp. was almost unavoidable, and because slow developing larvae preyed on the pupae from faster growing larvae.





38





Control Phase

Eggs used to infest experimental plants hatched within 24 hours. First instar larvae buried under the dry layer of sand at the base of the plants after wandering about the stem; some larvae climbed to the leaves and fed there for a while before boring into the stems under the soil line. Some plants began to show signs of infestation about ten days after hatching of the eggs, when the larvae were in the fourth or fifth instar, but since only a small percentage of the larvae attained that stage of development in ten days, it was possible to obtain good control by treating within approximately three days of the appearance of signs of infestation. Affected plants showed wilting of the bud leaves. Stunting effects were not noticed up to the appearance of wilting. Some of the plants showing signs of infestation died, their number depending on the delay between the appearance of signs and treatment, and on the type of treatment. Many of these plants recovered with the treatment, but were counted as surviving only when they did not show signs of stunting. The experimental plants grew more slender, and less vigorous than they normally would have grown in the field, and probably were more susceptible to the attack of the borer. There was 100 percent infestation of the experimental plants, and in some experiments all control plants died.

Infestation trials showed it was best to use third and fourth instar larvae. Younger larvae were hard to handle, and older ones were very restless, and wandered away from the seedling on which they were placed. Third or fourth instar larvae would immediately enter the soil around the stem and start building a tunnel. Seedlings attacked by mature larvae




39





toppled in a few hours without showing any signs of infestation. Experiment No. 1.

The mean percentage of surviving plants per treatment is presented . in histogram form in Figure 9. An arcsine transformation was made on the proportions of surviving plants, and the transformations were submitted to analysis of variance (Table 1). Treatment effects were highly significant, and a Duncan's test was used to compare treatment means (Table 2).

Treatments with Bayer 25141, G. C. 6506, diazinon, endrin, dimethoate, azinphosmethyl, trichlorfon, phorate, disulfoton, Bidrin, and Bayer 39007 gave highly significantly better control than the untreated plots. A highly significant difference was obtained between Bayer 25141 and Bayer 39007, the first being more effective.


Experiment No. 2.

The four insecticides used were highly effective in preventing infestation by partially grown larvae, although each corn seedling was infested with mature larvae on two different dates. The mean percentages of surviving plants are presented in histogram form in Figure 10, which shows the small percentage of survival in the untreated plots. An arcsine transformation of the proportions of surviving plants was submitted to analysis of variance (Table 3). There were highly significant treatment effects; a Duncan's test for treatment means was performed (Table 4). G.C. 6506, endrin, Bayer 25141, and diazinon were all highly significantly better than the control, with no significant difference among them.













Percent plant survival


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41






TABLE 1

ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING LESSER CORNSTALK BORER
ATTACK AFTER INSECTICIDE TREATMENTS IN EXPERIMENT NO. 1



Source of Degrees of Sum of Mean Variation Freedom Squares Square


Total 47 31,041.45 Treatments 15 23,792.14 1,586.14** Error 32 7,249.31 226.54



**Significance at the 1% level.





42






TABLE 2

EVALUATION OF INSECTICIDES OF EXPERIMENT NO. 1 APPLIED AT 1 LB.
OF ACTUAL TOXICANT/ACRE TO CONTROL LESSER CORN STALK BORER LARVAE IN CORN SEEDLINGS


Mean Surviving Plants
Treatment Percent Arcsine* check 0.0 0.00 a Kepone 6.3 14.53 ab endosulfan 21.0 27.93 abc ethion 32.2 34.56 abcd Bayer 39007 35.8 36.76 bcd Bidrin 50.1 45.06 bcde disulfoton 59.1 50.20 bcde heptachlor 71.2 57.53 cde phorate 73.0 58.66 cde trichlorfon 74.1 59.36-cde azinphosmethyl 81.3 64.43 de dimethoate 86.4 68.40 de endrin 89.1 70.73 de diazinon 89.6 71.23 de G.C. 6506 92.0 73.43 de Bayer 25141 98.4 82.66 e

*Any two means followed by the same letter are not significantly different at the 1% level. Significance based on Duncan's test.





43













100


90


80


70


60


d 50


S40
so.
te 0 S30 * or U, o 'o 0 20 o 0 L0

U, N O
0
10 0 0n





Figure 10. Mean percentages of surviving corn plants after
preventive insecticidal treatments to test residual effect in Experiment No. 2.




44









TABLE 3

ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING REPEATED LARVAL INFESTATION AFTER INSECTICIDE TREATMENTS IN EXPERIMENT NO. 2



Source of Degrees of Sum of Mean Variation Freedom Squares Square

Total 19 18,663.08 Treatments 4 16,080.57 4,020.14** Error 15 2,582.51 172.16



**Significance at the 1% level.





45






TABLE 4

EVALUATION OF RESIDUAL EFFECT CFINSECTICIDES IN EXPERIMENT NO. 2 APPLIED AT 1 LB./ACRE OF ACTUAL TOXICANT TO PREVENT INFESTATION
OF LESSER CORNSTALK BORER ON CORN SEEDLINGS



Mean Surviving Plants
Treatment Percent Arcsine* check 3.00 9.80 a diazinon 93.40 75.12 b Bayer 25141 96.60 79.35 b endrin 97.00 79.90 b G.C. 6506 99.55 86.17 b


*Any two means followed by the same letter are not significantly different at the 1% level. Significance based on Duncan's test.





46






Experiment No. 3.

Treatments in this experiment were applied somewhat late for

best results. Treatments on heavy soil were delayed because soil moisture was harder to keep at a minimum in this soil, and the plants did not show signs of infestation early enough. An arcsine transformation of the proportions of surviving plants was submitted to analysis of variance (Table 5). There was a highly significant interaction between soil and chemical insecticides (Figure 11). Endrin and diazinon gave the best control on both types of soil, whereas Bayer 25141 gave about the same level of control in heavy soil as did endrin and diazinon, but a much lower one in light soil. Dimethoate was poor in both soils.

The interaction between formulation and chemical insecticides

(Figure 12), was significant at the 5 percent level. The four chemicals gave better control in liquid application despite the fact that twice as much technical material was used in the granular applications. The histogram in figure 13 shows the mean percentage of surviving plants per treatment across the experiment.


Experiment No. 4.

Several preliminary trials had to be made to determine the effect of the treatments on seed germination and stand, in order to determine the proper dosage. Dosages never exceeded 1 lb. of technical material per 100 lbs. of seed, because it was not possible to add more material with the procedure used. Plants from seed treated with G.C. 6506, Bayer 25141, and diazinon showed some signs of toxicity, but recovered in about

8 days and did not appear different from plants in other treatments.





47






TABLE 5

ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING LESSER CORNSTALK BORER
ATTACK IN LIGHT AND HEAVY SOILS AFTER LIQUID AND GRANULAR
INSECTICIDAL TREATMENTS IN EXPERIMENT NO. 3



Source of Degrees of Sum of Mean Variation Freedom Squares Square MAIN PLOTS

blocks 2 222.26 111.13 soil, S 1 113.70 113.70 error a 2 126.40 62.20 SUB PLOTS

formulation, F 1 1,195.37 1,195.37 SF 1 22.62 22.62 error b 4 814.75 203.68 SUB-SUB PLOTS

insecticides, I 4 29,783.87 7,445,96 SI 4 3,310.21 827.55** FI 4 630.88 157.72* SFI 4 99.54 24.88 error c 32 1,316.95 41.15


*Significance at the 5% level. **Significance at the 1% level.






48











100 90 80

.endrin 70on > 60


50
-e5

40 S30


20
dimethoate 10


light soil heavy soil
Figure 11. Lines showing the highly significant interaction
between soils and insecticides in Experiment No. 3.





49












100 90 80


70 diagno > 60
LIBayer 25141 r 50
4'

r 40


30 20


10 d


0
granular emulsion

Figure 12. Lines showing the significant interaction
between formulation and insecticides in
Experiment No. 3.





50













100 90 80


70 0 60


Cd
50


u 40
N
30

00
t0 o
20









ments of Experiment No. 3.
10 04 0





Figure 13. Mean percentages of corn plants surviving lesser
cornstalk borer infestation after insecticide treatments of Experiment No. 3.






51





Plants from seed treated with Bidrin looked more vigorous than those from untreated seed in this experiment. Figure 14 shows the mean percentage of plant survival per treatment. An arcsine transformation was made on the proportions of surviving plants, and the transformations submitted to analysis of variance (Table 6). There was a highly significant difference for treatments. A Duncan's test of comparisons among treatment means (Table 7) showed that Bidrin, Bayer 25141, diazinon, endrin, heptachlor, Bayer 39007, and azinphosmethyl at 1 lb./100 lbs.; G.C. 6506 and Bidrin at 0.5 lbs./100 lbs.; and G. C. 6506 at 0.25 lbs./100 lbs. were highly significantly better than the check. These chemicals provided protection against larvae developing from egg infestations. Dimethoate, trichlorfon, Kepone, endosulfan, disulfoton, and ethion did not differ from the check at the 1 percent level. Experiment No. 5.

This experiment had to be repeated because germination was completely inhibited by seed treatments of Bayer 25141 at 1 lb./100 lbs. and G.C. 6506 at 0.5 lbs./100 lbs., and severely reduced by endrin at 1 lb./ 100 lbs. Dixie 18 corn seed of the 1965 crop was used, and germination trials had to be made to determine that B 25141, G.C. 6506, and endrin could be used safely at rates of 0.5, 0.25, and 0.5 lbs./100 lbs. respectively. Figure 15 shows a histogram of mean percent plant survival per treatment. The analysis of variance of the transformed proportions is presented in Table 8. There was a highly significant difference for treatments, and a Duncan's test (Table 9) showed that endrin, Bayer 25141,
















Percent plant survival


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53







TABLE 6

ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING LESSER CORNSTALK BORER ATTACK AFTER SEED TREATMENTS WITH INSECTICIDES OF EXPERIMENT NO. 4



Source of Degrees of Sum of Mean Variation Freedom Squares Square Total 50 33,351.46 Treatments 16 25.420.88 1,588.80** Error 34 7,930.58 233.25


**Significance at the 1. level.





54





TABLE 7

EVALUATION OF INSECTICIDES OF EXPERIMENT NO. 4, USED AS SEED TREATMENTS
ON DIXIE 18 CORN AGAINST INFESTATION OF LESSER CORNSTALK BORER



Mean Surviving Plants
Treatment Percent Arcsine* check 1.20 6.13 a ethion (1 lb./100 lbs.) 9.80 18.20 ab disulfoton " 12.30 20.53 ab endosulfan " 16.70 24.13 abc Kepone " 17.70 24.86 abc trichlorfon " 31.50 34.20 abcd dimethoate " 35.30 36.53 abcd azinphosmethyl " 57.30 49.23 bcde Bidrin (0.50 lbs./100 lbs.) 66.50 54.66 bcde G.C. 6506 (0.25 lbs./100 lbs.) 76.40 60.93 cde Bayer 39007 (1 lb./100 lbs.) 82.60 65.33 de heptachlor " 83.20 65.83 de endrin " 87.10 68.93 de G.C. 6506 (0.50 lbs./100 lbs.) 89.00 70.06 de diazinon (1 lb./100 lbs.) 89.00 70.33 de Bayer 25141 " 89.00 70.63 de Bidrin " 95.50 77.73 e


*Any two means followed by the same letter are not significantly different at the 1% level. Significance based on Duncan's test.










100 90


80 70


S60 50 . . 50 20 M Yd




10
30 o 0 0


20







Figure 15. Mean percentages of corn plants surviving repeated infestation with
lesser cornstalk borer larvae after insecticide seed treatments of
Experiment No. 5.





56







TABLE 8

ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING REPEATED LARVAL
INFESTATION AFTER SEED TREATMENT WITH INSECTICIDES OF EXPERIMENT NO.5



Source of Degrees of Sum of Mean Variation Freedom Squares Square Total 27 13,905.53 Treatments 6 9.738.21 1,623.03** Error 21 4,167.32 198.44


**Significance at the 1% level.





57






TABLE 9

EVALUATION OF RESIDUAL EFFECT OF INSECTICIDES OF EXPERIMENT NO. 5 USED AS SEED TREATMENTS ON DIXIE 18 CORN, AGAINST REPEATED
INFESTATION WITH LESSER CORNSTALK BORER LARVAE



Mean Surviving Plants
Treatment Percent Arcsine* check 10.70 19.10 a diazinon (0175 lbs./100 lbs.) 27.60 31.75 ab Bayer 39007 " 47.10 43.30 abc Bidrin (0.50 lbs./100 lbs.) 55.80 48.32 abc endrin " 62.00 51.95 bcd Bayer 25141 " 82.30 65.15 cd G.C. 6506 (0.25 lbs./100 lbs.) 96.80 79.70 d


*Any two means followed by the same letter are not significantly different at the 1% level. Significance based on Duncan's test.




58





and G.C. 6506 were highly significantly better than the check, whereas diazinon, Bayer 39007, and Bidrin were not significantly different from the check at the 1 percent level.













SUMMARY AND CONCLUSIONS


Control of the lesser cornstalk borer has been reported as impossible once the larvae are within the plants.

The sporadic and spotty manner in which infestations by this pest occur does not afford satisfactory samples for field plot experiments in control.

In this work, the lesser cornstalk borer was mass-reared in the laboratory. The larvae were grown in a wheat germ base diet devised for rearing larvae of Heliothis species (Berger 1963). For mating and oviposition, the adults were placed in screen cages at a concentration of at least ten moths per cubic foot, with equal proportions of males and females. The cages were kept in a bioclimatic chamber at about 270C and 60 percent relative humidity, and with 14 hour periods of light.

Measurements and observations of the different stages of the insect were made and found to coincide with those made by Luginbill and Ainslie (1917) and Sanchez (1960).

Greenhouse experiments in chemical control were conducted on artificially infested seedlings of Dixie 18 corn. A layer of dry soil was placed around the seedlings and infestation carried out by sinking paper strips with eggs in the soil in contact with the stem, or by placing third or fourth instar larvae on dry loose soil at the base of the seedlings.

Highly significant control was obtained with treatments of Bayer

25141, G.C. 6506, diazinon, endrin, dimethoate, azinphosmethyl, heptachlor, disulfoton, and Bidrin in emulsion form; trichlorfon and Bayer 39007





59





60






wettable powders, and phorate granules. The insecticides were applied to the base of the plants at the rate of 1 lb. of active material per acre soon after the first signs of infestation appeared.

G.C. 6506, endrin, Bayer 25141, and diazinon applied to the base of the seedlings in emulsion form at the rate of 1 lb. of active material per acre gave a high level of protection against subsequent infestation with fourth instar larvae.

Infested seedlings in light and heavy soil were treated with endrin, diazinon, Bayer 25141, and dimethoate at the rate of 1 lb. per acre in emulsion form, and 2 lbs. per acre in granular form. Endrin and diazinon gave the best control on both types of soil, whereas Bayer 25141 gave about the same level of control in heavy soil as did endrin and diazinon, but a much lower one in light soil. Dimethoate was poor in both soils. The four chemicals gave better control in liquid applications, despite the fact that twice as much technical material was used in the granular applications.

When Dixie 18 corn seed was treated with Bidrin, Bayer 25141,

diazinon, endrin, heptachlor, Bayer 39007, and azinphosmethyl at the rate of 1 lb./100 lbs. of seed, and with G.C. 6506 at 0.25 lbs./100 lbs. of seed, the seedlings were given a highly significant level of protection.

In one experiment to test the residual effect of several insecticides applied as seed treatments, endrin, Bayer 25141, and G.C. 6506 were highly significantly better than the check. In this test, however, endrin and Bayer 25141 caused phytotoxicity at rates higher than 0.5 lbs./100 lbs. of seed.






61





Signs of infestation began to show about ten days after the plants were infested, and for the following three or four days, appeared in from

5 to 10 percent of the infested plants. A high percent of control was obtained with some insecticides if the treatment was made during those three or four days, in which case even the plants showing signs of infestation recovered. Mortality of the seedlings was almost 100 percent in the untreated plots.

Chemical insecticides are effective in the control of lesser cornstalk borer attacking corn seedlings, especially when the chemicals are applied in water to the base of the plants, if the treatments are made soon after the appearance of signs of infestation.











LITERATURE CITED

Anonymous. 1937. Report of the Puerto Rico Experiment Station. 115 pp.
Washington, D. C. 1939 Rev. Appl. Entomol. Ser. A. 27:501.

Arthur, B. W. and F. S. Arant. 1956. Control of soil insects attacking peanuts. J. Econ. Entomol. 49(1):68-71.

Berger, R. S. 1963. Laboratory techniques for rearing Heliothis species on artificial medium. USDA, ARS-33-84.

Billings, S. C. 1963. Consolidated list of new approved common names of insecticides and other pesticides. Bull. Entomol. Soc. Am. 9(3):
189-197.

. 1965. Consolidated list of approved common names of insecticides and certain other pesticides. Bull. Entomol. Soc. Am. 11
(3): 204-213.

JBissell, T. L. and M. Dupree. 1947. Vegetable insect pests. Georgia
Agric. Exp. Stat. Bull. 254:7-8.

Box, H. E. 1929. Sobre las plagas insectiles de la cana de azucar. Rev.
Ind. Agric. Tucuman 19(7-8):212.

Cowan, F. F. and A. H. Dempsey. 1949. Pimiento production in Georgia.
Georgia Agric. Exp. Sta. Bull. 259:17.

Cunningham, W. H., Jr., D. R. King, and B. C. Langley. 1959. Insecticidal control of the lesser cornstalk borer. J. Econ. Entomol.
52(2): 329-330.

Dugas, A. L., C. E. Smith, and E. J. Concienne. 1948. Parathion found effective against the fall armyworm and the lesser cornstalk borer.
In Louisiana Agric. Exp. Sta. Annu. Rept. p. 70-71.

Dupree, M. 1964. Insecticidal and cultural control of the lesser cornstalk borer. Georgia Experiment Sta. Mimeo. Ser. 197.

Falanghe, 0. 1958. O combate as pragas do trigo proporciona melhores colheitas. Biologico 24(3):42-45.

SHarding, J. A. 1960. Control of the lesser cornstalk borer attacking
peanuts. J. Econ. Entomol. 53(4):664-667.

Hayward, K. J. 1943. La polilla taladradora de la cana de azucar (Elas mopalpus lignosellus (Zeller). Bol. Est. Exp. Agric. Tucuman 49:9.

' Heinrich, C. 1956. American moths of the subfamily Phycitinae. U. S.
Nat. Mus. Bull. 207.



62






63





Hills, W. A., J. F. Darby, W. H. Thames, and W. T. Forsee. 1953. Bush snap bean production on sandy soils of Florida. Florida Agric.
Exp. Sta. Bull. 530:22.

Hyche, L. and W. G. Eden. 1954. Control of the lesser cornstalk borer on beans and peas. In Alabama Agric. Exp. Sta. Annu. Rept. 64-65:
50.

Ingram, J. W., H. A. Jaynes, and R. N. Lobdell. 1939. Sugar cane pests in Florida. In Proc. Int. Soc. Sug. Cane Tech. 6:89-98.

J Isley, D. and F. D. Miner. 1944. The lesser cornstalk borer, a pest of
fall beans. J. Kansas Entomol. Soc. 17 (2): 51-57.

Kelsheimer, E. G., N. C. Hayslip, and J. W. Wilson. 1950. Control of budworms, earworms, and other insects attacking sweetcorn and green
corn in Florida. Florida Agric. Exp. Sta. Bull. 466:31-36.

Kulash, W. M. 1948. Benzene hexachloride-DDT combination for pest control. J. Econ. Entomol. 41 (6):912-913.

Lauderdale, J. L. E. 1920. Annual report of the assistant entomologist at Yuma. llth. Annu. Rept. Arizona Commis. Agric. & Hort. 19181919. 1921. Rev. Appl. Entomol. Ser. A (9):408.

J Leuck, D. B., and M. Dupree. 1965. Parasites of the lesser cornstalk
borer. J. Econ. Entomol. 58 (4): 779.

Luginbill, P.,and G. G. Ainslie. 1917. The lesser cornstalk borer. USDA Ent. Bull. 539.

o Lyle, C. 1927. The lesser cornstalk borer (Elasmopalpus lignosellus
(Zeller)). Mississippi State Plant Bd. Quart. Bull. 7 (2):2-3.

Neave, S. A. 1940. Nomenclator Zoologicus. Vol. III. Zoological Society of London. 1065 pp.

Plank, H. K. 1928. The lesser cornstalk borer (Elasmopalpus lignosellus (Zeller)) injuring sugar cane in Cuba. J. Econ. Entomol. 21 (2):
413-417.

Reynolds, H. T., T. R. Fukuto, R. L. Metcalf, and R. B. March. 1957.
Seed treatments of field crops with systemic insecticides. J.
Econ. Entomol. 50 (5): 527-539.

Reynolds, H. T., L. D. Anderson, and L. A. Andres. 1959. Cultural and chemical control of the lesser cornstalk borer in southern California. J. Econ. Entomol. 52 (1): 63-66.






64





' Riley, C. V. 1882. The smaller cornstalk borer (Pempelia lignosella
Zeller). In USDA Rept. 1881. pp. 142-145.

Sanchez, L. 0. 1960. The biology and control of the lesser cornstalk
-borer, Elasmopalpus liqnosellus (Zeller). Unpublished Doctoral
dissertation, Texas Agricultural and Mechanical College.

Sauer, H. F. G. 1939. Notas sobre Elasmopalpus lignosellus (Zeller) (Lepidoptera, Pyralidae) seria praga dos cereais no estado de
Sao Paulo. Arq. Inst. Biol. pp. 199-206.

Stahl, C. F. 1930. The lesser cornstalk borer (Elasmopalpus lignosellus,
(Zeller)) attacking strawberry plants. J. Econ. Entomol. 23 (2):
466,

jStuckey, H. P. 1945. The lesser cornstalk borer. Georgia Exp. Sta.
57th Annu. Rept. pp. 63-64.

Vorhies, C. T. and L. P. Wehrle. 1946. Pest problems of the small garden. Arizona Agric. Exp. Sta. Bull. 203:32-33.

Watson, J. R. 1917. The leser cornstalk borer (Elasnropalpus lignosellus (Zeller)). Florid- Agric. Exp. Sta. Bull. 134:54.

Willie, J. E. 1942. insectos cue atacan a las leguminosas cultivadas.
Vida Agricola 19 (222):347-349.

Wilson, J. W., and E. G. Kalsheimer. 1955. Production of southern peas in Florida. Insects and their control. Florida Agric. Exp. Sta.
Bull. 557:18.



































APPENDIX











TABLE 10

PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 1



REPLICATIONS
Treatments I II III

1. endosulfan 7/16 0/7 5/11 2. disulfotan 7/18 9/10 8/19 3. G.C. 6506 14/17 16/16 14/17 4. check 0/14 0/9 O/IZ 5. endrin 16/17 12/14 13/15 6. azinphosmethyl 15/17 8/19 9/12 7. diazinon 10/13 10/10 11/14

8. Bidrin 0/8 5/10 5/9 9. trichlorfon 5/13 9/9- 7/12 10. dimethoate 11/13 10/11 10/12 11. Bayer 25141 10/10 10/10 12/14 12. ethion 0/8 7/11 6/10 13. Kepone 0/11 2/15 2/14 14. heptachlor 17/19 6/10 9/15 15. phorate 11/17 12/14 10/15 16. Bayer 39007 6/17 5/15 7/18





67






TABLE 11

PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 2



REPLICATIONS
Treatments I II III IV

1. endrin 9/11 10/10 13/14 10/10 2. check 4/10 0/10 0/13 0/14 3. Bayer 25141 10/11 9/9 9/11 16/16 4. diazinon 11/11 12/13 7/8 11/13 5. G.C. 6506 12/12 11/11 14/14 14/15





68




TABLE 12

PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 3

--- ,, ' . .. .. .. J - - " - -- m lw ii - --i i- - - -
REPLICATIONS
Treatments I II III

endrin 10/14 4/14 10/14 diazinon 13/16 4/14 14/16 Bayer 25141 10/16 4/14 2/16 dimethoate 2/16 2/16 0/14 check 0/16 0/15 0/16 endrin 15/16 12/14 8/10 diazinon 11/14 7/10 14/16

H Bayer 25141 7/16 4/12 8/16

dimethoate 5/16 2/16 7/16 check 0/14 0/10 0/16 endrin 8/14 10/19 11/14 diazinon 5/16 8/15 16/18 Bayer 25141 10/14 14/17 8/17 dimethoate 1/19 1/19 2/15 check 0/15 0/16 0/18 endrin 10/15 10/13 13/16 diazinon 12/16 15/17 12/22 Bayer 25141 14/17 11/18 13/17

I dimethoate 8/15 8/18 1/17

check 0/16 0/19 0/15





69





TABLE 13

PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 4



REPLICATIONS
Treatments I II III

1. azinphosmethyl 4/16 12/15 8/12 2. endosulfan 3/10 0/11 4/10 3. Bidrin 0.5 lbs. 6/11 8/11 8/11 4. ethion 2/10 0/10 4/18 5. heptachlor 6/10 10/10 7/10 6. dimethoate 8/11 1/10 3/10 7. Bayer 39007 9/9 6/11 8/11 8. Kepone 2/11 2/11 2/12 9. G.C. 6506 0.25 lbs. 7/10 11/11 8/10 10. endrin 10/10 7/10 9/12 11. diazinon 8/9 8/9 9/10 12. Bayer. 25141 9/10 8/9 8/9 13. Bidrin 1.0 lb. 9/9 10/11 9/10 14. trichlorfon 1/11 4/8 :4/10 15. check 1/11 0/9 0/10 16. disulfoton 3/9 0/10 2/10 17. G.C. 6506 0.5 lbs. 5/10 12/14 8/9





70







TABLE 14

PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 5



REPLICATIONS
Treatments I II III IV

1. diazinon 8/14 6/18 2/18 2/12 2. Bayer 25141 10/12 18/18 10/12 4/10 3. check 2/20 4/20 0/20 6/22

4. G.C. 6506 12/14 18/20 6/6 2/2

5. Bidrin 6/12 12/16 10/18 6/14 6. Bayer 39007 12/20 6/20 4/20 10/20 7. endrin 10/20 6/18 18/20 14/20












BIOGRAPHICAL SKETCH


Jose R. Calvo was born February 24, 1929, at Cartago, Costa Rica. He obtained his elementary and secondary education at Cartago, Costa Rica, and was graduated from Colegio San Luis Gonzaga in February 1949. In February 1953 he received the degree of Agronomist from the Escuela Agricola Panamericana in Honduras. He taught field crops at the Tropical School of Agriculture in Daule, Ecuador until April 1954. In June 1956 he received the degree of Bachelor of Science from the University of Florida and went to head the Department of Agronomy of the National School of Agriculture of El Salvador. In 1959 he enrolled in the Graduate School of the University of Florida and received the degree of Master of Agriculture in June 1960, when he resumed his position at the National School of Agriculture of El Salvador. In 1962 he was appointed assistant professor in the Department of Agronomy of the Escuela Agricola Panamericana in Honduras. From September 1963 until the present time he has pursued his work toward the degree of Doctor of Philosophy.

Jose R. Calvo is married to the former Rhina Samayoa and is the father of three children. He is a member of the Entomological Society of America, the Florida Entomological Society, Pi Sigma, Alpha Tau Alpha, and Alpha Zeta.









71












This dissertation was prepared under the direction of the chairman of the candidate's supervisory committee and has been approved by all members of that committee. It was submitted to the Dean of the College of Agriculture and to the Graduate Council, and was approved as partial fulfillment of the requirements for the degree of Doctor of Philosophy.


April 23, 1966 Dean, College of Agriculture Dean, Graduate School SUPERVISORY COMMITTEE:









Airman


-Lc)R1~~c~ee




Full Text

PAGE 1

THE LESSER CORNSTALK BORER Elasmopalpus lignosellus (Zeller), AND ITS CONTROL By JOSfi R. CALVO A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA April, 1966

PAGE 2

ACKNOWLEDGMENTS The author expresses his appreciation to Dr. John T. Creighton for his interest and help in the conduct of this work, and for serving as chairman of his supervisory committee. He is grateful to Dr. A. N. Tissot, Dr. L. C. Kuitert, Dr. V. G. Perry, and Dr. 0. C. Ruelke for their confidence and understanding as members of the supervisory committee, and for reviewing the manuscript. Gratitude is expressed to Dr. L. C. Kuitert and Dr. D. H. Habeck, and to fellow graduate students Karl J. Stone, C. C. Russell, W. Yearian and J. F. Matta for their encouragement and assistance during the course of this investigation. Appreciation is expressed to Mrs. R. L. Linkfield and Dr. A. N. Tissot for their guidance in the preparation of the manuscript. Thanks are extended to the Organization of American States, Dr. W. G. Eden, Chairman of the Department of Entomology, and Colonel G. A. Farris, Adviser to Foreign Students, for financial aid. ii

PAGE 3

TABLE OF CONTENTS ACKNOWLEDGMENTS it LIST OF TABLES lv LIST OF FIGURES vi INTRODUCTION 1 REVIEW OF LITERATURE 3 Systematic History and Synonymy /J Seasonal Occurrence (J Cultural Control 6 Chemical Control 9 Biological Control 13 Diets 14 MATERIALS AND METHODS 15 Rearing Phase 15 Control Phase 21 RESULTS AND DISCUSSION 33 Rearing Phase 33 Control Phase 38 SUMMARY AND CONCLUSIONS 59 LITERATURE CITED 62 APPENDIX . 65 BIOGRAPHICAL SKETCH 71 iii

PAGE 4

LIST OF TABLES Table Page 1 Analysis of variance of corn plants surviving lesser cornstalk borer attack after insecticide treatments in Experiment No. 1 41 2 Evaluation of insecticides of Experiment No. 1 applied at 1 lb. of actual toxicant/acre to control lesser cornstalk borer larvae in corn seedlings 42 3 Analysis of variance of corn plants surviving repeated larval infestation after insecticide treatments in Experiment No. 2 44 v 4. Evaluation of residual effect of insecticides in Experiment No. 2 applied at 1 lb. /acre of actual toxicant to prevent infestation of lesser cornstalk borer on corn seedlings ... 45 5 Analysis of variance of corn plants surviving lesser cornstalk borer attack in light and heavy soils after liquid and granular insecticidal treatments in Experiment No. 3. . . 47 6 Analysis of variance of corn plants surviving lesser cornstalk borer attack after seed treatments with insecticides of Experiment No. 4 53 7 Evaluation of insecticides of Experiment No. 4, used as seed treatments on Dixie 18 corn against infestation of lesser cornstalk borer 54 8 Analysis of variance of corn plants surviving repeated larval infestation after seed treatment with insecticides of Experiment No. 5 56 9 Evaluation of residual effect of insecticides of Experiment No. 5 used as seed treatments on Dixie 18 corn, against repeated infestation with lesser cornstalk borer larvae ... 57 10 Proportions of surviving corn plants from individual plots of Experiment No. 1 66 11 Proportions of surviving corn plants from individual plots of Experiment No. 2 67 12 Proportions of surviving corn plants from individual plots of Experiment No. 3 68 iv

PAGE 5

LIST OF TABLES (Continued) Table Page 13 Proportions of surviving corn plants from individual plots of Experiment No. 4 69 14 Proportions of surviving corn plants from individual plots of Experiment No. 5 70 v

PAGE 6

LIST OF FIGURES Figure Page 1 Rearing cage on greenhouse bench 16 2 Cages for mating and oviposition in bioclimatic chamber . . 20 3 Adult male and female lesser cornstalk borer 22 4 Larvae in different instars 23 5 Infested corn seedling showing larva and silk tunnel. ... 24 6 Pupae; the pupa to the right shows the lack of sclerotization appearing after repeated artificial rearing 25 7 Open cocoon showing the pupa 26 8 Seedlings infested with eggs on paper strips 27 9 Mean percentages of surviving corn plants after insectiside treatments against lesser cornstalk borer infestation in Experiment No. 1 40 10 Mean percentages of surviving corn plants after preventive insecticidal treatments to test residual effect in Experiment No. 2 43 11 Lines showing the highly significant interaction between • soils and insecticides in Experiment No. 3 48 12 Lines showing the significant interaction between formulation and insecticides in Experiment No. 3 49 13 Mean percentages of corn plants surviving lesser cornstalk borer infestation after insecticide treatments of Experiment No. 3 50 14 Mean percentages of corn plants surviving lesser cornstalk borer infestation after insecticide seed treatments of Experiment No. 4 52 15 Mean percentages of corn plants surviving repeated infestation with lesser cornstalk borer larvae after insecticide seed treatments of Experiment No. 5 55 vi

PAGE 7

INTRODUCTION The lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), is a small moth of the family Phycitidae, subfamily Phycitinae. The larva is a pest of corn, field beans, peanuts, cowpeas, sugar cane, and wheat, particularly in the seedling stages. This insect is distributed throughout the Western Hemisphere from southern United States to Argentina, and is of special economic importance in areas of light soils, and during dry periods. Infestations are sporadic, 7 -! ) usually affecting the later plantings.^ The larvae bore into the seedlings Just below the soil surface, and tunnel upward into the stalk. From the entrance hole there extends into the soil a tube of silk and sand into which the larva withdraws when it is not feeding or when molested. Affected plants show signs of wilting in the bud leaves and die in a few days. Corn plants attacked in later stages are susceptible to lodging. This insect has been known as an agricultural pest in the United States since 1878. By 1903 it had become a serious pest of the above mentioned crops in southern United States. Because of the subterranean habitat of the larva, and the fact that it appears sporadically, this insect has often been overlooked as a pest, j its damage attributed to other causes. Surveys in the Gainesville area / in the springs of 1964 and 1965 showed some infested corn fields with about 20 percent of the plants attacked. Late corn plantings in the Pacific coastal areas of Central America are invariably affected by the 1

PAGE 8

2 pest, with considerable reduction in stand. Control of the lesser cornstalk borer is reported as impossible once the larvae are inside the plants. Thus, recommended control measures rely on prevention by cultural or chemical methods when the presence of the pest is suspected. The present work was undertaken to try to find methods of control which would not rely on prevention. Because natural infestations are sporadic and spotty, they do not provide satisfactory samples for field "> plot control experiments. Therefore, it was decided to mass-rear the in1 sect, and to artificially infest the experimental plants to be sure mean-/ ingful data would be obtained. Since laboratory rearing limited larval numbers, and because of the impossibility of controlling excessive soil moisture and natural enemies in the field, the control trials were conducted in the greenhouse.

PAGE 9

REVIEW OF LITERATURE C. V. Riley (1881) reported Elasmopalpus lignosellus (Zeller), as an agricultural pest injuring corn near Augusta, Georgia. Studies at that time showed that the insect had not been known as a pest until about 1878. Luginbill and Ainslie (1917) completed the study of its life cycle, begun by Riley in 1881. Sanchez (1960) worked out the life cycle of the insect in Texas, and his observations and measurements coincide with those presented by Luginbill and Ainslie (1917). These last authors also reviewed the literature on the lesser cornstalk borer through 1917. Systematic History and Synonymy As reported by Luginbill and Ainslie (1917), the species was first described by Zeller as Pempelia lignosella in 1848, from material obtained from Brasil and Uruguay, and a single female from "Carolina," United States. In 1852 Blanchard redescribed the species as Elasmopalpus angustellus , erecting the genus Elasmopalpus which is now the accepted position for the species. In 1872 Zeller recorded it from Brasil, Colombia, "Carolina," and Texas, and added the descriptions of two varieties, incautella and tartarella , based on color variations. Each of these varieties was described from a single specimen, and both were taken at the same place on the same date. The species is extremely variable and Zeller in 1881 placed incautella as a symomyn of lianosella and retained tartar ella as a valid variety. In 1874 Zeller described what he called "variety B" from material collected in Valparaiso, Chile. Berg in 1875 sup3

PAGE 10

4 plemented Blanchard's description of Elasmopalpus angustellus using material from Patagonia and other places in South America. He described venation in detail, and in 1877 concluded that Blanchard's angustellus was Zeller's lignosella . and that since both species were genotypes, the reduction of angustellus to a synonym of lignosella made Elasmopalpus a synonym of Pempelia . (According to Neave (1940) the genus Pempelia was erected by Huebner in 1825.) Zeller in 1881 published some notes on species variation based on 25 specimens from Colombia, South America. In 1888 Hulst redescribed the species as Dasypyga carbonella . In 1890 he rectified this and placed carbonella as a synonym of Zeller's variety tartarella . In the same publication he redescribed lignosellus and placed it in the genus Elasmopalpus for the first time, giving a bibliography and notes on the distribution and seasonal occurrence. In 1893 Ragonot published on the synonymy and bibliography, and gave a description of the species, calling attention to its great variability. He also used the name major , the first word in Zeller's description, for "variety B", and listed it as a variety of the species lignosellus . Smith in 1900 recorded the species for New York, and Dyar in 1902 listed it with synonyms, stating that it is distributed in the Atlantic States and South America. Ainslie (1917) came to the conclusion that the use of varietal names in this species could be discontinued. The varieties described are not constant in any respect, and apparently indicate individual aberrations in color, size, or markings. The synonymy then is reported as follows :

PAGE 11

Pempelia lignosella Zeller 1848 Elasmopalpus angustellus Blanchard 1852 Pempelia lignosella tartarella Zeller 1872 Pempelia lignosella incautella Zeller 1872 Dasypyga carbonella Hulst 1888 Elasmopalpus lignosellus (Zeller) Hulst 1890 Elasmopalpus lignosellus incautellus (Zeller) Hulst 1890 Elasmopalpus lignosellus tartarellus (Zeller) Hulst 1890 Heinrich (1956) reported the following synonymy: Elasmopalpus lignosellus (Zeller) Pempelia lignosella Zeller 1848 Elasmopalpus angustellus Blanchard 1852 Pempelia lignosella tartarella Zeller 1872 Pempelia lignosella incautella Zeller 1872 Pempelia lignosella malor Zeller 1874 Elasmopalpus anthracellus Ragonot 1888 Dasypyga carbonella Hulst 1888 Elasmopalpus lignosellus (Zeller) Ragonot 1889 Elasmopalpus puer Dyar 1919 (new synonymy). Seasonal Occurrence The occurrence of four generations a year in the latitude of Columbia, South Carolina, was suggested by Luginbill and Ainslie (1917), who also stated their belief that at that latitude the insect passes the early part of the winter in the larval stage, and the latter part as . pupae, and possibly adults. They also reported that the species

PAGE 12

6 probably overwinters in the larval stage in Arizona. The Quarterly Bulletin of the Mississippi Plant Board (1927) reports four generations a year, each taking from five to seven weeks, and states that the insect hibernates in the pupal stage in the soil. Vorhies and Wehrle (1946) reported that three generations occur in Arizona in a year, and that the insect probably overwinters in the soil in the larval stage. Harding (1960) observed that as a pest of peanuts in Texas this insect is a problem only in the fall, and that injury occurs about two weeks after plant emergence, and continues until harvest. Sanchez (1960), also working in Texas, suggested that the overwintering stage apparently varies from one area to another, depending on winter severity. The seasonal infestation of southern peas at Experiment, Georgia, was illustrated graphically by Dupree (1964). Infestation starts at under 1 percent before June 1, climbs to 5 percent on July 15, reaches a peak of 17 percent on August 15, and ends the first week of September. These percentages were the averages of five years. Cultural Control Luginbill and Ainslie (1917) recommended late fall or early winter plowing after freeing the fields from all crop residues as the best practice for preventing infestation. They also recommended disking field borders and terraces to stir the ground and break up the winter quarters of the pupae, and fertilization of sandy areas to stimulate growth and make plants more resistant. Early planting of corn and sorghum was

PAGE 13

suggested to enable the plants to get a good start before heavy infestation occurs. Cowan and Dempsey (1949) recommended thorough ground preparation to prevent borer damage to pimiento in Georgia. An apparent correlation between crop residues in the field before planting and the degree of infestation was observed by Is ley and Miner (1944). They suggested inspection of underground stems of food plants before planting to determine whether a thorough soil preparation was / necessary in order to kill half grown larvae. They believed that larvae' from eggs deposited after planting would not have time to develop to \ destructive size before the plants passed the most susceptible stage of / growth. This view was shared by Reynolds et al. (1959), Wilson and ICelf sheimer (1955), and Dupree (1964). The last author also stated that plowing under natural food and immediately planting a crop often results in concentrated feeding by the borer on the emerging plants. Dupree (1964) in a 1959 experiment combining cultural practices and chemical control, kept land free of weed growth by tillage prior to summer planting of southern peas. This resulted in control of lesser cornstalk borer superior to that obtained with insecticides. Is ley and Miner (1944) indicated that partial destruction of weed hosts hastens larval migration to the new crop and Reynolds et al. (1959) considered that cultivating out all infested hosts can be disastrous as it forces virtually the entire resident borer population to feed on the crop seedlings. Box (1929) recommended eradication of barnyardgrass Echinochloa crusgalli from iugc-r cane fields in Cuba as a method of control. Stahl (1930) attributed infestations on strawberries to grass weeds in the beds.

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8 Isley and Miner (1944) found that infestation of autumn beans in Arkansas in 1943 occurred following a spring crop of beans and a heavy growth of crabgrass Digitaria spp. Dupree (1964) indicated that planting legumes after plowing weedy small grain stubble promoted an ideal situation for borer damage to cowpea seedlings in Georgia. In the Quarterly Bulletin of the Mississippi Plant Board (1927) it is reported that cowpeas and soybeans are more subject to attack following plantings of corn. Plank (1928) reported from Cuba that burning trash after harvest of sugar cane favors infestation because' the trash prevents growth of wild hosts in the field. This was confirmed by Ingram et al. (1939) in Louisiana. On the other hand, Hayward (1943) recommended clean cultivation and manuring of sugar cane in Tucuman, Argentina, to prevent infestation. Stuckey (1945), and Bissell and Dupree (1947) reported a 2/3 reduction of infested cowpea plants when nitrogen, phosphorus, and potassium fertilizer was used, as compared to non-fertilized plots. Pulling and destroying all infested crop plants was recommended by Watson (1917) and Lauderdale (1920). Reynolds et al. (1959) used flood irrigation to control infestations on sorghum in California. The Report of the Puerto Rico Experiment Station (1937) mentions that small seeced bush-type varieties of lima beans show some resistance to the borer.

PAGE 15

Chemical Control Literature on the use of chemical insecticides against the lesser cornstalk borer is not abundant, and the work reported describes preventive insecticidal treatments rather than control of infestations. Isley and Miner (1944) obtained unsatisfactory control with applications of calcium arsenate and cryolite to the lower surfaces of the leaves and to the stems of bean plants against migrating la rvae in Kansas. Willie (1942) tried 3 percent DDT dust and 4 percent benzene hexachloride, corresponding tc 0.4 percent gamma isomer on beans in Peru, and reported that benzene hexachloride gave complete control of the larvae in a week. Dugas et al. (1948) in Louisiana, obtained perfect stands of corn in soils treated with 1 lb. parathion, 1.5 lbs. lindane, or 2.5 lbs. of chlordane per acre, each of which was much more effective than DDT. Kulash (1948), in North Carolina, obtained some control on snap beans with 3 percent lindane plus 5 percent DDT dust at the rate of 10 lbs. per acre, and with 60 grams of 50 percent DDT wettable powder in one gallon of water per 50 feet of crop row, applied to the base of the plants. This author reports between 30 and 40 percent control, by sampling enough plants to observe 10 larvae per treatment. Reduction of damage to sweet corn and green corn with early applications of DDT and chlordane was obtained in Florida by Kelsheioer et al.(1950), who concluded that no satisfactory control is known for this insect. Hills et al.(1953) confirmed that satisfactory control procedures for the lesser cornstalk borer have not been worked out, and reported reduction of damage to bush snap beans in Florida with applications of 2 lbs. per acre of parathion wettable powder in 100 gal. of water. The

PAGE 16

10 spray was applied to the base of the stems before cultivation which might cover the silk tunnels with soil, thus protecting the larvae from k the chemical. Hyche and Eden (1954) obtained control of this pest on cow peas in Alabama with 1 lb. endrin per acre, applied to the rows as a spray or broadcast as granules, at the time of plant emergence, with two subsequent applications at weekly intervals. Wilson and Kelsheimer (1955) reduced damage to cowpeas in Florida with 5 percent chlordane at the rate of 25 lbs. per acre applied to the rows just before the seedlings emerged. The same authors pointed out that the borers cannot be reached $ with insecticides after they enter the plants. Reduced damage to peanuts in Alabama was obtained with the use of 2.5 percent DDT or 10 percent toxaphene for control of leaf-feeding insects. Dust applications of DDT, benzene hexachloride, chlordane, toxaphene and aldrin in the drill at the time of sowing reduced damage to ) peanuts, but yields did not increase significantly. Similar treatments / in emulsion form did not reduce damage. Treatments with granular aldrin and dieldrin at the rate of 2 lbs. per acre, and with toxaphene at 6 lbs. per acre, were applied to the soil surface at the time the pods began to reach the soil; this resulted in reduced damage and increased yields significantly. All these treatments were applied against several insect pests of peanuts, including the lesser cornstalk borer, Arthur and Arant (1956). Reynolds et al. (1957) tried seed treatments on sorghum and soybeans with phorate and disulfoton at the rate of 1 lb. to 25 lbs. of seed, and by drilling 2 percent granules of both materials with the sorghum seed at the rate of 1 lb. of technical material per acre. Seed germination and

PAGE 17

11 stand of both crops were severely affected by the treatments, and little or no reduction of borer infestation was obtained. Falanghe (1958) applied 20 percent toxaphene dust, and 0.4 percent parathion at the rate of 12 lbs. per acre of wheat, followed by a low volume spray of 0.25 percent methyl demeton, or this spray alone. Both treatments improved the appearance of the plants and increased yields significantly. Successful control, according to Reynolds et al. (1959), depends on preventive applications of chemical insecticides. They reported control with endrin, aldrin, heptachlor, and dieldrin. These insecticides were applied in spray and granular form at the time of plant emergence on sorghum planted in seed beds 40 inches apart; no control was obtained, how) chemicals were applied at the rate of eight ounces per acre in concentrated bands. These authors hold that insecticides are ineffective after the larvae have become established in the plants. Cunningham et al. (1959) tried endrin treatments at the rate of 0.4 lbs. per acre in 20, 40, and 86 gallons of water applied to the base of peanut plants at monthly intervals to coincide with successive generations of moths, as determined by Sanchez (1960) in that area, and at intervals of 7, 14, and 21 days. There was a significant reduction of injury in all cases. Harding (1960) obtained chemical control with granular applications of 2 lbs. per acre of DDT, or 1 lb. per acre of disulfoton, parathion, phorate, or dieldrin. Sprays of 0.5 lbs. of endrin, parathion, azinphosmethyl, or isobenzan; 0.75 lbs. per acre of endosulfan, or 1 lb. per acre ever, when the seeds were planted flat and at closer distances. The

PAGE 18

12 of DDT, in five to ten gallons of water were the most effective materials tested; however, their residual effects were limited by the sprinkler irrigation used. These treatments were applied to the base of the plants at the time of moth emergence. Sanchez (1960) conducted control experiments on peanuts with DDT, endrin, demeton, azinphosmethyl, mevinphos, and Chlorothion (0, 0-dimethyl 0(3-chloro-4-nitrophenyl) thiophosphate) sprays; and with dust applications of endrin, dieldrin, heptachlor, DDT, and toxaphene. None of these treatments gave significant control. Dupree (1964) conducted a series of control experiments on legumes in Spalding County, Georgia, from 1959 to 1964. In one test he tried granular applications of 5 percent DDT, and 20 percent toxaphene at the rate of 5 lbs. per acre; 2.5 percent heptachlor at 0.5 and 2 lbs. per acre; 2 percent and 5 percent aldrin at 2 lbs. per acre; and 5 percent dieldrin at 2 lbs. per acre. These were protective treatments on southern pea seedlings, and all showed significant reduction in the number of dead plants. In another test 2.5 percent heptachlor, disulfoton, AC 528 (2,3-p-dioxanedithiol S,S-bis(0, 0-diethyl phosphorodithioate), and azinphosmethyl, at rates of 2, 1.5, 0.5, and 0.5 lbs per acre respectively; and 5 percent dieldrin at 0.5 lbs. per acre, all in granular form were tried. Heptachlor and disulfoton gave significantly more effective control. Granules of 5 percent aldrin at 8 lbs. per acre, and 2.5 percent heptachlor at 16 lbs. per acre were compared with Bacillus thuringiensis (Thuricide Dust 10 D) at 20 lbs. per acre. Both aldrin and heptachlor were more effective than the bacterium. In another test granular applica-

PAGE 19

13 tions of 5 percent aldrin and 2.5 percent heptachlor at the rate of 0.4 lbs. per acre; and 10 percent benzene hexachloride and DDT at the rates of 0.6 lbs. and 1 lb. per acre respectively were tried under conditions of clean and weed-fallow cultivation. Clean-fallow cultivation prior to summer planting of cowpeas resulted in control superior to that obtained from insecticides, although the insecticides were beneficial in reducing losses in the absence of this cultural practice. An experiment with dust applications of 0.3 lbs. per acre of dieldrin, 4 lbs. per acre of toxaphene, 2 lbs. per acre of DDT, 0.5 lbs. per acre of heptachlor, and 0.4 lbs. per acre of endrin gave no significant stand protection. Sprays with emulsions of aldrin at 0.5 lbs. per acre; methoxychlor, at 1 lb. per acre endrin at 0.5 lbs. per acre; and trichlorfon wettable powder at 0.5 lbs. per acre, in 77 gallons of water, gave significant reduction of damage for aldrin. These same treatments, plus dieldrin emulsion at 0.5 lbs. per acre in 300 gallons of water, gave significant reduction of damage for aldrin and endrin. Another experiment with emulsion treatments of aldrin, lindane, and heptachlor at 2 lbs. per acre, dieldrin at 1 lb. per acre, and endrin, mevinphos, and endosulfan at 0.5 lbs. per acre in 300 gallons of water applied to a 5 inch band at planting time, gave no significant differences for treatments. BioloRical Control Luginbill and Ainslie (1917) believed that the lesser cornstalk borer suffers very little from natural enemies due to the excellent protection afforded the larvae by feeding burrows and silk tubes. Leuck and Dupree (1965) listed the currently identified insect parasites of the

PAGE 20

14 borer and their abundance in the Piedmont and Coastal Plain regions of Georgia, and stated that parasitism is a contributing factor to the population variations which make this insect a sporadic pest. They reported the following parasites: On the eggs: 1. Telenomus (Telenomus ) n. sp. (Scelionidae, Hymenoptera) 2. Chelonus (Microchelonus ) n. sp. (Braconidae, Hymenoptera) On the larvae: 1. Pristomerus pacif icus melleus Cushman (Ichneumonidae, Hymenoptera) 2. Orgilus n. sp. (Braconidae, Hymenoptera) 3. Bracon mellitor Say (Braconidae, Hymenoptera) 4. Stomatomyia f loridensis Townsend (Tachinidae, Diptera) 5. Plagiprospherysa parvipalpis (Wulp) (Tachinidae, Diptera) Parasitism in different samples of larvae collected from soybeans and cowpeas during July and August fluctuated between 35 and 60 percent, with S. f loridensis being the dominant species, followed by Orgilus n. sp. and P_. pacif icus melleus . Leuck (personal communication) has since added Pristomerus pacificus appalachianus Viereck (Ichneumonidae, Hymenoptera) to this list. l£ ' Diets The diet recommended by Berger (1963) for rearing larvae of Helio this species was adopted for rearing lesser cornstalk borer larvae. This diet is described on page 18 under Material and Methods.

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MATERIALS AND METHODS This study was conducted from May, 1964 to October, 1965, and consisted of two phases: 1. the establishment of a laboratory population; 2. control experiments conducted in the greenhouse. The laboratory population was necessary because suitable samples could not be obtained from natural infestations due to the sporadic nature of the pest. Rearing Phase Lesser cornstalk borer larvae were collected in May, 1964, from corn seedlings in the Gainesville, Florida, area. They were transferred inside their sand tubes to potted corn seedlings inside screen cages where they were reared to maturity. The moths were then fed a 10 percent solution of honey in water. The rearing cages measured 25 x 15 x 15 inches. Pieces of cellucotton or paper towel were provided for oviposition. To supplement the small population obtained from field collected larvae, two ultraviolet light traps were run throughout the period, and adults were collected from the middle of July to September, 1964, when the moths ceased to come to the traps. In order to rear a larger population than the potted seedlings allowed, a large screen cage was built over a greenhouse bench (Figure 1). This cage was 12 x 3 x 2 feet, and was provided with three cloth sleeves for access. A sliding panel left 3/4 of the space as a nursery where the tissue strips with the attached eggs were placed on closely planted corn seedlings. The remaining 1/4 of the space was used for concentration and collection of the adults, which were attracted to it by a light, 15

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16 Figure 1. Rearing cage on greenhouse bench.

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17 and collected in this compartment by pushing in the sliding panel and picking them up with a shell vial. The adults were then transferred to screen cages 9x9x5 inches in size, where mating and oviposition took place. These cages, on stilts, were placed on water pans to prevent ants from preying on the eggs. The adults were fed 10 percent honey in water, with 1 gram of sorbic acid added per 500 cc of diet to prevent mold. The eggs were laid on paper towels placed on top of the cages . The following artificial diets were tried when it became evident that a population sufficiently large to carry out infestation of the experimental plants could not be obtained from the greenhouse rearing: 1. Macerated corn seedlings in agar, with methyl p-hydroxybenzoate and sorbic acid as preservatives, tried with and without the fiber, and in different proportions of agar and water. 2. A diet consisting of the following ingredients devised by W. Yearian, a fellow graduate student at the University of Florida: 1. macerated corn 100 g 2. water 300 cc 3. agar 12 g 4. sucrose 5 g 5. fructose 5 g 6. vitamin fortification mixture 2 g 7. soybean protein 10 g 8. peanut oil 1 C c

PAGE 24

18 9. cholesterol 0.5 S 10. Wesson's salts 1.0 S 11. yeast 5.0 g 12. choline chloride 0.1 g 13. glycine 15.0 g 14. cysteine 15.0 g 15. tegosept 0.5 S 16. sorbic acid 0.5 g The following diet recommended by Berger (1963) for rearing larvae of Heliothis species was adopted for rearing lesser cornstalk borer larvae: 1. distilled water 208.5 cc 2. 22.5 percent KOH 4.3 cc 3. casein 29.2 g 4. Wesson's salts 8.5 g 5. sucrose 22.7 g 6. 10 percent formaldehide 3.1 cc 7. Mixture of: 7 g methyl p-hydroxybenzoate + 7 g sorbic acid in 50 cc of 95 percent ethyl alcohol 12.5 cc 8. wheat gern 25.6 g 9. alphacel 4.3 g 10. vitamin fortification mixture 8.5 g 11. agar, hot, dissolved in 521 cc of water 21.3 g 12. ascorbic acid 3.4 g 13. streptomycin sulfate (700 micrograms/ml.) 118.0 mg

PAGE 25

19 These diets were placed in petri dishes, on sterilized sand in mason jars; or in shell vials 19 mm in diameter and 7 cms in height. Pieces of paper towel with eggs attached were placed on or near the diet, or newly hatched larvae were placed on the diet using a camel hair brush. Rearing in the shell vials on the wheat germ base diet (Berger 1963) was finally adopted because preliminary trials showed this to be the best. The diet was prepared in a blender. Approximately 5 cc of the freshly mixed warm diet were placed in each sterilized vial with a plastic dispenser bottle. Then the pieces of paper towel with one to several eggs were placed in the vials, without contact with the diet, and held in place with a cotton plug. The vials were then kept in drawers, under each of which a 60 watt electric bulb was placed to maintain the temperature at 30 to 35°C. A glass container with water in each drawer prevented drying of the diet. The larvae completed development in about three weeks, and the pupae were removed from the vials with a metal hook and placed in Syracuse dishes which were then transferred to screen cages measuring 9x9x6 inches (Figure 2). These were kept in a bioclimatic chamber at 27°C, and 40 to 50 percent relative humidity, and with 14 hour periods of light. At emergence, the moths were fed the above mentioned honey in water diet. About seventy larvae were started each week in as many vials; a total of four hundred vials was used for this work. Observations were made on the number and size of larval instars and their duration in laboratory rearing. The number of eggs per female

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20 Figure 2. Cages for mating and oviposition in bioclimatic chamber .

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21 was estimated as indicated on page 35 under Results and Discussion. Photographs were taken of the insect in different stages of development (Figures 3, 4, 5, 6, and 7). Control Phase Dixie 18 corn seedlings were infested with eggs or larvae in different instars, Infestation from eggs was obtained by cutting the paper towels used for oviposition into small pieces, with at least two eggs on each; these paper pieces were glued to the stem when the seedlings were in the two leaves stage. Another method was to place a layer of dry soil at the base of the seedlings and sink the paper pieces with the eggs into the soil in contact with the stems (Figure 8). Third or fourth instar larvae were also used for infestation. A larva was extracted from the vial with a metal hook and placed on dry loose soil at the base of each seedling in contact with the stem. A half pint paper cup with the bottom removed was placed around each seedling to discourage the larvae from wandering away. The seeds were planted in rows on greenhouse benches, and bands of vaseline applied to the legs of the benches to keep predatory ants out. Soil moisture was kept at a minimum to favor infestation. Six experiments in control using chemical insecticides were conducted from July to November, 1965. Two greenhouses 20 x 15 feet were screened for this purpose. The common names of insecticides used in this work follow the designations given by Billings (1963 and 1965). The chemical names of proprietary compounds used follow; subsequent reference to these compounds

PAGE 28

Figure 3. Adult male and female lesser cornstalk borer.

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23 Figure 4. Larvae in different instars.

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24 Figure 5. Infested corn seedling showing larva and silk tunnel

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25 Figure 6. Pupae; the pupa to the right shows the lack of sclerotization appearing after repeated artificial rearing.

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Figure 7. Open cocoon showing the pupa.

PAGE 33

27

PAGE 34

28 will be by their proprietary names or code numbers: Bayer 25141 1 --0, 0-diethyl 0-p(methylsulf inyl) phenyl phosphorodithioate. Bayer 39007 1 --0-isopropoxyphenyl methylcarbamate. 2 Bidrin —dimethyl phosphate of 3-hydroxy-N,N-diraethyl-cis-crotonamide. G.C. 6506 3 --dimethyl p(methylthio) phenyl phosphate. 3 Kepone --decachlorooctahydro-1, 3,4-metheno-2H-cyclobuta [cd] pentalen-2one. Experiment No. 1 . The purpose of this experiment was to screen fifteen insecticides which appeared promising for control of the lesser cornstalk borer, either from reported effects in the prevention of this insect, or in control of similar pests. A greenhouse bench 33 inches wide and 5 inches deep was filled with Kanapaha fine sand and divided with plastic strips into 48 sections 9 inches wide and 33 inches long. On July 28, 1965, two rows of ten seed each of Dixie 18 corn were planted in each section, equidistant from each other and from the plastic walls. On August 4, when the seedlings were in the two leaves stage and about 3 inches high, paper strips with 3-day-old eggs were placed on them as described previously. By this method 100 percent infestation of the plants was obtained. The experiment was laid out in a completely randomized design with three replications per treatment and two seedling rows per replicate. On August 13, when about 10 percent of the seedlings had begun to show signs of infestation, and the larv ae were in the third and fourth ins tars, the following ^-Provided by Chemagro Corporation. 2 Provided by Shell Chemical Company. 3 Provided by Allied Chemical Corporation.

PAGE 35

29 ' -\ " » insecticides were applied at the rate of 1 lb. active material per acre in 50 gallons of water: Bayer 25141, Bayer 39007, Bidrin, diazinon, di1 1 9 methoate, disulfoton, trichlorfon, endrin,^ ethion, G. C. 6506, azinphosmethyl, heptachlor, 2 Kepone, phorate, and endosulfan. Bayer 39007, trichlorfon, and Kepone were used as wettable powders phorate was used in granular form since no liquid form or wettable powder was available. All the other insecticides were used in emulsion form. Th liquid applications were made with a plastic bottle and directed to the base of the plants. Phorate granules were applied in a narrow band at the base of the plants. At the time of treatment, and 15 days after treatment, the number of healthy plants per experimental unit was counted. Experiment No. 2. Four of the chemical insecticides which appeared most effective in experiment no. 1 were tried for residual effect in a completely randomized design with four replications. Each replicate consisted of two rows of ten seeds each of Dixie 18 corn planted in units of the same size as in experiment no. 1, and with the same distance between t] seed rows and the plastic walls limiting the unit. The seeds were planted on September 1, 1965, on Kanapaha fine sand, and treated on September 10, when at the two leaves stage, with the following insecticides in emulsion form applied to the base of the plants at the rate of 1 lb. of active material per acre in 50 gallons of water: Bayer 25141, diazinon, endrin, and G.C. 6506. •'Provided by Chemagro Corporation. 2 Provided by Velsicol Chemical Corporation.

PAGE 36

On September 15, when the plants were about six inches high, they were infested with one-fourth instar larva per plant. On September 25, when the plants were about 15 inches high, another fourth instar larva was placed on the soil at the base of each plant. Healthy living plants were counted on October 13. Experiment No. 3 . Four of the better performing insecticides from experiment no. 1, which were available in both granular and emulsifiable formulations were evaluated in a split-split plot design with three randomized blocks, using a heavy soil (Fellowship loamy fine sand), and a light soil (Kanapaha fine sand) as main plots; formulation as sub-plots; and insecticides as sub-sub-plots. The experimental units were similar to those described, except that the seedling rows were only 30 inches long. Dixie 18 corn seed was planted on September 10, 1965, and infested on September 18 with mature eggs. Plants in sandy soil showed signs of infestation first, and were treated on September 27. Those on clay soil were treated on October 4. Endrin, diazinon, Bayer 25141, and dimethoate were used in emulsion form at the rate of 1 lb. active material per acre, in 50 gallons of water, and in granular form at 2 lbs. active material per acre. Both the emulsion and granules were applied in narrow bands at the base of the plants. Healthy, living plants in sandy soil were counted on October 12, and those on clay soil on October 16.

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31 Experiment No. 4. The same group of insecticides, except phorate, used for control in experiment no. 1, were tried as seed treatments on Dixie 18 corn, at the rate of 1 lb. of technical material to 100 lbs. of seed, except G.C. 6506 used at 0.5 lbs/100 lbs. and Bidrin used at both 1 lb. and 0.5 lbs/100 lbs. of seed, following observations from preliminary trials. For each treatment 1 ounce of seed was placed in a 100 cc glass jar, and a pipette used to add the proper amount of the corresponding insecticide in emulsifiable concentrate, or wettable powder form. Twelve hours after being mixed with the chemical, the seed was planted in Kanapaha fine sand in a greenhouse bench. A completely randomized design was used, with three replications. The experimental units were similar to those of previously described experiments. The seed was planted on August 15, 1965, the seedlings were infested with eggs when at the two leaves stage, on August 24, anc the healthy living plants counted on September 10. Experiment No. 5 . This experiment was performed to study with more precision the effects as seed treatments, and the residual effects of some of the better performing chemicals from experiment no. 4. Dixie 18 corn seed from the 1964 harvest was used. The seed was treated with diazinon and Bayer 39007 at the rate of 0.75 lbs./lOO lbs, endrin, Bidrin, and Bayer 25141 at 0.5 lbs./lOO lbs, and with G.C. 6506 at 0.25 lbs./lOO lbs. It was found necessary to determine tolerable dosages of insecticides for the new seed. The seed was treated in the manner described for experiment no. 4, and planted in Zuber loamy fine sand on September 12, 1965, twelve hours

PAGE 38

32 after treatment. A completely randomized design with four replications was used; the experimental units had the same characteristics as those in former experiments. Paper strips with 3-day-old eggs were placed on the seedlings on September 18. On September 22 and again on September 30, one fourth instar larva was placed at the base of each plant. The proportions of healthy living plants were determined on October 10.

PAGE 39

RESULTS AND DISCUSSION Rearing Phase Rearing of the larvae in the wheat base diet (Berger 1963) was successfully carried out in shell vials; however, rearing on corn seedlings in the greenhouse was continued as a source of material in case of need. This greenhouse rearing had allowed observations on the development of larvae in corn seedlings, and served as a guide for infesting the experimental plants in chemical control trials, and for determining how much time could elapse between the appearance of signs of infestation and the treatment. Moreover, this greenhouse population showed the existence of many more males than females at the beginning and the end of the season, and also the fact that over -wintering occurred in the pupal stage and had diapause characteristics. The selected diet was prepared as described by Berger, 1963, poured in the shell vials, and kept under refrigeration until needed. At first, a sterilized camel hair brush was used to place a newly hatched larva in each vial. This procedure was later abandoned, for the more expedient one of cutting the paper towels used for oviposition into strips with one or more eggs on them, and placing these strips in the vials in such a manner as to avoid contact with the diet which inhibited hatching. Pupation occurred between 15 and 40 days after hatching, with most larvae pupating in about 22 days. Due to this variation in time, it was difficult to rear more than one larva per vial, as some of the pupae were preyed upon by slow developing larvae. 33

PAGE 40

34 The use of eggs on paper strips for rearing caused fungal contamination in some of the vials, making the diet unfit and causing the death of the larvae. The number of contaminated vials, however, was never large. The contaminating fungi were of the genera Rhyzopus and Aspergillus . The mite Tyrophagus putrescentiae (Schrank), which preyed on the eggs in the bioclimatic chamber, was also introduced into some of the rearing vials, where it proliferated abundantly and caused death of the larvae. Few vials were infested if the oviposition cages were withdrawn every 15 days from the chamber and cleaned, and the temperature in the chamber was raised to 60°C for 20 minutes before replacing the cages. This procedure also checked the saw-toothed grain beetle, Oryzaephilus surinamensis (L), and the cigarette beetle, Lasioderma serricorne (Fab.), which established populations in the ovipositing cages. Ants were kept out by placing the cages on a table with the legs in jars with water. A continuous population was maintained in this manner from June, 1964. After three successive generations were reared on the diet, a small percentage of the pupae appeared in which the wing pads were poorly developed, and there was a lack of sclerotization over the 3rd and 4th abdominal segments of the pupal case (Figure 6). At emergence the pupal case split across that poorly sclerotized area leaving a hood over the head and thorax from which the adults could not escape. Addition of 60 grams of macerated corn seedlings to 873 grams of diet eliminated this problem, making it unnecessary to replace the population. The use of sorbic acid in the honey in water fed to the adults made it possible to keep the diet for a week; during this time only water was added to the cotton wads previously saturated with the diet.

PAGE 41

35 Thirty-five newly emerged females and thirty-five males were placed in an oviposition cage in the bioclimatic chamber on August 5, 1965. An average of sixty-seven eggs per female was obtained; oviposition occurred as follows: August 8 156 eggs August 15 87 eggs August 9 255 eggs August 16 301 eggs August 10 340 eggs August 17 0 eggs August 11 462 eggs August 18 173 eggs August 12 458 eggs August 19 115 eggs August 13 0 eggs August 20 57 eggs August 14 12 eggs August 21 30 eggs The number of larval ins tars and their respective sizes were found to coincide with those reported by Luginbill and Ainslie (1917), and Sanchez (1960). Duration of these larval instars was approximately as reported by Luginbill and Ainslie (1917) for the months of September and October in Columbia, South Carolina. A large population of lesser cornstalk borers, needed for conducting research in chemical control, could not be established from larvae collected in the field because small numbers of adults were obtained, and no mating took place in the rearing cages unless there were about 10 moths per cubic foot, with equal proportions of both sexes. Mated females from light traps were collected in increasing numbers from June to September of 1964, but a working population could not be established because very few specimens were collected during humid periods. An abundance of eggs from females collected in light traps permitted rearing of a large popu-

PAGE 42

lation merely by placing eggs deposited on paper towels along the corn seedling rows growing in a screened greenhouse bench. This greatly improved rearing technique had two serious limitations: 1. It was impossible to have enough seedlings at all times to maintain a large, constant population, and fluctuations in the population size made the conduct of control experiments very difficult. 2. Extreme humidity in the second and third weeks of September 1964, which put an end to light trap collections of the insect, also considerably decreased the greenhouse population; oviposition diminished and most of the eggs did not hatch. By the end of September, 1964, emergence of adults in the greenhouse rearing cage ceased despite the fact that the temperature was maintained between 27°C and 32°C throughout the winter. Adults did emerge from pupae sifted out of the rearing cage sand and extracted from the cocoons; however, not enough of them were obtained to begin a population, because of the need to leave sufficient overwintering pupae to resume the rearing the following spring, in the event a population could not be carried through the winter. Another disadvantage of the greenhouse rearing was the constant need to control grease ants Monomorium pharaonis . which preyed on the eggs and larvae of the lesser cornstalk borer. This problem was solved, however, by the use of a Kepone peanut butter bait. In an effort to expedite the rearing operation, and to control the number of insects being reared, artificial diets were tried unsuccessfully in 1964. Although some partly grown larvae continued to develop in both macerated corn in agar, and in the Yearian diet described in materials and methods, most larvae failed to complete development. Newly hatched larvae could not be established on the first diet although several changes were

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37 made in it. Some larvae were reared on the second diet, but mortality was too high to justify its use over the rearing in corn seedlings. In the spring of 1965, rearing was resumed from adults emerging from overwintering pupae in the greenhouse rearing bench. Another source of the borer was found in a heavy infestation on experimental plots of Rhodesgrass Chloris gay ana , in Hague, Florida. Five hundred larvae were collected and brought to the greenhouse where development continued on corn seedlings. A later collection of two hundred larvae from the same source was reared to maturity on the wheat germ base diet (Berger 1963) by placing the diet on sterilized sand in glass jars 7 inches in diameter and 3 inches in height. These larvae were brought from the field in their sand tunnels, extracted with a Berlese funnel, and placed in the jars with the diet. About 20 percent of the last group of larvae were parasitized by Orgilus n. sp. (Braconidae, Hymenoptera) . Also three specimens of Pristomerus pacif icus melleus Cushman (Ichneumonidae, Hymenoptera) were recovered. These parasites were sent to the United States National Museum for identification. The glass jars used to rear field collected larvae in the wheat base diet (Berger 1963), were used to rear larvae from the first instar, but they were not satisfactory because contamination of the diet with fungi, primarily Rhyzopus nigricans , and Aspergillus sp. was almost unavoidable, and because slow developing larvae preyed on the pupae from faster growing larvae.

PAGE 44

Control Phase Eggs used to infest experimental plants hatched within 24 hours. First instar larvae buried under the dry layer of sand at the base of the plants after wandering about the stem; some larvae climbed to the leaves and fed there for a while before boring into the stems under the soil line. Some plants began to show signs of infestation about ten days after hatching of the eggs, when the larvae were in the fourth or fifth instar, but since only a small percentage of the larvae attained that stage of development in ten days, it was possible to obtain good control by treating within approximately three days of the appearance of signs of infestation. Affected plants showed wilting of the bud leaves. Stunting effects were not noticed up to the appearance of wilting. Some of the plants showing signs of infestation died, their number depending on the delay between the appearance of signs and treatment, and on the type of treatment. Many of these plants recovered with the treatment, but were counted as surviving only when they did not show signs of stunting. The experimental plants grew more slender, and less vigorous than they normally would have grown in the field, and probably were more susceptible to the attack of the borer. There was 100 percent infestation of the experimental plants, and in some experiments all control plants died. Infestation trials showed it was best to use third and fourth instar larvae. Younger larvae were hard to handle, and older ones were very restless, and wandered away from the seedling on which they were placed. Third or fourth instar larvae would immediately enter the soil around the stem and start building a tunnel. Seedlings attacked by mature larvae

PAGE 45

39 toppled in a few hours without showing any signs of infestation. Experiment No. 1. The mean percentage of surviving plants per treatment is presented in histogram form in Figure 9. An arcsine transformation was made on the proportions of surviving plants, and the transformations were submitted to analysis of variance (Table 1). Treatment effects were highly significant, and a Duncan's test was used to compare treatment means (Table 2). Treatments with Bayer 25141, G. C. 6506, diazinon, endrin, dimethoate, azinphosmethyl, trichlorfon, phorate, disulfoton, Bidrin, and Bayer 39007 gave highly significantly better control than the untreated plots. A highly significant difference was obtained between Bayer 25141 and Bayer 39007, the first being more effective. Experiment No. 2 . The four insecticides used were highly effective in preventing infestation by partially grown larvae, although each corn seedling was infested with mature larvae on two different dates. The mean percentages of surviving plants are presented in histogram form in Figure 10, which shows the small percentage of survival in the untreated plots. An arcsine transformation of the proportions of surviving plants was submitted to analysis of variance (Table 3). There were highly significant treatment effects; a Duncan's test for treatment means was performed (Table 4). G.C. 6506, endrin, Bayer 25141, and diazinon were all highly significantly better than the control, with no significant difference among them.

PAGE 46

Bayer 25141, 98.47. G.C. 6506, 92.07. diazinon, 89.6% endrin, 89.17. dimethoate, 86.47. azinphosmethyl, 81.37. trichlorfon, 74.17. phorate, 73.07. heptachlor, 71.27. disulfoton, 59.17. Bidrin, 50.17. Bayer, 39007, 35.87. ethion, 32.27. endosu fan, 21.07. Kepone, ( .37. check, 0.07. o o 00 o o o o o O CM — r O

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TABLE 1 ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING LESSER CORNSTALK BORER ATTACK AFTER INSECTICIDE TREATMENTS IN EXPERIMENT NO. 1 Source of Degrees of Sum of Mea n Variation Freedom Squares Square Total 47 31,041.45 Treatments 1 5 23,792.14 1,586.14** Error 32 7,249.31 226.54 ^Significance at the 17„ level.

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42 TABLE 2 EVALUATION OF INSECTICIDES OF EXPERIMENT NO. 1 APPLIED AT 1 LB. OF ACTUAL TOXICANT/ACRE TO CONTROL LESSER CORN STALK BORER LARVAE IN CORN SEEDLINGS Treatment Mean Surviving Plants Percent Arcs ine* 0 0 \j . \j U.00 a U.J 14.53 ab Li. mV 27.93 abc "*9 9 34.56 abed 1 5. ft 36.76 bed 45.06 bede Dy • ± 50.20 bede 71.2 57.53 cde 73.0 58.66 cde • 74.1 59.36 cde 81.3 64.43 de 86.4 68.40 de 89.1 70.73 de 89.6 71.23 de 92.0 73.43 de 98.4 82.66 e check Kepone endosulfan ethion Bayer 39007 Bidrin disulf oton heptachlor phorate trichlorfon azinphosmethyl dimethoate endrin diazinon G.C. 6506 Bayer 25141 Any two means followed by the same ent at the 1% level. Significance letter are not significantly differbased on Duncan's test.

PAGE 49

43 100 90 80 70 60 > u 3 (0 u a w C 0) u W > id M o ON s on o vO a Figure 10. Mean percentages of surviving corn plants after preventive insecticidal treatments to test residual effect in Experiment No. 2.

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TABLE 3 ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING REPEATED LARVAL INFESTATION AFTER INSECTICIDE TREATMENTS IN EXPERIMENT NO. 2 Source of Degrees of Sum of Mean Variation Freedom Squares Square Total 19 18,663.08 Treatments 4 16,080.57 4,020.14** Error 15 2,582.51 172.16 **Significance at the 1% level.

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TABLE 4 EVALUATION APPLIED AT OF RESIDUAL EFFECT OF INSECTICIDES IN EXPERIMENT NO. 2 1 LB. /ACRE OF ACTUAL TOXICANT TO PREVENT INFESTATION OF LESSER CORNSTALK BORER ON CORN SEEDLINGS Treatment Mean Surviving Plants Percent Arcsine* check 3.00 9.80 a diazinon 93.40 75.12 b 96.60 79.35 b endrin 97.00 79.90 b G.C. 6506 99.55 86.17 b *Any two means followed by the same letter are not significantly different at the 1% level. Significance based on Duncan's test.

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Experiment No. 3 . Treatments in this experiment were applied somewhat late for best results. Treatments on heavy soil were delayed because soil moisture was harder to keep at a minimum in this soil, and the plants did not show signs of infestation early enough. An arcsine transformation of the proportions of surviving plants was submitted to analysis of variance (Table 5). There was a highly significant interaction between soil and chemical insecticides (Figure 11). Endrin and diazinon gave the best control on both types of soil, whereas Bayer 25141 gave about the same level of control in heavy soil as did endrin and diazinon, but a much lower one in light soil. Dimethoate was poor in both soils. The interaction between formulation and chemical insecticides (Figure 12), was significant at the 5 percent level. The four chemicals gave better control in liquid application despite the fact that twice as much technical material was used in the granular applications. The histogram in figure 13 shows the mean percentage of surviving plants per treatment across the experiment. Experiment No. 4 . Several preliminary trials had to be made to determine the effect of the treatments on seed germination and stand, in order to determine the proper dosage. Dosages never exceeded 1 lb. of technical material per 100 lbs. of seed, because it was not possible to add more material with the procedure used. Plants from seed treated with G.C. 6506, Bayer 25141, and diazinon showed some signs of toxicity, but recovered in about 8 days and did not appear different from plants in other treatments.

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47 TABLE 5 ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING LESSER CORNSTALK BORER ATTACK IN LIGHT AND HEAVY SOILS AFTER LIQUID AND GRANULAR INSECTICIDAL TREATMENTS IN EXPERIMENT NO. 3 Source of Va ri flti on Degrees of jfreeaom Sum of Squares Mean Square MAIN PLOTS blocks 2 222.26 111.13 soil, S 1 113.70 113.70 error a 2 126.40 62.20 9TrR PT OTQ X Ui U1U X d L X UU j X X 1,195.37 1,195.37 SF 1 22.62 22.62 error b 4 814.75 203.68 SUBSUB PLOTS insecticides, I 4 29,783.87 7,445,96 SI 4 3,310.21 827.55** FI 4 630.88 157.72* SFI 4 99.54 24.88 error c 32 1,316.95 41.15 *Significance at the 57» level. ^Significance at the 1% level.

PAGE 54

48 100 90 80 70 cd > 60 > H 3 cq c a
PAGE 55

49 granular emulsion Figure 12. Lines showing the significant interaction between formulation and insecticides in Experiment No. 3. i

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50 100 90 80 70 60 50 40 30 20 10 5-S O o U a) JS u g o cnj ed o a O s •H If) m M 0) pq n oo 00 VD o d N t-l o c Figure 13. Mean percentages of corn plants surviving lesser cornstalk borer infestation after insecticide treatments of Experiment No. 3.

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51 Plants from seed treated with Bidrin looked more vigorous than those from untreated seed in this experiment. Figure 14 shows the mean percentage of plant survival per treatment. An arcsine transformation was made on the proportions of surviving plants, and the transformations submitted to analysis of variance (Table 6). There was a highly significant difference for treatments. A Duncan's test of comparisons among treatment means (Table 7) showed that Bidrin, Bayer 25141, diazinon, endrin, heptachlor, Bayer 39007, and azinphosmethyl at 1 lb./lOO lbs.; G.C. 6506 and Bidrin at 0.5 lbs./lOO lbs.; and G. C. 6506 at 0.25 lbs./lOO lbs. were highly significantly better than the check. These chemicals provided protection against larvae developing from egg infestations. Dimethoate, trichlorfon, Kepone, endosulfan, disulfoton, and ethion did not differ from the check at the 1 percent level. Experiment No. 5 . This experiment had to be repeated because germination was completely inhibited by seed treatments of Bayer 25141 at 1 lb./lOO lbs. and G.C. 6506 at 0.5 lbs./lOO lbs., and severely reduced by endrin at 1 lb./ 100 lbs. Dixie 18 corn seed of the 1965 crop was used, and germination trials had to be made to determine that B 25141, G.C. 6506, and endrin could be used safely at rates of 0.5, 0.25, and 0.5 lbs./lOO lbs. respectively. Figure 15 shows a histogram of mean percent plant survival per treatment. The analysis of variance of the transformed proportions is presented in Table 8. There was a highly significant difference for treatments, and a Duncan's test (Table 9) showed that endrin, Bayer 25141,

PAGE 58

Bidrin. 95.57. Bayer 25141, 89.0% diazinon, 89.07. G.C. 6506 (0.5 lbs.), 89.07. endrin, 87.17. heptachlor, 83.27. Bayer 39007, 82.67. o o oo o o G.C. 6506 (0.25 lbs.), 76.47. Bidrin, 66.57. azinphosmethyl, 57.3% dimethoat e, 35.3% trichlorfon, 31.57. Kepone, 17.77. endosulfan, 16.7% disulfoton, 12.3% ethion, 9.8% check 1.27. o o o CO o CN1

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TABLE 6 ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING LESSER CORNSTALK BORER ATTACK AFTER SEED TREATMENTS WITH INSECTICIDES OF EXPERIMENT NO. 4 Source of " Degrees of Sum of Variation Freedom Squares Total 50 33,351.46 Treatments 16 25.420.88 Error 34 7,930.58 Mean Square 1,588.80** 233.25 **Significance at the 1% level.

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54 TABLE 7 EVALUATION OF INSECTICIDES OF EXPERIMENT NO. 4, USED AS SEED TREATMENTS ON DIXIE 18 CORN AGAINST INFESTATION OF LESSER CORNSTALK BORER Treatment Mean Percent Surviving Plants Arcs ine* check 1 .20 A 1 O. a o . ij a ethion (1 lb./lOO lbs.) 9 .80 IS OC\ ok io . zu a d disulfoton " 12 .30 Ofl CO ak endosulfan " 16 .70 O/. 1 o . ij aoc Kepone " 17 .70 9A P.A ak« . oo a dc trichlorfon " 31 50 OA 1(1 _ 1_ _ j j't . aucd dimethoate " 0£ CO u ~ : Jo. 53 abed azinohosmethvl " 49.23 bede Bidrin fO 50 lbs /lfifi 1h«s aa c.n DO . jU 54.66 bede G.C. 6506 (0.25 lbs./lOO lbs.) 76.40 60.93 cde Bayer 39007 (1 lb./lOO lbs.) 82.60 65.33 de heptachlor " 83.20 65.83 de endrin " 87.10 68.93 de G.C. 6506 (0.50 lbs./lOO lbs.) 89.00 70.06 de diazinon (1 lb./lOO lbs.) 89.00 70.33 de Bayer 25141 89.00 70.63 de Bidrin 95.50 77.73 e *Any two means followed by the same ent at the 1% level. Significance letter are not significantly differbased on Duncan's test.

PAGE 61

55 G.C. 6506, 96.87. Bayer 25141, 82.3% endrin, 62.0% Bidrin, 60.0% Bayer 29007, 47.1% diazinon, >7.6% check, 10.7% o o o o oo o o NO o o o CO o i-t o c o a 0) w 6 CO 4J U Cfl ca ai •o 0) 0 ca 4J d a) 01 T3 Oi -H O o 4J 60 O C > ca u ca co C oi CO H > a m CO C »-l M O H U O) u <+-l o O .£> CO Js! cr> 0) »-< 60 CO • cfl -U O CO* h 4J O C 0) u M a a. u O 0) s 01 u C co o CO CO Oi aj ai x cu 3 60 S-l

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TABLE 8 ANALYSIS OF VARIANCE OF CORN PLANTS SURVIVING REPEATED LARVAL INFESTATION AFTER SEED TREATMENT WITH INSECTICIDES OF EXPERIMENT NO. 5 Source of Degrees of Sum of Mean Variation Freedom Squares Square Total 27 13,905.53 Treatments 6 9.738.21 1,623.03** Error 21 4,167.32 198.44 **Significance at the 1% level.

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57 TABLE 9 EVALUATION OF RESIDUAL EFFECT OF INSECTICIDES OF EXPERIMENT NO. 5 USED AS SEED TREATMENTS ON DIXIE 18 CORN, AGAINST REPEATED INFESTATION WITH LESSER CORNSTALK BORER LARVAE Mean Surviving Plants Treatment Percent Arcsine* check 10 .70 ».» a diazinon (0,75 lbs./lOO lbs.) 27 .60 31.75 ab Bayer 39007 " 47 .10 43.30 abc Bidrin (0.50 lbs./ 100 lbs.) 55 80 48.32 abc endrin " 62 00 51.95 bed Bayer 25141 82 30 65.15 cd G.C. 6506 (0.25 lbs./lOO lbs.) 96 80 79.70 d *Any two means followed by the same letter are not significantly different at the 1% level. Significance based on Duncan's test.

PAGE 64

58 and G.C. 6506 were highly significantly better than the check, whereas diazinon, Bayer 39007, and Bidrin were not significantly different from the check at the 1 percent level.

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SUMMARY AND CONCLUSIONS Control of the lesser cornstalk borer has been reported as impossible once the larvae are within the plants. The sporadic and spotty manner in which infestations by this pest occur does not afford satisfactory samples for field plot experiments in control. In this work, the lesser cornstalk borer was mass-reared in the laboratory. The larvae were grown in a wheat germ base diet devised for rearing larvae of Heliothis species (Berger 1963). For mating and oviposition, the adults were placed in screen cages at a concentration of at least ten moths per cubic foot, with equal proportions of males and females. The cages were kept in a bioclimatic chamber at about 27°C and 60 percent relative humidity, and with 14 hour periods of light. Measurements and observations of the different stages of the insect were made and found to coincide with those made by Luginbill and Ainslie (1917) and Sanchez (1960). Greenhouse experiments in chemical control were conducted on artificially infested seedlings of Dixie 18 corn. A layer of dry soil was placed around the seedlings and infestation carried out by sinking paper strips with eggs in the soil in contact with the stem, or by placing third or fourth instar larvae on dry loose soil at the base of the seedlings. Highly significant control was obtained with treatments of Bayer 25141, G.C. 6506, diazinon, endrin, dimethoate, azinphosmethyl, heptachlor, disulfoton, and Bidrin in emulsion form; trichlorfon and Bayer 39007 59

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60 wettable powders, and phorate granules. The insecticides were applied to the base of the plants at the rate of 1 lb. of active material per acre soon after the first signs of infestation appeared. G.C. 6506, endrin, Bayer 25141, and diazinon applied to the base of the seedlings in emulsion form at the rate of 1 lb. of active material per acre gave a high level of protection against subsequent infestation with fourth ins tar larvae. Infested seedlings in light and heavy soil were treated with endrin, diazinon, Bayer 25141, and dimethoate at the rate of 1 lb. per acre in emulsion form, and 2 lbs. per acre in granular form. Endrin and diazinon gave the best control on both types of soil, whereas Bayer 25141 gave about the same level of control in heavy soil as did endrin and diazinon, but a much lower one in light soil. Dimethoate was poor in both soils. The four chemicals gave better control in liquid applications, despite the fact that twice as much technical material was used in the granular applications . When Dixie 18 corn seed was treated with Bidrin, Bayer 25141, diazinon, endrin, heptachlor, Bayer 39007, and azinphosmethyl at the rate of 1 lb./lOO lbs. of seed, and with G.C. 6506 at 0.25 lbs./lOO lbs. of seed, the seedlings were given a highly significant level of protection. In one experiment to test the residual effect of several insecticides applied as seed treatments, endrin, Bayer 25141, and G.C. 6506 were highly significantly better than the check. In this test, however, endrin and Bayer 25141 caused phytotoxicity at rates higher than 0.5 lbs./lOO lbs. of seed.

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61 Signs of infestation began to show about ten days after the plants were infested, and for the following thr ee or four days, appeared in from 5 to 10 percent of the infested plants. A high percent of control was obtained with some insecticides if the treatment was made during those three or four days, in which case even the plants showing signs of infestation recovered. Mortality of the seedlings was almost 100 percent in the untreated plots. Chemical insecticides are effective in the control of lesser cornstalk borer attacking corn seedlings, especially when the chemicals are applied in water to the base of the plants, if the treatments are made soon after the appearance of signs of infestation.

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LITERATURE CITED Anonymous. 1937. Report of the Puerto Rico Experiment Station. 115 pp. Washington, D. C. 1939 Rev. Appl. Entomol. Ser. A. 27:501. Arthur, B. W. and F. S. Arant. 1956. Control of soil insects attacking peanuts. J. Econ. Entomol. 49(1):68-71. Berger, R. S. 1963. Laboratory techniques for rearing Heliothis species on artificial medium. USDA, ARS-33-84. Billings, S. C. 1963. Consolidated list of new approved common names of insecticides and other pesticides. Bull. Entomol. Soc. Am. 9(3): 189-197. . 1965. Consolidated list of approved common names of insecticides and certain other pesticides. Bull. Entomol. Soc. Am. 11 (3): 204-213. ^Bissell, T. L. and M. Dupree. 1947. Vegetable insect pests. Georgia Agric. Exp. Stat. Bull. 254:7-8. Box, H. E. 1929. Sobre las plagas insectiles de la cana de azucar. Rev. Ind. Agric. Tucuman 19(7-8): 212. Cowan, P. F. and A. H. Dempsey. 1949. Pimiento production in Georgia. Georgia Agric. Exp. Sta. Bull. 259:17. Cunningham, W. H., Jr., D. R. King, and B. C. Langley. 1959. Insecticidal control of the lesser cornstalk borer. J. Econ. Entomol. 52(2): 329-330. Dugas, A. L., C. E. Smith, and E. J. Concienne. 1948. Parathion found effective against the fall armyworm and the lesser cornstalk borer. In Louisiana Agric. Exp. Sta. Annu. Rept. p. 70-71. J Dupree, M. 1964. Insecticidal and cultural control of the lesser cornstalk borer. Georgia Experiment Sta. Mimeo. Ser. 197. Falanghe, 0. 1958. 0 combate as pragas do trigo proporciona melhores colheitas. Biologico 24(3):42-45. Harding, J. A. 1960. Control of the lesser cornstalk borer attacking peanuts. J. Econ. Entomol. 53 (4) :664-667 . Hayward, K. J. 1943. La polilla taladradora de la cana de azucar (Elas mopalpus lignosellus (Zeller). Bol. Est. Exp. Agric. Tucuman 49:9. J Heinrich, C. 1956. American moths of the subfamily Phycitinae. U. S. Nat. Mus. Bull. 207. 62

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63 Hills, W. A., J. F. Darby, W. H. Thames, and W. T. Forsee. 1953. Bush snap bean production on sandy soils of Florida. Florida Agric. Exp. Sta. Bull. 530:22. Hyche, L. and W. G. Eden. 1954. Control of the lesser cornstalk borer on beans and peas. In Alabama Agric. Exp. Sta. Annu. Rept. 64-65: 50. Ingram, J. W., H. A. Jaynes, and R. N. Lobdell. 1939. Sugar cane pests in Florida. In Proc. Int. Soc. Sug. Cane Tech. 6:89-98. J Isley, D. and F. D. Miner. 1944. The lesser cornstalk borer, a pest of fall beans. J. Kansas Entomol. Soc. 17 (2): 51-57. Kelsheimer, E. G., N. C. Hayslip, and J. W. Wilson. 1950. Control of bud worms, earworms, and other insects attacking sweetcorn and green corn in Florida. Florida Agric. Exp. Sta. Bull. 466:31-36. Kulash, W. M. 1948. Benzene hexachloride-DDT combination for pest control. J. Econ. Entomol. 41 (6):912-913. Lauderdale, J. L. E. 1920. Annual report of the assistant entomologist at Yuma. 11th. Annu. Rept. Arizona Commis. Agric. & Hort. 19181919. 1921. Rev. Appl. Entomol. Ser. A (9):408. J Leuck, D. B. ? and M. Dupree. 1965. Parasites of the lesser cornstalk borer. J. Econ. Entomol. 58 (4): 779. Luginbill, P. and G. G. Ainslie. 1917. The lesser cornstalk borer. USDA Ent. Bull. 539. j Lyle, C. 1927. The lesser cornstalk borer (Elasmopalpus lignosellus (Zeller)). Mississippi State Plant Bd. Quart. Bull. 7 (2):2-3. Neave, S. A. 1940. Nomenclator Zoologicus. Vol. III. Zoological Society of London. 1065 pp. Plank, H. K. 1928. The lesser cornstalk borer (Elasmopalpus lignosellus (Zeller)) injuring sugar cane in Cuba. J. Econ. Entomol. 21 (2): 413-417. Reynolds, H. T., T. R. Fukuto, R. L. Metcalf, and R. B. March. 1957. Seed treatments of field crops with systemic insecticides. J. Econ. Entomol. 50 (5): 527-539. Reynolds, H. T., L. D. Anderson, and L. A. Andres. 1959. Cultural and chemical control of the lesser cornstalk borer in southern California. J. Econ. Entomol. 52 (1): 63-66.

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64 J Riley, C. V. 1882. The smaller cornstalk borer (Pempelia lignosella Zeller). In USDA Rept. 1881. pp. 142-145. Sanchez, L. 0. 1960. The biology and control of the lesser cornstalk -borer, Elasmopalpus lignosellus (Zeller). Unpublished Doctoral dissertation, Texas Agricultural and Mechanical College. Sauer, H. F. G. 1939. Kotas sobre Elasmopalpus lignosellus (Zeller) (Lepidoptera, Pyralidae) seria praga dos cereais no estado de Sao Paulo. Arq. Inst. Biol. pp. 199-206. Stahl, C. F. 1930. The lesser cornstalk borer (Elasmopalpus lignosellus , (Zeller)) attacking strawberry plants. J. Econ. Entomol. 23 (2): 466, -' Stuckey, H. P. 1945. The lesser cornstalk borer. Georgia Exp. Sta. ^ 57th Annu. Rept. pp. 63-64. Vorhies, C. T. and L. P. Wehr.le. 1946. Pest problems of the small garden. Arizona Agric. Exp. Sta. Bull. 203:32-33. S J Watson, J. R. 1917. The lesser cornstalk borer ( Elasmopalpus lignosellus (Zeller)). Florida Agric. Exp. Sta. Bull. 134:54. Willie, J. E. 1942. Insectos cue atacan a las leguminosas cultivadas. Vida Agric o la 19 (222) :347-349 . Wilson, J. W. , and E. G. Kelsheimer. 1955. Production of southern peas in Florida. Insects and their control. Florida Agric. Exp. Sta. Bull. 557:18.

PAGE 71

APPENDIX

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TABLE 10 PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 1 REPLICATIONS Treatments T JTT i. L TT T III 1. andosulfan 7/16 n/7 u/ / 0/ 11 2. disulfotan 7/18 Q/i n o /in 3. G.C. 6506 14/17 1 6/1 fi 1/./17 4. check 0/14 n/Q ft 1*1 'S U/ 1Z 5. endrin 16/17 1 9/1 A i.J/ lj 6. azinphosmethyl 15/17 A—/ / JL § 8/1 Q O/ i.7 y/ 1Z 7. diazinon 10/11 i n/i n 11/ 14 8. Bidrin 0/8 5/10 5/9 9. trichlorfon 5/13 9/9 7/12 10. dimethoate 11/13 10/11 10/12 11. Bayer 25141 10/10 10/10 12/14 12. ethion 0/8 7/11 6/10 13. Kepone 0/11 2/15 2/14 14. heptachlor 17/19 6/10 9/15 15. phorate 11/17 12/14 10/15 16. Bayer 39007 6/17 5/15 7/18

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67 TABLE 11 PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 2 REPLICATIONS Treatments I II ill iy 1. endrin 9/11 10/10 13/14 10/10 2. check 4/10 0/10 0/13 0/14 3. Bayer 25141 10/11 9/9 9/11 16/16 4. diazinon 11/11 12/13 7/8 11/13 5. G.C. 6506 12/12 11/11 14/14 14/15

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68 TABLE 12 PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 3 REPLICATIONS Treatments I TT ttt w § endrin 10/14 4/14 ' 10/14 diazinon 13/16 4/14 14/16 T— , r\ r~ ~\ / "\ -% j*x / -t s~ aims # — Bayer 25141 10/16 4/14 2/16 dimethoate 2/16 2/16 0/14 check 0/16 0/15 0/16 EMULSION endrin 15/16 12/14 8/10 diazinon 11/14 7/10 14/16 oayer Z5141 //lo 4/12 8/16 dimethoate 5/16 2/16 7/16 check 0/14 0/10 0/16 CIAY c endrin 8/14 10/19 11/14 diazinon 5/16 8/15 16/18 Bayer 25141 10/14 14/17 8/17 dimethoate 1/19 1/19 2/15 check 0/15 0/16 0/18 I H t/ 0 ) i 1 endrin 10/15 10/13 13/16 diazinon 12/16 15/17 12/22 Bayer 25141 14/17 11/18 13/17 dimethoate 8/15 8/18 1/17 check 0/16 0/19 0/15

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TABLE 13 PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 4 REPLICATIONS i r ea tTnent s I II III x» azinpnosnie cny i 4/ ID 12/15 8/12 / CiTiHrtciil fan J/ 1U 0/11 4/10 •J* D1UI 111 \J • J IDS, 0/ 11 8/11 8/11 t . ecniou 2/10 0/10 4/18 j» ncpLacnxor o/ 10 10/10 7/10 ft /I "J TT1Q f~ Vl /~\ O I /•* o/ 11 1/10 3/10 7 Rauor ^QHH7 / • Ddyer J7UU/ y/y 6/11 8/11 2/ 11 2/11 2/12 9. G.C. 6506 0.25 lbs. 7/10 11/11 8/10 10. endrin 10/10 7/10 9/12 11. diazinon 8/9 8/9 9/10 12. Bayer 25141 9/10 8/9 8/9 13. Bidrin 1.0 lb. 9/9 10/11 9/10 14. trichlorfon 1/11 4/8 4/10 15. check 1/11 0/9 0/10 16. disulfoton 3/9 0/10 2/10 17. G.C. 6506 0.5 lbs. 5/10 12/14 8/9

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TABLE 14 PROPORTIONS OF SURVIVING CORN PLANTS FROM INDIVIDUAL PLOTS OF EXPERIMENT NO. 5 Treatments • I 1. diazinon 8/14 2. Bayer 25141 10/12 3. check 2/20 4. G.C. 6506 12/14 5. Bidrin 6/12 6. Bayer 39007 12/20 7. endrin 10/20 REPLICATIONS II III IV 6/18 2/18 2/12 18/18 10/12 4/10 4/20 0/20 6/22 18/20 6/6 2/2 12/16 10/18 6/14 6/20 4/20 10/20 6/18 18/20 14/20

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BIOGRAPHICAL SKETCH Jose R. Calvo was born February 24, 1929, at Cartago, Costa Rica. He obtained his elementary and secondary education at Cartago, Costa Rica, and was graduated from Colegio San Luis Gonzaga in February 1949. In February 1953 he received the degree of Agronomist from the Escuela Agricola Panamericana in Honduras. He taught field crops at the Tropical School of Agriculture in Daule, Ecuador until April 1954. In June 1956 he received the degree of Bachelor of Science from the University of Florida and went to head the Department of Agronomy of the National School of Agriculture of El Salvador. In 1959 he enrolled in the Graduate School of the University of Florida and received the degree of Master of Agriculture in June 1960, when he resumed his position at the National School of Agriculture of El Salvador. In 1962 he was appointed assistant professor in the Department of Agronomy of the Escuela Agricola Panamericana in Honduras. From September 1963 until the present time he has pursued his work toward the degree of Doctor of Philosophy. Jose' R. Calvo is married to the former Rhina Samayoa and is the father of three children. He is a member of the Entomological Society of America, the Florida Entomological Society, Pi Sigma, Alpha Tau Alpha, and Alpha Zeta. 71

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This dissertation was prepared under the direction of the chairman of the candidate's supervisory committee and has been approved by all members of that committee. It was submitted to the Dean of the College of Agriculture and to the Graduate Council, and was approved as partial fulfillment of the requirements for the degree of Doctor of Philosophy. April 23, 1966 , Dean, College of Agriculture Dean, Graduate School SUPERVISORY COMMITTEE:


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