Cabbage looper, soybean looper, and tobacco budworm populations near Quincy, Florida

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Title:
Cabbage looper, soybean looper, and tobacco budworm populations near Quincy, Florida seasonal abundance, host preference, and suppression by natural enemies
Physical Description:
xix, 255 leaves : ill. ; 28 cm.
Language:
English
Creator:
Martin, Paul Bain, 1946-
Publication Date:

Subjects

Subjects / Keywords:
Cabbage looper   ( lcsh )
Soybean -- Diseases and pests   ( lcsh )
Helicoverpa armigera   ( lcsh )
Heliothis zea   ( lcsh )
Genre:
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Thesis:
Thesis--University of Florida.
Bibliography:
Includes bibliographical references (leaves 222-241).
Statement of Responsibility:
by Paul Bain Martin.
General Note:
Typescript.
General Note:
Vita.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 000408116
notis - ACF4529
oclc - 02172782
System ID:
AA00003515:00001

Full Text















CABBAGE LOOPER, SOYBEAN LOOPER, AND TOBACCO PEL','.-*!
POPULA'I7l :. NEAR QUINCY, FLORIDA: -F.1LONAL ABUNDANCE,
HOSTf PREFERENCE, AND L._T F?. .:',. BY NATURAL ENEMIES














By

PAUL, BAIN MARTIN


A DISE :RTATII, PRESENTED TO THE GPAD'ATE C7 JI'-'-: OF
THE ". .i'2ITY OF FLO~RDA
IN FAIITIAL FULFIL'.U'- C:" TH PEQUI'tL:'_iETS E 1' THE
DEGREE OF DOCT'Cri OF PhILCPIHY













UNIVERSITY OF FLO2RDA


1976














ACK!i.-J EDGN NTS


Many have assisted in the construction of this dissertation and I am

grateful to them. Dr. P.'D. Lingren brought me to Florida and this re-

search, and was always eager to help as an advisor, prodder, and friend.

Dr. R. I. Sailer, who served as committee chairman, was generous in yield-

ing time to assist with problems concerning my research, course work, writ-

ing and other matters. Dr. G. L. Greene was helpful with his constructive

criticism and guidance, and helped in obtaining work space, equipment,

and materials. Drs. W. H. Whitcomb and J. Reiskind helped very much with

their advice, guidance, criticism, and other assistance.

I am thankful for my wife, Betsy, who has been tolerant, patient,

and encouraging. In addition, she assisted as technician, collator,

typist, and proofreader.

Without the training received from my father and mother, I would

never have completed this work. And Mr. L. C. Martin, Dr. Joseph Schaffner,

and Dr. R. L. Ridgway were the most important individuals in initiating

my pursuit of knowledge in entomology.

The major supportt (financial and otherwise) came as a result of

a cooperative effort of the Southern Region, Agr. Res. Serv., CSDA,

Quincy, FL location, and the Agr. Res. and Educ. Center, IFAS, Quincy, FL

(Cocperative Agreement no. 12-14-100-10, 914(33)). Assistance was also pro-

vidYd by the Dep. of Entomol. and Nematol., Univ. of Florida, and by

Peggie Martin and Associates, Inc., Pearsall, TX, in the last few months

of work on this dissertation.








The development of the research presented herein depended greatly on

the taxonomic assistance (with collected specimens) by E. E. Grissell,

Div. Plant Industry, Gainesville, FL, P. M. Marsh, C. F. W. Muesebeck,

and R. W. Carlson, Systematic Entomol. Laboratory, Beltsville, MD

(Hymenoptera); C. Tauber, Cornell Univ., Ithaca, NY (Neuroptera); L. R.

Ertle, Agr. Res. Serv., USDA, Newark, DE, and S. Nagarkatti, CIBC,

Bangalore, India (egg parasitoids); F. W. Mead, Div. Plant Industry, and

R. I. Sailer, Univ. of Florida (Hemiptera); R. E. Waites, Univ. of

Florida, and R. D. Gordon, Systematic Entomol. Laboratory (coccinellids);

W. H. Whitcomb, Univ. of Florida cretaceouss arthropods); B. Puttler,

D. L. Hostetter, C. M. Ignoffo, and R. E. Pinnell, North Central Region,

Agr. Res. Serv., USDA, Columbia, MO, (parasitoids and pathogens); H. V.

Weems, Div. Plant Industry, and C. W. Sabrosky, Systematic Entomol.

Laboratory (tachinids); and R. E. Woodruff, Div. Plant Irndstr'y (Coleoptera).

Insects provided by A. H. Baumhover, Southern Region, Agr. Res. Serv.,

USLA, Oxford, NC, and R. K. Morrison and R. E. Kinzer, Southern Region,

Agr. Res. Serv., USDA, College Station, TX, and planting material

furnished by W. B. Tappan and R. L. Stanley, Agr. Res. and Educ. Center,

Quincy, FL, are appreciated. Work space provided by D. Davis and T.

Newsome, Southern Region, Agr. Res. Serve USDA, Gainesville, FL, is

gratefully acknowledged.

Especially helLful in providing information, assistance, and/or

suggestions were W. G. Eden, W. H. Chapman, V. Perry, D. Fish, R. Crocker,

G. D. Butler, Jr., J. O. Strandberg, and N. Lappla. Typists and technicians

who were most helpful with this research included P. Whiteiurst, A. Brown,

T. Bowers, J. T. Suber, W. R. van Landingham, G. Winqfield, B. Spires,

and J. Walden.








I am very grateful to L. C. Martin, O. Doyal, and H. Hernandez for

their- patience in the final months of my completion of this dissertation.


















TABLE OF C'.iTENIT




Page



ACK'l WLEDGCrE4j'3 ........................................... i

LIST OF TABLES ................... ............... ..... .... ix

LIST OF FIGURES ......... ........................... ...... xiii

ABSTRACT ...................................................... vii

SECTION

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

General Methods and Materials ....................... 2
Eight-Acre Cropping System ....................... 2
Whole plant inspections, sweeps, and
plant shakes ...................... ............. 6 -
Collections of immatures ..................... 7
D-vac samples .. ................................ 8
Wild Hosts .......... ... ......................... 8
One-Acre Shade ...................... ............ 9

II SEAS:'IAL ABUNDANCE AND HOST PREFERENCE .............. 13

Literature Review .......................... ........ .. 14
Seasonal Occurrence and Abundance ................ 14
Cabbage looper ................................. 14
Soybean looper .................................... 19
Tobacco budworm ......... ..................... 20
Host Preference ................... ............... 26
Cabbage 1:r .................................. 26
Soybean locic r ............... ................ 26
Tobacco budwozm .............................. 27
Methods and Matrials .............................. ...
Seasonal Occurrence and Abundance ................ 28
Host Preferences ................................. 29
Results ard Discussion ...... ........................ 31










Page


Seasonal Occurrence and Abundance ............... 31
Cabbage looper .............................. 31
Soybean looper .................................. 38
Tobacco budworm ............................. 44
Host Preference ................................... 54
Cabbage looper ............................... 54
Soybean looper .............................. 56
Tobacco budworm ............... .... ........ 57
Summary ........ ... ........... .......... ............. 59

III PAPASITOIDS AND PATHOGENS .......................... 61

Literature Review ............... ................... 63
Cabbage Looper ................................. 63
Parasitoids ................ .. ............... 63
Pathogens .................................... 67
Soybean Looper ................................... 68
Parasitoids ................................ 68
Pathogens ................. ................... 69
Tobacco Budworm ................................. 70
Parasitoids ................................... 70
Pathogens ................................... 74
Methods and Materials .............................. 74
Results and Discussion ........................... 77
Parasitoids ....................................... 77
Seasonal occurrence .......................... 80
Host stages utilized ......................... 83
Parasitization of cabbage looper ............. 88
Eggs ...................................... 88
Larvae ................ ...................... 90
Parasitization of soybean looper ............. 92
Eggs ................. ...................... 92
Larvae ...................................... 94
Parasitization of tobacco buddornr ............ 94
Eggs ........................ ... ..... ..... 94
Larvae ............ ......................... 97
Alternate hosts .............................. 99
Cabbage looper parasitoids ............... 100
Soybean lo'.perr aisitoi-1s ............... 102
Tobacco budworm caresitoid3 ............... 102
Host habitat ................................... 104
Pathogens ..................... ........ ........ ... 108
Cabbage looper .............................. 108
Soybean looper ................................ 108
Tobacco budworm ........................... .. 110
Alternate hosts ................................ 110
Sutmary .............................................. 113









Page


IV PREDACEOUS ARTHROPODS ................................. 116

Literature Review ..................................... 117
Predators of Cabbage Locper ......................... 122
Predators of Soybean Looper ....................... 127
Predators of Tobacco Budworm ....................... 128
Methods and Materials ................................. 133
Results and Discussion ................................ 135
The Predator Complex .............................. 138
Sources ...... ............................... 140
Predators Associated with Ca-bhage Looper ........... 148
Predators Associated with Soybean Looper ........... 157
Predators Associated with Tobacco Budworm ........... 166
Summary ................................................. 184

V RELEASES OF SUPPLEMENTAL Trichogramma pretiosum
AND Chrysopa carnea ................................. 186

Literature Review ..................................... 187
Trichogramma pretiosum .............................. 187
Chrysopa carnea .................. .................. 189
Methods and Materials ................................ 190
Trichogramma pretiosum ............................ 190
Chrysopa carnea .... ............................... 194
Results and Discussion ............................... 197
Trichogramma pretiosum ........................ .. 197
Cabbage looper ................................. 197
Soybean looper ................................. 202
Tobacco budworm ................................ 203
Effect of hosts and host-habitats .............. 204
Chrysopa carnea ................................... 207
Summary ................................................. 216

VI CONCLUSIONS ........................................... 218

Cabbage Looper ......................................... 218
Soybean Looper ....................... ................. 219
Tobacco Budworm ....................................... 220

REFERENCES ......................................... .. ..... 222

APPENDICES

A Predaceous Hemiptera in an 8-acre crowning
system ................................................ 243

B Seasonal abundance and species composition of
Chrysopa in crops in an 8-acre cropping system,
from December, 1971-August, 1973 .................... 244


vii









Page

C Seasonal abundance and species composition of
Micromus in crops in an 8-acre cropping system
from December, 1971-August, 1973 .................... ... 245

D Relative abundance of ants in crops in an 8-
acre cropping system ................. ............... 246

E Seasonal abundance of Geocoris spp. in crops
in an 8-acre cropping system ....................... 247

F Relative and seasonal abundance of selected
predaceous arthropods in rye ........................ 250

G Relative and seasonal abundance of selected predaceous
arthropods in wheat .....;.... ..................... 251

H Relative and seasonal abundance of selected
predaceous arthropods in sweet corn,
field corn, sorghum, and millet ................... 252

BIOGRAPHICAL SKETCH .......................................... 254


viii

















LIST OF TABLES


Table Page

1 Schedule of cultural practices and of releases
of cabbage looper, soybean looper, and tobacco
budworm in a 1-acre tobacco shade, Quincy, FL,
July-September, 1971. 10

2 Relative occurrence of species of Plusiinae
collected in crops in an 8-acre cropping system. 32

3 Relative number of immatures of cabbage looper
in collards and cabbage in an 8-acre cropping
system during the spring of 1972 and 1973. 34

4 Degree of mating of cabbage looper, soybean looper,
and tobacco budworm females trrapr.'e in cabbage
looper pheromone-baited light traps surrounding
an 8-acre cropping system. 40

5 Relative number of larvae of soybean looper in
soybeans, tomatoes, and peanuts in an 8-acre crop-
ping system during the summer of 1972. 42

6 Relative occurrence of species of Heliothis col-
lected in crops in an 8-acre cropping system. 45

7 Relative number of immatures of tobacco budvorm
in flue-cured and cigar-wrapper tobacco in an
8-acre cropping system in 1973. 49

8 Parasitoids of cabbage looper found in field
studies in the United States. 64

9 Major parasitoids of the tobacco budworm found
in the United States. 71

10 Parasitoids reared from immature cabbage loopers,
soybean loopers, tobacco budworms, and other
Lepidoptera collected from an 8-acre cropping
system and in nearby wild hosts. 78










Table Page

11 Relative occurrence of parasitoids of larvae of
Plusiinae, primarily cabbage looper, in various
crops in an 8-acre cropping system. 91

12 Relative occurrence of parasitoids of larvae of
Plusiinae, primarily soybean looper, in various
crops in an 8-acre cropping system. 95

13 Relative occurrence of parasitoias of larvae of
Heliothis spp., primarily tobacco budworm, in
various crops in an 8-acre cropping system and
in nearby wild hosts. 98

14 Relative occurrence of parasitoids of larvae of
Plusiinae other than cabbage and soybean looper
in various crops in an S-acre cropping system and
in nearby wild hosts. 103

15 Relative occurrence of parasitoids of larvae of
Heliothis spp., primarily corn earworm, in various
crops in an 8-acre cropping system and in nearby
wild hosts. 105

16 Incidence of diseased larvae of Plusiinae in crops
in an 8-acre cropping system. 109

17 Incidence of diseased larvae of Heliothis spp.,
primarily tobacco budworm, in crops in an 8-acre
cropping system. 111

18 Incidence of diseased larvae of Heliothis spp.,
primarily corn earworm, in crops in an 8-acre
cropping system. 112

19 Arthropod predators observed feeding on cabhage
looper in the field. 125

20 Arthropod predators observed feeding on immatures
of the cabbage looper in the laboratory. 126

21 Arthropod predators observed feeding on soybean
looper in the laboratory or field. 129

22 Comparison of total number of selected predaceous
arthropods estimated from whole plant inspections
and D-vac samples in 5 crops of the 8-acre crop-
ping system from June 4-July 16, 1972. 136










Table Page

23 Comparison of number of individuals in 5
predaceous arthropod groups estimated from
whole plant inspections and D-vac samples
in white clover from July 9 to August 27, 1972. 137

24 Relative abundance of selected predaceous arthro-
pods found in 8-acre cropping system. 139

25 Relative abundance of selected predaceous arthro-
pods found in individual crops in an 8-acre crop-
ping system. 141

26 Relative and seasonal abundance of selected pre-
daceous arthropods in cabbage. 149

27 Relative and seasonal abundance of selected
predaceous arthropods in collards. 150

28 Relative and seasonal abundance of selected
predaceous arthropods in soybeans. 161

29 Relative and seasonal abundance of selected
predaceous arthropods in tomatoes. 165

30 Relative and seasonal abundance of selected
predaceous arthropods in white clover. 167

31 Relative and seasonal abundance of selected
predaceous arthropods in flue-cured tobacco. 174

32 Relative and seasonal abundance of selected
predaceous arthropods in cigar-.ilacper tobacco. 180

33 Relative and seasonal abundance of selected pre-
daceous arthropods in okra. 183

34 Comparison of parasitization and hatch of eggs of
Plusiinae and Heliothis spp. (1) collected prior
to Trichogramma pretiosum releases, (2) collected
irm mdiat-ly after the initial release of T.
pretiosum until 2 days after the last release,
and (3) collected 4 days after the final release
until sampling was terminated. 200

35 Parasitization rates of eggs of 3 non-target lepi-
dopterous species in crops grown in a 1-acre tobacco
shade (TS) and in a 1.3-acre soybean field (SBF)
after releases of Tri:hcIr rana.. pretiosum. 206










Table Page

36 Relative numbers of larvae of Chrysopa spp.
per 100 row-ft in release and control plots
found in crops in a 1-acre tobacco shade after
supplemental releases of 2- to 7-day-old C.
carnea larvae. 208

37 Rating of foliage da:-ce and percent fruit damage
for crops in a 1-acre tobacco shade after releases
of 2- to 7-day-old Chrysopa carnea. 212

38 Weather conditions for August and September, 1971
at the North Florida Agricultural Research and
Education Center, Quincy, FL. 214


xii

















LIST OF FIGURES


Figure Paq e

1 Crop rotation within an 8-acre cropping system
near Quincy, FL. 3

2 Crop layout in a 1-acre tobacco shade, Quincy,
FL, July-September, 1971. 11

3 Mean number of cabbage looper, soybean looper, and
tobacco budworm adults (mostly males) caught per
blacklight trap baited with synthetic cabbage
looper pheromone, or electric grid trap baited
with virgin female cabbage looper or tobacco bud-
worm/night compared with mean number of eggs of
Plusiinae or Heliothis spp. in preferred crops
in an 8-acre cropping system. 35

4 Seasonal abundance of eggs and larvae of cabbage
looper in collards, and soybean looper in soy-
beans, in an 8-acre cropping system. 36

5 Rates of increase of cabbage looper, soybean
looper, and tobacco budworm indicated by cabbage
looper pheromone-baited blacklight trap captures
of adults. 39

6 Seasonal abundance of eggs and larvae of tobacco
budworm in flue-cured tobacco, okra, and white
clover in an 8-acre cropping system. 47

7 Mean number of eggs or larvae of cabbage looper,
soybean looper, and tobacco budworm per sample
date in 7 crops compared in a 1-acre shade, a
6- x 4- x 5-ft cage, and an 8-acre cropping sys-
tem. Cockleburs were included in the small cage. 55

8 Seasonal occurrence of parasitoids of the cab-
bage looper, soybean looper, and tobacco bud-
worm in an 8-acre cropping system and a 1-acre
shade during 1971, 1972, and 1973. 81


xiii









Figure Page

9 Parasitoids of the cabbage looper reared
from larvae collected when small (S), medium
(M), and large (L). 85

10 Parasitoids of the soybean looper reared from
larvae collected when small (S), medium (M),
and large (L). 86

11 Parasitoids of the tobacco budworm reared from
larvae collected when small (S), medium (M), and
large (L). 87

12 Seasonal parasitization of Plusiinae eggs and
larvae, primarily cabbage looper, in collards,
cabbage, and tomatoes in an 8-acre cropping
system. 89

13 Seasonal parasitization of Plusiinae eggs and
larvae, primarily soybean looper, in soybeans
and tomatoes in an 8-acre cropping system. 93

14 Seasonal parasitization of eggs and larvae of
Heliothis spp. in flue-cured tobacco, cigar-
wrapper tobacco, okra, tomatoes and white
clover in an 8-acre cropping system. 96

15 Seasonal parasitization of eggs and larvae of
Plusiinae other than cabbage and soybean looper
in white clover and field peas in an 8-acre crop-
ping system. 101

16 Seasonal parasitization of eggs and larvae of
corn earworm in field corn, sweet corn, sorghum,
and squash in an 8-acre cropping system. 106

17 Relative number of eggs plus small larvae of
cabbage looper, medium plus large larvae of
cabbage looper, total selected predaceous
arthropods, and large predaceous coccinellids
154
in cabbage.

18 Relative number of eggs plus small larvae of
cabbage looper, medium plus large larvae of
cabbage looper, total selected predaceous arthro-
pods, and large predaceous coccinellids in
collards. 156


xiv










Figure Page

19 Relative number of eggs plus small larvae of
soybean looper, medium plus large larvae of
soybean looper, total selected predaceous
arthropods, and selected predaceous Hemiptera
in soybeans. 160

20 Relative number of eggs plus small larvae of
Plusiinae, medium plus large larvae of Plusiinae
total selected predaceous arthropods, and
selected predaceous Hemiptera in tomatoes. 164

21 Relative number of small larvae of Heliothis
spp. medium plus large larvae of Heliothis spp.,
total selected predaceous arthropods, large
predaceous coccinellids, and selected predaceous
Hemiitera in white clover. 170

22 Relative number of eggs plus small larvae of
Heliothis spp., medium plus large larvae of
Heliothis spp., total selected predaceous
arthropods, and selected predaceous iemiptera
in tomatoes. 172

23 Relative number of eggs plus small larvae of
tobacco budworm, medium plus large larvae of
tobacco budworm, total selected predaceous
arthropods, and selected predaceous Hemiptera
in flue-cured tobacco. 176

24 Relative number of eggs plus small larvae of
tobacco budworm, total selected predaceous
arthropods, large predaceous coccinellids, and
selected predaceous Hemiptera in cigar-wrapper
tobacco. 178

25 Relative number of eggs plus small larvae of
tobacco budworm, total selected predaceous
arthropods, large predaceous coccinellids, and
selected predaceous Hemiptera in okra. 182

26 Parasitization of eggs of Plusiinae and relative
densities of eggs and larvae of Plusiinae,
primarily cabbage looper, on 5 crops in a 1-acre
tobacco shade after 3 releases of ca. 230,000
female Trichogramma pretiosum per acre/release. 198









Figure Page

27 Parasitization of eggs of Heliothis spp.
and relative densities of eggs and larvae
of Heliothis spp. on 3 crops in a 1-acre
tobacco shade after 3 releases of ca.
230,000 female Trichogramma pretiosum
per acre/release. 199

28 Relative number of eggs and larvae of
Plusiinae per acre in release and in con-
trol plots in 5 crops in a 1-acre tobacco
shade after 3 releases of ca. 194,000
two- to 5-day-old Chrysopa carnea larvae/
acre/release. 209

29 Relative number of eggs and larvae of
Heliothis spp. per acre in release and in
control plots in 3 crops in a 1-acre tobacco
shade after 3 releases of ca. 194,000 two-
to 5-day-old Chrysopa carnea larvae/acre/
release. 211


xvi










Abstract of Dissertation Presented to the Graduate Coauncil
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philc*-ophy


CABBAGE LCDPEP, SOYBEAN LOFEF., AND TOBACCO BUEDWC',IPJr P.FFUL-TIC!NS
NEAR QUINCY, FLORIDA:
SEASONAL ;I. .NC!'.E, HOST PREFERENCE,
AND SUPPRESSION BY NATURAL EC.AEMILS

By

Faul Bain Martin

March, 1976


Chairman: Dr. R. I. Sailer
Co-Chairman: Dr. G. L. Greene
Major Department: Entomology and Nematology


Population dynamics of the cabbage looper, Trich.oplusia ni

(Hibner), the soybean looper, PsL.dcrlusia includes (Walker), and

the tobacco budworm, Heliothis virescens (F.), were investigated in

an 8-acre cropring system, including tobacco, soybeans, and 18 other

crops, and in some additional study areas. Discovery cf critical

factors influencing interaction between host and natural enemy popu-

lations was the primary research objective. Results should aid in

developing management practices designed to minimize economic losses

caused by these pests.

Cabbage looper was found during most months in its most utilized

host, collards, and reached highest densities in May, June, and Sep-

tember. Collards and cabbage were preferred hosts. Also, catches in

pheromone-baited blacklight and grid traps were positively correlated

to number of immatures in the field during 1 year.

Soybean looper was found on its preferred host, soybeans, and a

few other hosts, at much lower densities than cabbage looper. It


xvii








occurred in the system from June to October. Blacklight trap catches

were indicative of immatures of soy-bean looper in the field.

Tobacco budworms occurred in the system from early or mid-April

through October in several wild hosts, in white clover, tomatoes,

tobacco, and okra. Tobacco was the preferred host. Densities of this

pest within the system were similar to those of the cabbage looper.

Prediction of these densities of tobacco budworm immatures by utilizing

data from adult traps appeared promising.

Copidosoma truncatellum (Dalman), Meteorus autographae Muesebeck,

and Voria ruralis Fallen were the most important larval parasitoids

recovered from cabbage loopers; Trichogramma spp. was by far the major

egg parasitoid. Parasitization of eggs and larvae in crucifers ranged

from 0 to 55% and 0 to 100%, respectively, and was generally highest

during the spring and fall. Parasitization of cabbage looper iummatures

was generally highest in tomatoes. Larval populations of cabbage looper

were decimated by nuclear polyhedrosis virus after reaching high densi-

ties in the summer.

The parasitoid complex for the soybean looper was similar to that

for the cabbage looper. Parasitization of soybean looper larvae was

generally high but eggs in soybeans were seldom attacked. Larvae were

seldom diseased; however, the most frequent pathogen was Nomuraea sp.

Tobacco budworm eggs were rarely parasitized in tobacco, but were

frequently parasitized in tomatoes and okra. Parasitization of tobacco

budworm larvae in tobacco was usually over 50% and was mostly by

Cardiochiles nigriceps Viereck. Incidence of disease, even during

high densities of tobacco budworm larvae, was low to moderate.


xviii










The primary predaceous arthropods associated with the cabbage

looper and tobacco budworm were Cclecrecilla maculata (DeGeer) and

Hippodamia convergens (Gucrin-Meneville). Geocoris punctipes (Say)

was the most prevalent predator in soybeans, although several other

predaceous arthropods were also numerous in this host of the soybean

looper. White clover was the most important reservoir of predaceous

arthropods, although corn, sorghum, millet, and some other crops

were also quite important as sources of predators.

Cabbage loopers in crucifers and tobacco budworms in tobacco

were probably not substantially sujpressed by predaceous arthropods.

However, soybean loopers in soybeans and tobacco budworms in white

clover and okra were apparently suppressed to low to moderate densi-

ties by these entomophages.

Three supplemental releases of ca. 230,000 female Trichograrrma

pretiosum Riley per acre at 3-day intervals were an effective sup-

pressant of the 3 noctuids on tomatoes, soybeans, collards, and other

crops, but not on tobacco. Under conditions of the experiment, 3

releases of ca. 194,000 larvae of Chrysopa carnea Stephens per acre/

release at weekly intervals were not effective against the 3 ncctuids

in any crops tested.


xix
















SECTION I


INTRODUCTION


An understanding of the intra- and inter-specific relationships in

artificial supraorganismal systems and surrounding "natural" communities

is critical to effective applied control of organisms within these systems

(Allee et al. 1949). This is essentially the community concept as out-

lined by Odum (1959) -- if man deems it necessary to suppress a partic-

ular organism he will cause less disruption and suffer fewer detrimental

consequences if he intelligently modifies the community instead of making

a direct attack on the organism without regard to community consequences.

The research reported herein was an investigation of the relation-

ships of three noctuids, the cabbage looper, Trichoplusia ni (Hubner),

the soybean looper, Pseudoplusia includes (Walker), and the tobacco bud-

worm, Heliothis virescens (F.), and their natural enemies, in a relative-

ly simple system of crops, and in the absence of applied control. Addi-

tional knowledge of relationships of these insect pests, and the entomopha-

gous organisms and crops associated with them, should help provide insight

into means for more effectively regulating and suppressing these 3 often

economically injurious pests.

A primary objective was to find vulnerable areas in the 3 pests'

population cycles that might be exploited in suppressive manipulations

designed to maintain these pests at tolerable levels in tobacco, soybeans,

and other :rz-e1. Hopefully such knowledge will aid crop (or systems)









managers in developing more suitable means of control utilizing methods

compatible with the community concept.


General Methods and Materials


Eicht-.cre Cr:.rin. Sy-stem

A sequence of crops involving ca. 0.1-1.0 acre of collards, 0.6-0.9

acre of white clover (relatively "permanent" crops), 1.7 acre of cigar-

wrapper tobacco, 1.0 acre of flue-cured tobacco, 0.9-1.1 acre of soy-

beans, ca. 0.1 acre of cabbage, 0.1-0.5 acre of okra, 0.1-1.1 acre of

tomatoes, 0.9-1.0 acre of field corn, ca. 0.1 acre of sweet corn, ca.

0.1-0.3 of sorghum, 0.6-0.9 acre of millet, ca. 0.1-0.5 acre of southern

field peas, ca. 0.1 acre of bell peppers, ca. 0.1-0.6 acre of peanuts,

1.1 acre bush beans, 0.3 acre of squash, 0.5 acre of turnips, 0.3 acre

of pumpkins, 2.2-3.3 acre of rye, and 1.4-3.2 acre of wheat, were grown

on ca. 8 acres in an old tobacco shade (Kincaid 1960) that had not been

used for several years. 'The 8-acre cropping system was located ca. 6 mi

south of Quincy, Florida (Fig. 1).

The cigar-wrapper tobacco in the system was covered with loosely
2
woven cloth ("cheese cloth") of 8 x 10 threads per in. The sorghums

were grain sorghums in 1972 and a forage sorghum in 1973. Bahia grass

was on ca. 7 acres immediately surrounding the northeast, southeast, and

southwest sides of the system. Wild hosts occurring along a road were

present on the northwest side of the system (Fig. 1).

Of all the crops in the system, collards, flue-cured tobacco, field

corn, sweet corn, sorghum, bush beans, squash, turnips, pumpkins, field

peas, rye, and wheat were generally in the best growing condition. How-

ever, many collard plants did become diseased in July and August of 1972.















WINTER '71-72
23




23 23

22

SPRING '72
23



21



SUMMER '72
23






22 I
15i~ lC1 8

n jj


. \
v


FALL '72
23
15 11 ,



Svclunteer"
22 ci g.Nr-wrapper
i. tobacco

WINTER '72-73





23 23

22

SPRING-SUMMER '73



7 4 6 15

[ 1 los I I 12I 13
23 n23


NO. CROP (VARIETY) NG. ROWS
/16 FT PERIOD IN SYSTEM


RYE (WESER) DRILLED
WHEAT (WAKELAND) DsILLED
WHITE CLOVER (LA S-1, REGAL) BROAD-
CASTED
COLLARiS (VATES) 445
CABBAGE (EARLY ROUND DUTCH) 4
FLUF-CURED TOBACCO(COKER 298)
TOMATOES (HOMESTEAD) 4
SWEET CORN SILVERO QUEEN. 5
GOLDOCRST, ICANA)
SORGHUM (DEKALB BR-64, SAVANNAH-- Sr
1',72; FrUKS 102F--1973) BRAD
CASHED
CIGAR-WRAFPER TOBACCO (FL-17) 4
BELL PEPPER (lkRLD BEATER,KEYSTOnE 4
RESISTANT GIANT-3)
OKRA (LONG POD GREEN) 4
PEANUTS (TIF5PAN SPANISH RUNNER) 4
FIELD CORN(COKER 71.FIONEER 369A) 4
SOYBEANS (BRAGG) 4
FILLET (sTAR PEARL' BROAD-
CASTED
SOUTHERN FIELD PEAS (CEAM 40.CA
NO.5 SLACKEYES) 4
PUIPKINS (12 VARIETIESINCLUDING MILLED
BIG MAX AND KING OF MAMMOTHS)
BUSH BEANS (? vfrVAFrES. MOSTLY 4
ASTRO)
SQUASH (EARLY WHITE SCALLo S) 4
TURNIPS (PURPLE TOP) 4
WILD HOSTS
BAHIA GRASS


'p


Vi~&.


Y-i.


S PLANTED

CA. PERiOD
/ lai WHEN FIRaT
FLOWER ING
STARTED



197 JF JJ OND JA
ADJ F A AMJ J ASO ND J F M A J J A SI


Fig. l.--Crop rotation within an 8-acre cropping

system near Quincy, FL.


I I I


Y u,








S--
.. .



1
" m imm f-ih i









The other crops were also generally in aoo.d condition diirin. much

of the study period, but at times were of a thin stand, droug:!i-stressed,

weedy, or diseased. Much of the white clover top growth died during

July and August of 1972, but it was lush again in September. The 1972

fall "volunteer" crop of cigar-wrapper tobacco was poor, consisting of

< 100 tobacco plants on 1/2 acre. As a result, this "crop" consisted

mostly of wild hosts. Similarly I obtained a poor stand in the fall

planting of tomatoes in 1972 and there were < 1000 plants per acre. I

also had trouble in obtaining a thick stand of millet in 1973; therefore,

it was quite sparse relative to the 1972 crop. Thorny pigweed, Amaranthus

spinosus, was not kept under control in the 1973 crop of tomatoes, pea-

nuts, and bell peppers. In addition to the weed problem, the 1973 crop

of bell peppers also became diseased, and much fruit rotted.

The crops selected for the 8-acre cropping system were mostly those

normally grown in fields and gardens in the northern Florida area, except

for grain sorghum, and pumpkins. Soybeans and cigar-wrapper tobacco have

been important commercial field crops in the Quincy area and collards

have been common in gardens.

Crops were generally grown during periods in which they are com-

monly grown in northern Florida. Production practices were similar to

those of an average farmer or gardener, except that no commercial chemi-

cal insecticides, nematicides, or fungicides were used. A ton per acre

of dolomitic lime was, however, applied in the winter of 1972. Also,

all crops except white clover were fertilized with inorganic fertilizer,

and a herbicide Lrogr=.m was followed in many crops. Generally 40-80 lb

of nitrogen and 40-120 lb of phosphoric acid and potash were applied to










the various crops,with tobacco and tomatoes receiving the heaviest
2
applications. Tobacco, corn, and grain sorghum were also side-dressed

with 40-120 lb of nitrogen when they were 1-2 ft in height. Collards,

cabbage (in 1973), soybeans, okra, tomatoes, field peas, bell peppers,

peanuts and bush beans, were given a pre-emergence treatment of 0.5-1.0

lb (AI per acre) trifluralin; tobacco was given a pre-emergence treat-

ment of 0.75 lb (AI per acre) benefin; squash was given a pre-emergence

treatment of 0.5 lb (AI per acre) nitralin; and cabbage (in 1972) was

given a post-emergence treatment of 2.0 lb (AI per acre) of alachlor.

Crops were usually irrigated from an overhead sprinkler system when

necessary in order to follow "normal" crop production practices. Tobac-

co was irrigated more frequently than other crops.

Crops were removed from the system by mowing (i.e., rye, wheat,

cabbage (in 1972), tobacco, corn, grain sorghum, okra, and millet)

and/or turning them under with an offset disc harrow. Some fruit were

harvested in some crops (e.g. okra) to prevent termination of growth.

Also blooms were topped 2-3 times per crop in tobacco and collards.

Of the imrT:diate area (i.e., ca. 3 miles) surrounding the 8-acre

cropping system, about half was forested. Another large portion was

covered with volunteer vegetation, bahia grass, rye, or millet during my

studies in the system. However, there were also 2 cigar-wrapper tobac-

co shades ca. 1/2 mile from the 8-acre system, which did contain a total

of ca. 20 acres of tobacco during both 1972 and 1973. Also more than

100 acres of soybeans were growing 1-2 miles from the system, a small



"ToLacco" will be used when referring to both flue-cured and
cigar-wrapper tobacco.

"Corn" will be used when referring to both field corn and sweet
corn.









garden possessing collards was located within 200 ft of the system,

and there were several patches of field corn within 2 miles of the sys-

tem.


Whole plant inspections, sweeps, and plant shakes

The 8-acre cropping system was primarily monitored for eggs, larvae,

and/or adults of Plusiinae and Heliothis spp., as well as by certain

other pest species, and predaceous arthropods, by inspecting the whole

portion of the plants above the ground in 3 to six 0.001-acre sections

of row (10.9 or 13.6 row-ft) in most crops. Plants were generally

inspected 1-2 times a week; during several weeks more samples were taken

in some crops. In broadcast or drilled crops (white clover, rye, wheat,

millet, and sorghum (in 1973)), whole plant inspections were made on

0.00025 acre sections (1 ft x 10.9 ft). Samples were taken in a diagonal

pattern across each crop.

Sweeps with a net, 15 inches in diameter, were also used as a

sampling device in white clover, rye, wheat, millet, sorghum, and occa-

sionally in other crops. Thece samples usually consisted of 3-6 repli-

cates of 25 sweeps. In soybeans, some samples from the standing crop

were shaken onto a cloth between the rows (Boyer and Dumas 1963). These

were similar in replication and size to whole plant inspections. On a

few dates in the fall of 1973, counts of insects per plant were taken on

the sparsely populated stands of cigar-wrapper tobacco and tomatoes.

Sampling was initiated shortly after a good stand of the crop emerged

and was usually continued weekly until the crop was destroyed. However,

pumpkins were only sampled during 2 weeks (September 10 and 24). Also

samples from white clover, rye, wheat, and millet in 1972 were mostly

taken with the sweep net.









Collections of immatures

Eggs and larvae of Plusiinae, Heliothis spp., and various other

insects were collected in whole plant inspections, sweeps, plant shakes,

and some additional searches in the 8-acre cropping system. Eggs of

various pest species were collected on masking tape while taking whole

plant inspections, and trapped with transparent tape within holes in

cardboard paper by the method described by Hoffman et al. (1970). Lar-

vae were also collected, and were placed on a synthetic cabbage looper

(modified from Henneberry and Kishaba(1966)) or tobacco budworm (modified

from Berger 1963) diet contained in a 4-dr clear, paper-capped, plastic

cup.

Estimates of individual larval size were made in the field. "Small"

larvae were ca. <0.4 in. (or <1 cm), "medium" larvae were ca. 0.4-0.8 in.

(or 1-2 cm), and "large" larvae ca. >0.8 in. (or >2 cm).

Larvae of Heliothis spp. were identified to species in the labora-

tory at some time after they reached the 3rd instar. Plusiinae were

identified only after they became adults.

Even though all eggs (Peterson 1964) and larvae (Crumb 1956) were

determined to be Plusiinae, Heliothis spp., or otherwise, no eggs were

positively identified to species; and, many larvae of Heliothis spp., and

all larvae of Plusiinae that were parasitized or diseased, were not

positively identified to species. In most of the crops in which cabbage

loopers, soybean loopers, and tobacco budworms were found, almost all the

larvae or adults of these pests which were collected and identified,

belonged to only 1 Plusiinae species or 1 Heliothis species. Therefore,

when eggs or larvae are discussed in the various sections of this thesis,









they are usually labeled as the major species found in the ccp, with

qualifications made when necessary.


D-vac samples

In addition to the counts in the field, predaceous species were

sampled weekly from ca. 0.01 acre in triplicate (sometimes more) from

each crop in the 8-acre cropping system and from wild hosts in or adjacent

to the system with a suction sampler (D-vac ) similar to the one de-

scribed by Detrick (1961), and then were counted in the laboratory. One-

hundredth of an acre was 109 row-ft for crops with 4 rows per 16 ft,

136 row-ft for crops with 5 rows per 16 ft, and 2 x 219 ft in broadcasted

and drilled crops (see Fig. 1). Arthropods caFtured during the D-vac

sampling were retained in nylon organdy bags, placed in ice chests, trans-

ported to the laboratory, and processed through Tullgren funnels. In

1972 all crops of the 8-acre cropping system were sampled in this manner.

However, in 1973, cabbage, peanuts, field peas, and bell peppers were

not sampled with the D-vac.


Wild Hosts

In addition to D-vac sampling, other methods were used to sample

wild hosts growing on roadsides, as well as some near and within the

8-acre cropping system. Most samples were obtained during the fall of

1972 and spring and summer of 1973. Sampling was primarily with asweep

net but some random inspections of plants were also made. All larvae and

eggs of Plusiinae and Heliothis spp. found were collected and handled as

previously described.

The complex of volunteer plants sampled consisted primarily of dog

fennel, Eupatorium spp.; ragweed, Ambrosia artemisiifolia; prickly sida,










Sida spinosa; crimson clover, Trifolium incarnatum; and various grasses

(probably mostly bahia grass) in the roadside area adjacent to the sys-

tem; and thorny pigweed, crabgrass, Digitoria spp.; and nutsedge, Cyperus

spp. within the system. Some other wild hosts from which samples were

taken were hop clover, Medicago lupulina; sicklepod, Cassia obtusifolia;

camphor plant, Heterotheca subaxilaris; goldenrod, Solidago spp.; pepper

grass, Lepidium virginicum; toadflax, Linaria canadensis; dock, Rumex

hastatulus; crotolaria, Crotalaria sp.; johnsongrass, Sorghum helepense;

kudzu, Pueraria lobata; cocklebur, Xanthium pennsylvanicum; beggarweed,

Desmodium tortuosum; smallflower morningglory, Jaquemonta taminifolia;

Venus lookingglass, Specularia perfoliata. and vervain, Verbena tenuisecta.


One-Acre Shade

Additional experiments were conducted in a 1-acre cigar-wfapper

tobacco shade (232 x 192- x 9 ft) covered with loosely woven cotton cloth
2
of 8 x 10 threads per in. except for several holes in the ceiling cloth

which could not be patched. 'Astro' bush beans, 'Florida 20' cigar-

wrapper tobacco, 'Hampton' soybeans, 'Vates' collards, 'Early Round Dutch'

cabbage, 'World Beater' bell peppers, and 'Homestead' tomatoes were

planted (Table 1) in 5 to ten 200-ft rows spaced 3 ft apart from center

(Fig. 2).

Visual inspections during the experiment for amount of foliage and

extent of insect, disease, and weed damage to the crops, indicated cab-

bage and tobacco were in the poorest condition. The foliage of soybeans

was in the best condition followed by bell peppers, bush beans, collards,

and tomatoes. It was necessary to apply a short residual insecticide,

mevinphos, at 1.5 lb AI per acre, to prevent extensive insect damage to











Table l.--Schedule of cultural practices and of releases of cabbage
looper, soybean looper,and tobacco budworm in a 1-acre tobacco shade,
Quincy, FL, July-September, 1971.




Date Crop treatment Rate/acre Crop


Cultural practices


Planting (Seedlings)
Planting (Seeds)
Planting (Seedlings)

Planting (Seedlings)
Fertilizer 6-12-12
and
36-0-0

Fertilizer 6-12-12
Cultivation
Herbicide DCPA

Insecticide Mevinphos


budworm
looper
budworm
budworm
looper
budworm
looper
looper
budworm
looper


1000 lb
and
50 lb

200 lb

10 lb

1.5 lb


Moth releases

30
30
82
30
30
30
30
100
350
100


Bell pepper, tomato
Soybean
Collard, cabbage, cigar-
wrapper tobacco

Bell pepper, tomato,
collard, cabbage, cigar-
wrapper tobacco, bush
bean
Soybean
All crops
Bell pepper, tomato,
collard, cabbage
All crops


All
It

II
gI
I,




t,
It
to
"t
to


crops
it



it
i,

Ut
"I
"I


aAdult o and o pairs (1-3 days old).
+


Jun. 23
July 1
Jul. 6,7

Jul. 10
Aug. 3







Aug. 5

Aug. 6


Aug. 15

Aug. 19
Aug. 20

Aug. 25


Aug.
Sep.
Sep.


Tobacco
Cabbage
Tobacco
Tobacco
Cabbage
Tobacco
Cabbage
Soybean
Tobacco
Soybean





11




















TOMATOES



BELL PEPPERS



CABBAGE
189
ft
COLLARDS


SOYBEANS




BUSH BEANS **

199 ft
= 9 rows
** =10 rows
*** = 5 rows







Fig. 2.--Crop layout in a 1-acre tobacco shade,
Quincy, FL, July September, 1971.









the crops prior to beginning the experiment (Table 1), and in August a

pathogen caused "black rot" in the developing heads of cabbage. Also,

the tomato plots became infested with thorny pigweed.

The area immediately surrounding the shade was covered with volunteer

vegetation. Also there were several other cigar-wrapper tobacco shades

containing tobacco near the 1-acre shade.

Numbers of eggs and larvae of Plusiinae, Heliothis spp., and several

other insect groups were estimated in each crop from 5 to 10 whole-plant-

inspection samples in 5- to 10-ft sections of row in all crops except

cigar-wrapper tobacco. On cigar-wrapper tobacco, samples were always made

twice as large (10- to 20-ft sections of row) as those in other crops

because of the sparse stand.

Eggs and larvae of lepidopterous species were collected and identi-

fied as was described for the 8-acre cropping system except that only

tobacco budworm diet was used. Eggs, and parasitized or diseased larvae

of some Heliothis spp. and all Plusiinae, were not positively identified

to species. Therefore, as in the 8-acre cropping system, names used in

discussion of those groups in the Trichogramma pretiosum (Riley) and

Chrysopa carnea Stephens release sections are those of the major groups

known to be present based on identified samples.

Two hundred row-ft were sampled with a D-vac in each crop for an

additional monitor on predaceous arthropod populations. Techniques used

were similar to those previously described for D-vac sampling.

Data on weather conditions prevailing during the periods of obser-

vation in the 1-acre shade, and the 8-acre cropping system, were obtained

from the weather station of the National Weather Service, NOAA, located

at the Agricultural Research and Education Center, IFAS, Quincy, FL.















SECTION II

SEASCi-.L AB'UL7 ANCF AND
HOST PREFERENCE


Knowledge of seasonal abundance of pests such as the cabbage looper,

soybean looper, and tobacco budworm, in the various areas where they occur,

is fundamental to developing an understanding of the population dynamics

of these pests (Anonymous 1969). Methods for predicting economic infes-

tations of these pests, and schemes for subsequent manipulations to limit

their densities can not be developed and/or perfected until such informa-

tion is obtained.

Thus, information on seasonal abundance of the 3 noctuids should

allow better employment of existing technology for prediction, prevention,

and suppression of potentially damaging infestations, as well as stimulate

development of new mechanisms for prediction, prevention, and suppression.

Host preferences of a particular pest and the availability of suit-

able and preferred hosts are intricately related to the seasonal abundance

characteristics of the pest. Although the cabbage looper, soybean looper,

and tobacco budworm appear to prefer certain hosts, infestations in crops

other than their "namesake," or other common hosts, occur quite frequently.

For instance, for the period of 1970-1972 cabbage looper infestations

were reported in tobacco, soybeans, tomatoes, bell peppers, bush beans,

southern field peas, turnips, spinach, celery, cantaloupe, potatoes,

alfalfa, and roses and other field grown flowers (Anonymous 1971a, 1972a).

Similarly, the soybean looper infested bush beans, bell peppers, cole









crops, cotton, potatoes, celery, and field grown flowers (~r:on~riou 1971a,

1972a),and substantial infestations of the tobacco hudwor- were reported

to have occurred in soybeans and pigeon peas (Anonymous 1971a, 1972a).

Obviously infestations of the cabbage looper, soybean looper, and tobacco

budworm occur quite frequently on host plants other than their most well-

known hosts and these so-called "alternate hosts" probably have a great

influence on the population dynamics of the different species. Therefore,

an increased knowledge of host preferences of these species should help

in understanding and anticipating infestations on various hosts, and help

in developing management schemes to prevent or limit infestations on some

selected hosts.

Therefore, the purpose of the studies reported in this section were

(1) to determine seasonal abundances of cabbage looper, soybean looper,

and tobacco budworm, and evaluate density prediction capabilities as

measured with various sampling techniques (in an 8-acre cropping system

in northern Florida); and (2) to determine the relative abundance and

host plant preferences of these pests with a special emphasis on domestic

crops grown in northern Florida.


Literature Review


Seasonal Occurrence and Abundance

Cabbage looper

The cabbage looper has been reported on 119 host plants (Sutherland

1965). It has been collected from some host plants growing in the wild

including wild crucifers and wild tobacco, Nicotiana glauca (McKinney

1944), lambsquarters, Chenopodium spp. (Crumb 1956), and ground ivy,

Glechoma hederacea, wild radish, -.phar.-; raphanistrum (Sutherland 1966),









and several other wild hosts (Sutherland 1965). In his studies, Sutherland

(1966) could not find it on wild crucifers in New York in the spring;

however, he may not have allowed adequate time for detectible numbers to

increase on these hosts before he began sampling.

Sutherland (1966) found from laboratory, insectary, and field studies

that the cabbage looper can successfully develop on a wide range of hosts

including cabbage, collards, tomatoes, bush beans, peppers, squash, and

turnips, but that development was slow on some hosts such as peppers. In

a caged test, survival of cabbage looper was better on cabbage and tomatoes

(71 and 70%) than potatoes, lima beans, lambsquarters, and peppers (57-32%).

From laboratory studies, Shorey et al. (1962) found, however, that the

cabbage looper can develop more rapidly on lima bean foliage than on

cabbage foliage.

Despite the fact that the cabbage looper has been reported to develop

on a number of host plants, cultivated and wild, it appears to favor cul-

tivated crucifers over other hosts. Host preferences of the cabbage looper

will be discussed more thoroughly in later sections dealing specifically

with that subject.

From observations of cabbage looper immatures that occurred on some

of its "favored" hosts in various parts of the U.S., varying numbers of

generations per year have been reported (Sutherland 1965). For instance,

McKinney (1944) believed 5-7 occurred per year in Arizona, Quaintance

(1896) reported 6 for Florida, and Britton (1933) reported 2 occurred in

Connecticut. Most recent reports indicate that the cabbage looper can

occur mostly year-round in the southern areas of the U.S., but that it

is limited to a short growing season in the north.

Cabbage loopers have either been absent or at low densities during









the winter in most studies on seasonal occurrences. It can overwinter

in parts of South Carolina (Reid and Bare 1952), Louisiana (Smith and

Brubaker 1938), Texas (Wolfenbarger 1967), Arizona (McKinney 1944), and

California (Oatman 1966). Studies by Endris (1973) indicated that the

cabbage looper could overwinter in northern Florida; in the winter of

1972-73, it overwintered and ri;rcd:ce5 on St. George Island in northern

Florida (Lingren personal communication). However Mitchell (1973b)

thought it likely that the cabbage looper reproduced and developed through-

out the year only in southern Florida. In contrast it has even been pro-

posed that cabbage loopers might overwinter in the extreme northern U.S.

(Sirrine 1899; Dustan 1932; Huckett 1940). However, Sutherland (1966) in

New York, Hofmaster (1961) in Virginia, and Elsey and Rabb (1970) in

North Carolina found from their observations it did not overwinter in

these areas. In view of the conflicting reports it is likely that the

overwintering range of the cabbage looper varies with the severity of

the winter.

The abundance of the cabbage looper on various hosts occurring in the

winter and other seasons has been reported for a number of areas of the

U.S. (Greene 1973). 'Densities reported varied greatly of course because

of changes in regions, weather conditions, hosts sampled, cultural prac-

tices, sample size, and other factors; and Greene (1973) pointed out that

host plant density as well as maturity and host preferences would affect

the real area abundance or potential abundance for various cabbage looper

(sub)populations reported.

Reports on seasonal abundance of the cabbage looper in south or mid-




P. D. Lingren, Cotton Insects Res. Laboratory, Agr. Res. Serv.,
USDA, College Station, TX.









Florida (Wilson 1957; Poe 1972; Strar.dberg personal comrLunication2), south

Texas (Wolfejbarger 1967), Arizona (McKinney 1944), and southern California

(Oatman 1966; Oatman and Platner 1969, 1972) show that the cabbage looper

can occur at high densities early in the spring and late in the fall. In

these areas it is often at high densities on cabbage, lettuce, tomatoes,

and some other crops during March-June and August-December. As far north

as South Carolina, Reid and Bare (1952) found major peaks of cabbage

looper in cabbage during September, November, and May.

Farther north Hofmaster (1961) found the highest numbers of cabbage

loopers occurred on cabbage during August, but none could be found by late

October. Similarly, Wieres and Chiang (1973) found in some Minnesota

cabbage, highest densities of the cabbage looper occurred in August with

very low densities by mid- to late September. In New York, Sutherland

(1966) found few cabbage loopers after Septanbc-r, and the earliest date.

they were detected was June 14. Even farther north in eastern Ontario,

Harcourt et al. (1955) found that cabbage loopers did not occur until late

in the cabbage-growing season, and even then were rarely found.

One of the earliest seasonal abundance studies dealing with the

cabbage looper occurred in Louisiana in an area at a similar latitude as

Quincy, FL (Smith and Brubaker 1938). Highest density of larvae found on

cabbage sampled September to May was 11.98 per plant in early November..

Finally, some of the most extensive studies on seasonal abundance of

ijmatures of the cabbage looper took place in southern California (Oatman

1966; Oatman and Platner 1969, 1972). In successive plantings of cabbage


2Letter dated November 13, 1973 from J. O. Strandberg, Agr. Res. and
Educ. Center, Univ. of Florida, Sanford, FL.









sampled from April, 1963 to April, 1965 (Oatman and Platner 1969), the

greatest densities of eggs of cabbage looper (4.6 and 2.6 per plant)

occurred in September and October of 1963 and 1964, respectively, and the

lowest densities (0/plant) occurred in January. Major peaks in egg den-

sities also occurred in May, August, and November. Also, larval numbers

were highest in September and October (9.5 and 4.1 per plant), but other

major larval peaks occurred in May, June, August, November, and December.

Larval densities were lower from January through April than during other

periods of the year.

In lettuce in southern California, Oatman and Platner (1972) found

mostly low densities of the cabbage looper. Peak numbers of eggs and

larvae occurring on lettuce for the growing season of November, 1966 to

January, 1967 were 0.36 per plant and 0.28/plant, respectively. For the

growing season from Novemoer, 1967 January, 1968, peak egg and larval

numbers were 0.82 and 0.60 per plant, respectively.

In his review, Greene (1973) suggested the need to relate seasonal

abundances of immatures of the cabbage looper on cash crops, to adult

cabbage looper capture data, in order that the relatively easy adult

sampling techniques might be perfected somewhat, and utilized in

predictiveschemes. Falcon et al. (1967a, b) felt that blacklight (BL)

trap information could be utilized for effectively predicting infestations

of cabbage loopers in cotton and assessing population trends of the

cabbage looper. Similarly, in studies ir northern Florida (Greene 1971)

and central Florida (Strandberg personal communication) there seemed to

be a positive correlation of BL trap captures of adult cabbage loopers

with cabbage looper eggs in the field. Also, basic work on a mathematical

a'odel for describing cabbage looper behavior in relation to light traps








has been reported by Hartstack et al. (1971). However to date trap

catches of adult cabbage loopers has not been developed to the point

where they can be utilized consistently for predicting immature numbers

on crops.


Soybean looper

Soybeans and cotton have been two of the most commonly reported hosts

of the soybean looper (Anonymous 1971a, 1972a), but few studies have been

conducted on seasonal occurrence and abundance of scybean looper on any

host. However, Burleigh (1972) did report that the soybean looper com-

pleted 4 generations per year on soybeans in Louisiana. Also, Endris (1973)

found that it could survive the winter as far north as Gainesville, FL.

The only major study on seasonal abundances of immatures of the soy-

bean looper was conducted by Burleigh (1972) on soybeans for 2 years in

3 different "agro-ecosystems." In this study, larvae were found from

June through September, with maximum densities over 20,000 per acre

occurring in September in a "cotton agro-ecosystem," the system which

received the heaviest insecticide treatment. Lower densities were re-

corded in a "cleared hardwood agro-ecosystem" with lowest larval densities

occurring in a "rice agro-ecosystem." High peaks of larval densities

generally occurred in late August or early September in all systems, but

in 1 year densities were highest in early July in the "rice agro-ecosystem."

In addition to Burleigh's report on seasonal abundances the soybean

looper has been reported to occur in sweet corn in late May and June in

south Florida (Janes and Greene 1970), in various crops, May-October

in Alabama (with highest numbers in August and September) (Canerday and

Arant 1966), in sunflowers in October near College Station, TX (Teetes

et al. 1970), and at high densities in soybeans in Alabama (Harper and









Carner 1973) and South Carolina (Carner et al. 1974) during late August

and September.

In the sunflower study, densities as high as 52,320 per acre were

reported (Teetes et al. 1970). The sunflowers of Teetes et al. (1970)

occurred in an area with high acreages of cotton, and Jensen et al.

(1974) showed that nectar from cotton utilized by soybean looper adults

might increase the potential for outbreaks of this pest.

Mitchell et al. (1975) reported on seasonal abundance of soybean

loopers captured by synthetic sex pheromone baited BL traps, but did

not relate them to immature occurrence and abundance. They found no adult

activity in a northern zones, where mean winter temperatures are often

below 100C, and that adult activity was significant in a southern zone

(most of Florida) where mean winter temperatures exceeded 12.60C. They

concluded that the soybean looper survives the winter in Florida, increases

there in the spring, moves northward into Georgia and South Carolina in

the summer, and then migrates southward in late September and October.

Prediction of occurrence of the soybean looper in its preferred crops

might be achieved by using adult capture data. However, the feasibility

of such techniques his not been documented.


Tobacco budworm

Similar to the cabbage looper, the tobacco budworm has been found

from a number of hosts (Chamberlin and Tenhet 1926b; Barber 1937; Brazzel

et al. 1953; Snow and Brazzel 1965; Snow et al. 1966; Neunzig 1969; Teitz

1972; Lincoln 1972); however, wild hosts appear to be more important in

the development of tobacco budworm populations than in the development

of cabbage looper populations. Tobacco and cotton appear to be the

favored cultivated host, with tobacco apparently usually favored over








cotton when both are available (Lincoln 1972). Host preferences will be

covered in more detail in later sections.

Although tobacco budworm probably migrates over considerable dis-

tances, and it does normally go into diapause in the pupal stage in the

fall in order to overwinter, it appears to be limited to a southerly

range. This may be largely due to a southerly range of its favored hosts.

However, there is, of course, considerable variations in seasonal occur-

rence and abundance of the tobacco budworm within its range in the U.S.

Neunzig (1969) found that the tobacco budworm emerged from diapause

in North Carolina during a period from late April through early May. Lincoln

(1972) concluded "eggs are first found in April in central Texas, central

Mississippi, and southern Arkansas. Thereafter, larvae are continuously

present through October." In extreme south Texas, the tobacco budworm is

active throughout the winter (Fife and Graham 1966; Graham and Robertson

1970) and probably goes through several generations per year.

Chamberlin and Tenhet (1926b) found that 5 generations occurred per

year in northern Florida, but that the tobacco budworm was not active

after October. Further north, Neunzig (1969) concluded that it was

capable of completing only 4 generations per year in North Carolina.

Since its range in the U.S. appears to be more limited than the

cabbage looper, season occurrence and abundance of the tobacco budworm

seem to be more dependent on available favorable host plants than on

favorable climatic conditions. Lincoln's (1972) discussion of the prob-

lem of determining the seasonal abundance of the tobacco budworm is also

applicable to the cabbage looper and the soybean looper. He said that

although the tobacco budworm is strongly influenced by the availability

in sequence of favorable hosts, "populations are difficult to quantify.









Infestations are found on many different species of plants, including

uncultivated ones. Sampling the assorted hosts to obtain comparable

data is hardly possible. Estimating acreage of a weed in mixed and

scattered stands cannot be done accurately. Some hosts may be heavily

infested, but contribute little to population buildup because of

parasitism, predation, or nutritional inadequacy of the host."

Major hosts for the 1st (spring-early summer) generations of the

tobacco budworm include wild hosts such as crimson clover (Brazzel et al.

1953; Snow and Brazzel 1965); wild tobacco, Nicotiana repanda; Verbena

neomexicana (Graham et al. 1972); toadflax (Barber 1937; Neunzig 1963,

1969); and Carolina cranesbill, Geranium carolinianum (Snow et al. 1966);

and cultivated hosts such as tobacco (Chamberlin and Tehnet 1926a;

Neunzig 1969) and tomatoes (Graham et al. 1972). Minor hosts have in-

cluded white clover, vetch (Lincoln 1972), Verbena bipinnatifida,

Solanum eleagnifolium, Gaura parviflora, Malvaviscus drummondii (Graham

et al. 1972), and persian clover (Snow and Brazzel 1965).

For mid-season (summer) generations the cultivated hosts, tobacco

(Brazzel et al. 1953; Snow and Brazzel 1965; Neunzig 1969) and/or cotton

(Brazzel et al. 1953; Snow and Brazzel 1965; Neunzig 1969; Graham et al.

1972) serve as major hosts of the tobacco budworm although okra, tomatoes,

and alfalfa (Lincoln 1972) may also be important. Wild hosts, including

hop clover (Snow and Brazzel 1965), toadflax (Neunzig 1969), deergrass,

Phexia spp. (Barber 1937; Neunzig 1963, 1969), and Ruellia runyonii,

Rumex sp, Passiflora foetida, Schrankia latidens and Ratibida columnaris

(Graham et al. 1972), generally had very low densities of tobacco budworm

during mid-season.

For the late season (late summer-fall) generations of tobacco bud-

worms, a complex of wild hosts appear to be very important. Eeagarweied,









Desmodium spp. (Barber 1937; Snow and Brazzel 1965); deergrass (Neunzig

1969); and R. runyonii (Graham et al. 1972) appear to be major hosts in

some areas, but tobacco budworms are also found on small flower morning-

glory (Brazzel et al. 1965); spider-flower, Cleome spinosa; Haplopappus

divaricatus (Snow and Brazzel 1965); Abutilon trisulcatum; P. foetida;

Dalea pogonathera (Graham et al. 1972); and morningglory, Ipomaea

trichocarpa (Lincoln 1972). However, development of later generations

on cultivated hosts such as okra (Snow and Brazzel 1965), tomatoes,

squash (Graham et al. 1972), late or 2nd-growth cotton, soybeans, and

alfalfa (Lincoln 1972) may be just as important as development on the

wild host complex, or more so.

As was pointed out by Lincoln (1972), it is very difficult to relate

seasonal abundances reported from one area to another and from one host

to another. Graham et al. (1972) did attempt to determine the area

covered by many of the hosts of tobacco budworms in their study area in

south Texas and attempted to determine densities of tobacco budworms

occurring in the various hosts. They reported highest densities of

tobacco budworm larvae occurred in wild tobacco (at a peak of 0.45 per

plant) and tomatoes (*at a peak of 0.22/row-ft) during the spring (early

and late May). After early June and during the summer larvae were com-

monly found at densities greater than 0.2 per row-ft in insecticide-

treated cotton. Densities were similar in tomatoes and squash during

the fall.

During the spring in northeast Mississippi, another cotton-producing

area, highest densities of the tobacco budworm were found in crimson

clover and Persian clover (Snow and Brazzel 1965). Densities peaked at

16 larvae per 100 sweeps in crimson clover and 40 larvae/100 sweeps in

Persian clover in early May.









During tfLe spring and summer in North Carolina tobacco, number of

tobacco buwqcrm larvae fluctuated from ca. 0.30 per plant to 1.00/plant

(Neunzig 1969). Major peaks in densities occurred during most months from

May through Sapteir-r with maximum numbers found in August.

In the early part of this century Chamberlin and Tenhet (1926b) con-

ducted studies on the seasonal abundance of the tobacco budworm near

Quincy, FL, close to where the study presented herein was undertaken. In

cage studies they found tobacco budworms emerging in the spring from April

28 to June 11. However, in some seasons they found tobacco budworm eggs

in tobacco seed beds during March. They felt there were 5 generations

of the tobacco budworm in northern Florida, with the Ist and 2nd genera-

tions developing on tobacco, the 3rd on tobacco and beggarweed, and the

4th and 5th during September and October on heggarwead. Chamberlin and

Tenhet (1926b) reported that although tobacco bud'!.or-is were pests of okra

on the Virgin Islands, they were rarely found on okra growing near Quincy.

Also only a few were found on tomatoes.

An extensive research effort to relate seasonal abundances of immature

Heliothis spp. and adult trap capture data has been made by Hartstack et

al. (1973) in a Texas cotton-produ=ing region.. In their attempt to survey

the population dynamics of the tobacco budworm, they reviewed pertinent

literature on this subject and found that only a limited amount of work

had been done tnat was useful in estimating and predicting infestations

of tobacco budworms on various crops with adult trap information.

Since the review of Hartstack et al. (1973), however, Hendricks et

al. (1973) found that saucer-type pheromone traps detected low levels of

the tobacco budworm better than BL traps. And in more extensive studies

in South Carolina, Roach et al. (1975) verified this. Both Roach et al.









(1975) and Hendricks et al. (1973) found that BL trap catches are generally

inversely proportional to pheromone trap catches. This indicates that at

high densities, pheromone traps may not be effective because of competition

from native females.

Hartstack et al. (1973) found that probably 70% of the tobacco bud-

worms in the Brazos bottom near College Station, TX, emerged from March

10 to April 30,. and that the mean rate of increase (actually the popula-

tion trend index (I)) calculated from accumulated BL trap catches was

1.40 from April 30 to July 9, and 5.75 from July 9 to September 17. They

found "rates of increase" were reduced by as much as 80% on nights of the

full moon during June, July, and August. Tobacco budworm captures were

very low in April and May, but increased rapidly from June, and peaked

in September (Hartstack et al. 1973). Catches decreased in October and

none were caught in November. Most tobacco budworms were caught in traps

placed near cotton.

The data collected by Hartstack et al. relating to estimation of

numbers of adults of Heliothis spp: generation development time, rates

of increase, and host affinity was used to develop a predictive model

for Heliothis spp. This model has "provided encouraging results when

used for predicting when and how large the next generation of Heliothis

spp. adults might be." However, the model of Hartstack et al. (1973)

was primarily for corn earworm, Heliothis zea (Boddie) rather than

tobacco budworm. A great deal more knowledge about the tobacco budworm

needs to be acquired before a reliable predictive model can be developed

for this species.









Host Preference

Cabbage looper

As has been discussed previously, it is generally believed that

domestic crucifers are preferred hosts of the cabbage looper but a wide

range of host plants (at least 119), including several wild hosts, have

been reported for the species (Sutherland 1965). Even though many host

plants for the cabbage looper have been identified,little information is

available that establishes host plant preferences of the species. How-

ever, host preference studies by Elsey and Rabb (1967) indicated that the

cabbage looper preferred collards over tobacco as sites for oviposition.

In other host preference studies in field cages, cabbage loopers pre-

ferred cotton and collards as oviposition sites when these crops were

compared with broccoli, cauliflower, or cabbage (Boling and Pitre 1971).

Other information on host preference of the cabbage looper can be

gleaned from various investigations of host plant resistance of some

crucifers to cabbage looper infestations. In these studies some species

of crucifers seemed to be preferred over others for oviposition sites

(e.g. collards, broccoli, and cabbage). However, results were usually

confounded by the variability of the physical condition of the plants

used (Harrison and Brubaker 1943; Radcliffe and Chapman 1966; Sutherland

1966).


Soybean looper

Soybeans have been reported as the primary host for the soybean

looper in Louisiana (Hensley et al. 1964) and Alabama (Canerday and Arant

1966). But in these and other areas, major infestations have been re-

ported on other crops. The soybean looper has been reported as a pest

of peanuts in Alabama (Canerday and Arant 1966), sweet potatoes and cotton








in Alabama and Louisiana (Hensley et al. 1964; Canerday and Arant 1966),

sweet corn in southern Florida (Janes and Greene 1970), and floricultural

crops in southern California (Morshito et al. 1967). Tomatoes (Canerday

and Arant 1966), tobacco, collards, beans, lettuce, alfalfa, wandering-

Jew, Cormmelina spp.; Croton capitatus (Crumb 1956); goldenrod, Solidago

sp.; Geranium sp. (Eichlin and CunninrghaE 1969); and guar (Teetas et al.

1970) have also been reported as soybean looper hosts. Furthermore,

Fuchs et al. (1973) found that 11% of the Plusiinae in some of their

cabbage plots were soybean loopers. However, although these and other

hosts have been reported for soybean looper, no specific studies have

been reported on host preferences.


Tobacco budworm

Tobacco and cotton are major host plants of tobacco budworm, but it

also attacks tomatoes, soybeans, and many other crops and wild hosts

(Lincoln 1972). Teitz (1972) listed 31 hosts that have been reported for

tobacco budworm. Many studies in various regions of the U.S. have been

conducted on the host plants of tobacco budworm and of the seasonal

occurrences of Heliothis spp. on them. Most were reviewed by Snow and

Brazzel (1965), Neunzig (1969), and Lincoln (1972). These studies in-

dicate tobacco is the preferred host of the tobacco budworm.

Still, no specific studies of tobacco budworm preferences among

various crops have been reported. Greene and Thurston (1971) did point

out the preference of the tobacco budworm for certain species of tobacco,

particularly those with pubescent leaves and showing many protruding

trichomes. Another investigation, by Lukefahr and Shaver (1972), has

demonstrated differences in oviposition rates of the tobacco budworm on









certain lines of cotton. Plant characteristics such as the presence

or absence of extrafloral nectaries and pubescence, influenced preference

for or against a certain line.


Methods and Materials


Seasonal Occurrence and Abundance


Data on immatures of Plusiinae and Heliothis spp. were taken during

all seasons in all crops in the 8-acre crcFpi.n system, and during some

seasons in some other areas near the system, from December, 1971 to Septem-

ber, 1973. The techniques are described in Section I.

In addition, adult numbers were monitored with light and pheromone

traps. A baffled 15-w fluorescent blacklight (BL) trap (ca. 10-15 ft

above the ground) similar to that described by Har3irng et al. (1966), was

operated on the northeast and southwest ends of the 8-acre system, ca.

130-260 ft from the edges of the system (Fig. 1). BL traps were baited

monthly with 0.04 dr (0.15 ml) synthetic cabbage looper sex pheromone,

cis-7-dodecen-l-ol-acetate (cis-7-dda), dispensed from a 0.4 dr polyethylene

vial placed on the BL trap post, ca. 4 ft from the ground.

Cylindrical electric-grid traps (Kishaba et al. 1970; Mitchell et al.

1972) were placed at the north, east, south, and west corners of the system

(ca. 130-260 ft away). Opposite grid traps (e.g. N and S or E and W)

were generally baited with five (infrequently 10 to twenty) 2-to-3-day-old

virgin female cabbage loopers or tobacco budworms. Grid traps were baited

once a week (December 5, 1971-May 14, 1973), or at 3-4 day intervals (May

14, 1973-August 16, 1973).

Moths attracted to and capture by the traps were funneled into a

6 x 18 in. cylindrical vinyl basket containing a dichlorvos-impregnated









polyvinyl chloride strip. Moths were collected 2-7 times a week during

the study and brought into the laboratory and identified (Brazzel et al.

1953; Habeck 1968). Species of Plusiinae and Heliothis were counted and

sexed. The degree of mating of female cabbage loopers, soybean loopers,

and tobacco budworms was monitored by dissecting the bursa copulatrix

(Callahan 1958), and counting numbers of spermatophores.

Moon phases were obtained from U.S. almanacs for 1971, 1972, and

1973. Therefore, they are not indicative of true moonlight intensity

since cloud cover and other environmental factors affecting the moonlight

were not recorded. Also, there was a house (light source) near both BL

traps and a security light near the north grid trap.


Host preferences

In an initial experiment on host preferences, I released 90, 522,

and 200 pairs of 1 to 3-day-old moths of cabbage looper, tobacco budworm,

and soybean looper, respectively, in the 1-acre cigar-wrapper tobacco

shade (Fig. 2) during the period from August 15 to September 8 (Table 1).

Larger numbers of tobacco budworms and soybean loopers were released be-

cause of difficulty in establishing populations of these pests in the

1-acre shade. Moths were taken to the shade just prior to sundown in

1-gal containers and released ontothe crops while walking diagonally

across crops of the 1-acre shade.

After moth releases, populations of immatures of the test species

were sampled (Section I) on 19 dates from August 16 to September 22.

Estimates of larval densities were used to establish crop preferences.

Data on number of larvae of each test species found per 10 row-ft over

the 7 crops on all the sampling dates underwent an analysis of variance.








Differences in means were separated using Duncan's multiple range test

at the 1% level of probability.

In a 2nd experiment the oviposition preferences of the tobacco

budworm, soybean looper, and cabbage looper were determined for crops

tested in the 1st experiment, plus cocklebur. In this test, 2 plants of

each crop and cocklebur were translated at random in a 6 x 4 x 5 ft

cage enclosed witn screen wire; then adults of the test insects were added.

The plants were allowed to stabilize for 1 week before moth releases were

begun.

Cocklebur was added to the test because it is very common in the

Quincy area and Lingren (personal communication) had observed larvae of

some species of Plusiinae feeding on this plant in cigar-wrapper tobacco

shades. However, Kincaid (1960) had suggested cockleburs were a good

cover crop to grow in rotation with cigar-wrapper tobacco and the weed

has been allowed to grow in tobacco shades in the area.

In the small cage, tomatoes and cockleburs appeared to be in the

best condition with tomatoes possessing about twice as much foliage as

other host plants. Host plants other than tomatoes and cocklebur were

in about "equal" condition.

Moths were released into the small cage and egg counts taken as

follows: cabbage looper, 15 pair of 2- to 4-day-old moths released on

September 22 with egg counts taken 1, 3, and 6 days after release; soy-

bean looper, 10 pair of 1- to 4-day-old moths released on September 9 and

15, and 20 pair released on October 6, with egg counts taken 1, 2, 3,

and 5 days after the 1st release, 1, 2, 3, and 6 days after the 2nd

release, and at 2 days after the 3rd release; tobacco budworm, 30 and 15

pair of 3- to 5-day-old moths released on August 30 and Septermber 9,

respectively, with egg counts taken at 2 and 4 days after the 1st release








and 1, 3, 4, 6 and 9 days after the 2nd release. Adults of the soybean

looper and cabbage looper were added at different times so that their

eggs could be properly separated. Data on number of eggs of each test

species found per plant over the 8 hosts on all of the sampling dates

were analyzed as described for the 1-acre shade.

For the set of data presented for each test species from the 8-acre

cropping system, seasonal means of number of Plusiinae and Heliothis spp.

per acre were obtained from weekly estimates as described in Section I.

These weekly estimates were combined and seasonal means for the included

species obtained by applying percentile values corresponding to the species

composition as estimated for each season based on identified samples. Sea-

sonal means for the particular species were then averaged to obtain the

"means" reported herein.


Results and Discussion

Seasonal Occurrence and Abundance

Cabbage looper

The only crops in the 8-acre cropping system from which we identified

cabbage loopers were collards, cabbage, soybeans, flue-cured tobacco,

tomatoes, okra, and white clover (Table 2). Results indicated cabbage

looper larvae were found only during 8 of 49 weeks of sampling in crops

other than collards and cabbage and densities were almost too low to be

detected by the sampling procedure employed. (They were generally

estimated at less than ca. 700 per acre.)

Cabbage loopers were found in soybeans, tomatoes, flue-cured tobacco,

white clover, and okra in the spring. No cabbage loopers were found

from samples of wild hosts in any season.

Numbers of cabbage looper eggs and larvae estimated per acre in

collards and cabbage from March through May in 1972 and March through June














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in 1973, periods when cabbage was present in the system, are presented in

Table 3. Most cabbage loopers in the system were found on these 2 crops.

Estimates of eggs per acre in collards were significantly higher than

those in cabbage, but estimates of larvae/acre were similar. Since

collards were the most utilized host of cabbage looper in the 8-acre

cropping system in all seasons, the reported seasonal abundance of

immatures of this pest deals primarily with this crop.

Cabbage loopers were found in collards or adult traps of the system

during most months of the period studied (Fig. 3a). Few eggs, larvae,

or adults were found in the winter months and highest densities were

found during September, 1972 and June, 1973.

In 1972 there were at least 7 major peaks of eggs (over 1000 per

acre) in collards and eggs were estimated at over 10,000/acre during the

weeks of April 23, May 7-28, June 11, June 25, July 2, 9, and August 20-

September 17 (Fig. 4a). A peak egg density of ca. 41,170 per acre

occurred during the week of August 27. In 1973 (January-July 25) all 5

peaks of eggs in collards were estimated at over 1000 per acre and eggs

were estimated at 10,000/acre for the weeks of May 13-June 17 and July 8

(Fig. 4a). The highest egg density in 1973, amounting to 43,090 per acre,

*'ccur'_3 during the week of June 10.

Four peaks of large larvae at densities greater than 1000 per acre

occurred in 1972 and only 2 peaks above 1000/acre occurred in 1973 when

sampling was terminated in August. The highest densities were 2670 and

1880 per acre in 1972 and 1973, respectively (Fig. 4a). Densities of small

larvae (Fig. 4a) and medium larvae were generally intermediate to densities

of eggs and large larvae.


Eggs of Plusiinae or Heliothis spp. were not identified to species
but are generally labeled as being the major species identified in the
larval stage from a particular crop, as described in Section 1.










Table 3.--Relative number of immatures of cabbage looper in
collards and cabbage in an 8-acre cropping system during the spring
of 1972 and 1973.



Ca. no./acre

Date Collards Cabbage
(Week of) Eggs Larvae Eggs Larvae


1972


Mar. 5
12
19
26
Apr. 2
9
16
23
30
May 7
14
21
28

-a
x


0
60
630
130
0
11,160
2,500
13,420
22,160
14,830
10,500

6,490


560
620
250
2,580
2,620
160
3,830
7,370
6,830
5,000

2,980


0
0
0
0
1,080
1,670
5,340
4,010
9,830
7,500


2,940


0
0
240
0
830
1,000
1,840
4,560
6,920
6,670


2,206
2,206


1973


Mar. 18
25
Apr. 1
8
15
22
29
May 6
13
20
27
Jun. 3
10
17

-b
x


410
1,040
0
2,910
4,790
2,090
2,190
3,960
14,750
13,600
14,160
24,590
42,090
22,290

9,230


0
0
2,090
6,250
3,960
8,340
5,880
4,790
15,000
7,910
6,250
17,500

4,780


0
500
8,830
0
1,600
5,170
18,170
10,670
16,170

9,500


6,419


0
170
1,330
3,670
2,000
2,330
15,830
18,500
15,000
-
4,830


5,790
5,790


obtain means.


trom March 18 and June 3 were rot used to obtain means.


Data from March 5, 19, and ay 28 were not used to
Data from March 5, 19, and May 28 were not used to










A. rABBAGS LOOPER


1973


B SOYBEAN LOOPER


1972


C TOBACCO BUDWORM


197 1 9 73


Fig. 3.--Mean number of cabbage looper, soybean looper, and tobacco
budworm adults (mostly males) caught per blacklight trap baited with
synthetic cabbage looper pheromone, or electric grid trap baited with
virgin female cabbage looper or tobacco budworm /night compared with
mean number of eggs of Plusiinae or Heliothis spp. in preferred crops in
an 8-acre cropping system. Numbers of eggs found are plotted at the
middles of weekly periods; points for adult numbers correspond to means
of those adults caught during the week prior to the last egg sampling
date during a week. Note that soybean looper are plotted on a different
scale.



















A CABBAGE LOOPER


I.s 4
-I F s A< It




A' n i i i i
I A / ,













B SOYBEAN LOOPER









I 1 A 1 i













collards, and soybean looper in soybeans, in an 8-acre cropping system.








During the periods when no collards or catbage were present in the

cropping system (July 30-August 13, 1972 and July 22-August 19, 1973),

few if any cabbage looper eggs or larvae were found in the system. During

these periods, the only Plusiinae larvae present were collected from

bell peppers. Though not identified with certainty, they were probably

cabbage loopers.

Data on immatures (Fig. 4a) and adults (Fig. 3a) indicated there

were 7-8 generations of cabbage looper in 1972 and 5-6 generations from

January 1973-August 14, 1973. This is similar to what McKinney (1944)

thought occurred in Arizona.

Cabbage looper adult catches with blacklight (BL) traps baited with

cis-7-dda, and number of cabbage looper eggs in the field seemed to be

positively correlated in 1972 but not in 1973 (Fig. 3a). However,

increased rainfall in 1973 over that of 1972 may have influenced catches

and accurate identification of the Lepidoptera trapped.

Also, capture of adults of cabbage looper in cis-7-dda-baited BL

traps and virgin female-baited grid traps were very similar in 1972 but

in 1973 they differed greatly (Fig. 3a). After early May of 1973,

captures of cabbage loopers in grid traps were much lower than those of

the BL traps, and during several weeks "peak" captures in the BL trap

plot were "valleys" in the grid trap plot data (Fig. 3a). This may have

been the inverse relationship Hendricks et al. (1973) and Roach (1975)

reported for tobacco budworm and corn earworm.

The BL trap, grid trap, and egg count data (Fig. 3a) for cabbage

loopers did not suggest that cabbage looper activity was strongly in-

fluenced by lunar phases as was demonstrated for tobacco budworm by

Hartstack et al. (1973). However, lunar phase charts do not accurately









measure actual moonlight because of cloud cover and Lingren (personal

communication) has accumulated data which indicates cabbage looper activity

is strongly affected by moonlight intensity.

Hartstack et al. (1973) suggested that one parameter that might be

estimated from BL trap captures is the "mean rate of increase" such as is

illustrated in Fig. 5a. This view of the data is useful in illustrating

potential predictive patterns. In the period from April 14-May 24 both BL

trap capture data and eggs in the field were accumulating rapidly. Lower

"rates of increase" and rapid decline in numbers of eggs in the period

after September 26 are illustrative of the effect cool weather may have

on the population density of the cabbage looper in this region. Accumu-

lated BL trap captures of cabbage looper adults seemed to follow a similar

trend in 1972 as 1973.

Relatively few cabbage looper females were captured in BL traps.

Therefore data on mating was rather limited. However, the percentage of

mated females caught was highest in May (Table 4) when populations of the

cabbage looper were relatively low. Numbers of matings per female were

greater during this period when pheromone calling by native females was

probably most efficient. After May, percent mated females fluctuated

from 41.4 to 61.1 except during those months when <5 females were caught.

The major findings concerning seasonal abundances of the cabbage

looper was that it was very abundant in collards from May-September and

was at very low densities in the winter. Also adult trap data may be a

useful tool to employ in predicting seasonal occurrence and atun-lance

of cabbage looper populations.


Soybean looper

The soybean looper was not as abundant in the 8-acre cr:Lpirng system










A.PLUSIINAE


B. TOBACCO BUDWORM


I l
: VS1' ---


100~,f -- ^

%9 r



1. -- r


1 J1 i6 1I
J AN Ere


1A APR MAY JU L t SEP OCT 3O D E6
MARI APRI MAR JOR AL AUG SEP OCT NOV DIV


Fig. 5.--Rates of increase of cabbage looper, soybean looper, and
tobacco budworm indicated by cabbage looper pheromone-baited blacklight
trap captures of adults.


000C









Table 4.--Degree of mating of cabbage looper, soybean looper,
and tobacco bud.,dC.rm females trapped in cabbage looper pheromone-
baited light traps surrounding an 8-acre cropping system.


No. % mated Spermatophores/ Spermatophores/
Month dissected 0 o mated o
++ +

Cabbage looper

1972
April 1 0.0 0.0
May 10 90.0 1.1 1.2
June 10 60.0 1.7 2.8
July 15 46.7 1.0 2.0
August 87 41.4 0.8 1.8
September 12 41.6 0.5 1.2
October 4 0.0 0.0

1973
May 17 64.7 1.7 2.6
June 18 61.1 1.6 2.5
July 22 59.1 1.2 2.0
August 4 0.0 0.0

Soybean looper

1972
August 1 0.0 0.0
October 1 0.0 0.0

1973
July 1 100.0 2.0 2.0
August 2 100.0 3.0 3.0

Tobacco budworm

1972
March 10 100.0 2.3 2.3
April 60 95.0 4.5 4.8
May 17 76.5 1.1 1.5
June 25 88.0 1.9 2.2
July 265 81.9 1.6 1.9
August 22 86.4 2.2 2.5
September 43 69.8 1.4 2.0
October 5 20.0 0.2 1.0

1973
May 2 100.0 2.0 2.0
June 2 100.0 2.5 2.5
July 25 84.0 1.6 1.9
August 26 46.2 0.6 1.3








as the cabbage looper, but was found in 5 of the 21 crops (Table 2). It

was found most often in soybeans, however, tomatoes and peanuts also had

relatively high densities of soybean looper in 1972 (Table 5). Tomatoes

and peanuts were present in the system during much of the same period as

soybeans (Fig. 1).

Only 3 soybean loopers were collected from crops other than soybeans,

tomatoes, and peanuts in 1972 (Table 2). These occurred on collards early

and late in the season (spring and fall) when soybeans were either absent

from the system or not attractive as a host. All soybean loopers were

found on soybeans in 1973 except 1 (Table 2). This collection was made

in bell peppers during July, a period when soybean looper densities were

relatively high on soybeans (Fig. 4b). No soybean loopers were collected

and identified from the samples on wild hosts.

No immatures were found on plants within the 8-acre cropping system

until late May or early June (Fig. 4b). Counts of immatures indicate the

occurrence of only 3 generations in the system. However, densities were

so low on the crops, it is possible a generation may have occurred that

was not detected by the sampling techniques utilized.

In soybeans, densities of eggs and small (Fig. 4b) and medium larvae

were estimated at or below 1000 per acre on every sampling date in 1972.

In 1973 large larvae were estimated at densities of 1230 per acre during

the week of July 20 and small larvae were estimated at 1000/acre during

the week of Aujgst 5 (Fig. 4b).

Therefore the maximum densities of the soybean looper that occurred

in my study area were much lower than those reported by Burleigh (1972)

in soybeans growing in the "cotton agro-ecosystem" or by Teetes et al.

(1970) in sunflowers. Low densities in the 8-acre system, which contrast
















Table 5.--Relative number of larvae of soybean looper in soy-
beans, tomatoes, and peanuts in an 8-acre cropping system during
the summer of 1972.




Date Ca. no./acre (whole plant inspections and shakes)
(Week of) Soybean Tomatoa Peanuta


Jun. 25 0 80
Jul. 2 0 0 0
9 1,000 0 0
16 0 0 0
23 500 0 0
30 920 1,000 1,330
Aug. 6 170 500 0b
13 80 0
20 80 80
27 330 -
Sep. 3 330 -
10 580 -
17 330 -
24 0 -


a
Seven larvae from tomatoes, but
tified from these crops. However, no
from peanuts or tomatoes in 1972.

b


only 1 from peanuts were iden-
other Plusiinae were identified


Sweeps detected ca. 6.7 per 100 sweeps during this week.


_ ._








with economic infestations that can be induced with insecticide-treatment

of soybeans (Neal 1974), indicate that densities of the soybean looper

throughout its seasonal development may "normally" be low in the absence

of man's disruptive practices.

Although immature counts indicated 3 generations of soybean looper

occurred in 1972 in the 8-acre system, BL traps seemed to detect at least

4 generations during that year (Fig. 3b), similar to what Burleigh (1972)

found in Louisiana soybeans. Soybean loopers were first captured in cis-7-

dda-baited BL traps in early April (Fig. 3b). They were caught until late

October in 1972 and until sampling was terminated in mid-August in 1973.

In 1972 there was a peak in catch of soybean loopers averaging over 10

per BL trap/night during September and October which was very high relative

to numbers trapped earlier in the season. Most of these probably immi-

grated into the 8-acre system, and may have come from the nearby commercial

soybeans mentioned in Section I. Or perhaps they were migrating from the

norther part of their summer range (Mitchell et al. 1975).

Grid trap captures with cabbage looper-virgin female-bait were

generally much lower and more inconsistent than captures in cis-7-dda-

baited BL traps (Fig. 3b). This was perhaps because of substances) that

may be emitted by cabbage looper females, which inhibit soybean looper

attraction to female cabbage loopers (Mitchell 1972, 1973a).

Since adults of the soybean looper were caught prior to detection

of soybean looper eggs or larvae in the field in the spring, it appears

that BL traps may be helpful in warning of potential infestations of soy-

bean looper. Also, as with the cabbage looper, there is no clear evidence

from the data as developed and presented, of an effect of lunar phase on

soybean loopers (Fig. 3b).








The semilog plot of accumulated catch of soybean loopers indicates

"rates of increase" were quite constant during the period from May through

August, but increased drastically in late August and September in 1972

and to a lesser degree in June of 1973 (Fig. 4a). The rapid increase

may have been due to an influx of moths from commercial fields mentioned

previously or a migration similar to what Mitchell et al. (1975) suggested

might occur.

Only 5 soybean looper females collected from BL traps were checked

for mating (Table 4). The 2 collected in 1972 had not mated and all 3

collected in 1973 had. Mean number of spermatophores in those which

mated was 2.67.

The major differences between the seasonal occurrence and abundance

of soybean looper and cabbage looper indicated from our data are that the

soybean looper goes through fewer generations per year and it occurs at

much lower density levels than the cabbage looper in the absence of

applied control. It may have a lower intrinsic rate of increase as was

suggested by Endris (1973) but "rate of increase" during some periods of

my study (Fig. 5a) appeared to have been greater for the soybean looper

than the cabbage looper. However, immigration of soybean loopers into

my study area confound interpretation of the data. In contrast to

data for the cabbage looper, adults of the soybean looper were taken

in BL traps earlier in the spring than immatures were found in the field,

in both 1972 and 1973.


Tobacco budworm

Tobacco budworms were found in 10 crops of the 8-acre cropping

system, and in several wild hosts near the system (Table 6). They

occurred in substantial numbers in flue-cured tobacco, cigar-wrapper










Table 6.--Relative occurrence of species of Heliothis collected
in crops in an 8-acre cropping system.



% of each species on indicated crop
Number
Crop identifieda Tobacco budworm Corn earworm

1972
Flue-cured tobacco 433 99.8 0.2
Cigar-wrapper tobacco 166 98.8 1.2
Okra 178 79.2 20.8
White clover 42 64.3 35.7
Tomatoes 9 55.6 44.4
Peanuts 4 25.0 75.0
Grain sorghum 278 0.0 100.0
Sweet corn 253 0.0 100.0
Field corn 146 0.0 100.0
Millet 22 0.0 100.0
Soybeans 8 0.0 100.0
Cabbage 5 40.0 60.0
Bell peppers 2 0.0 100.0
Others 5 0.0 100.0

1973
Flue-cured tobacco 156 96.1 3.9
Collards 2 100.0 0.0
Okra 12 83.3 16.7
White clover 44 36.4 63.6
Soybeans 2 50.0 50.0
Tomatoes 4 25.0 75.0
Millet 5 20.0 80.0
Field corn 93 0.0 100.0
Sorghum 1 0.0 100.0



"Larvae" were identified in some stage after the 3rd-instar.

bThese larvae were identified in the adult stage to be corn
earworm.

CIncluding 1 each from collards, field peas, bush beans, pumpkins,
and squash.









tobacco, okra, and white clover, and infrequently (generally at densities

<300 per acre) in tomatoes, collards, cabbage, millet and soybeans (Table

6). They were also found at very low density levels in peanuts. This

contrasts with the studies of Snow and Brazzel (1953), in which no tobacco

budworms were found from samples in peanuts. The wild host plants on

which tobacco budworms were found included crimson clover, venus looking-

glass, small flower morningglory, beCgar-.'eed, and prickly sida. Of all

the wild hosts sampled, they were most numerous in crimson clever in the

spring of 1973 and prickly sida in the summer of 1972.

Since crimson clover was quite abundant in the Quincy area in 1973

during the period in which tobacco budworm were emerging from diapause,

it was probably a very important early season host of this noctuid this

agrees with results of Brazzel et al. (1953) and Snow and Brazzel (1965).

Tobacco budworms were also found on venus lookingglass in the spring, but

plants of this species were very scarce.

Immature tobacco budworms were present in crops of the 8-acre system

from early April to late October in 1972 and from early April in 1973

(Fig. 6). There were 6 major peaks in egg densities above 1000 per acre

in the system.in 1972 and 3 in 1973 (Fig. 3c).

Eggs of Heliothis spp. were first found from samples in or near the

8-acre system during April in flue-cured tobacco (Fig. 6b). Eggs were,

however, undoubtly present in white clover at or before the time they

were found in tobacco since large larvae were found in white clover

during late April and early May in 1972 and 1973, respectively (Fig. 6a).

Large larvae were also found on crimson clover at about this same time

during 1973, and eggs were probably present on this host at about the

time they were found in tobacco.









TOBACCO
, white clover
r


A1


BUDWORM


LfIA


Fig. 6.--Seasonal abundance of eggs and larvae of tobacco budworm
in flue-cured tobacco, okra, and white clover in an 8-acre cropping
system, estimates include some corn earworm.


u

0


---- ~~
- uui unr
--- uu unu


.1


AJA'
,A jffj








In white clover, which generally supported a portion of the tobacco

budworm population only in the spring (Fig. 6a), large larvae occurred at

a density of 680 per acre and 6.7/100 sweep during late April and early

May of 1972. No large larvae were detected in whole plant inspections

in 1973 and the maximum number found in sweeps in that year were down to

1.3/100 sweeps (Fig. 6a). An abundance of crimson clover during the

spring of 1l73 may have diluted densities of tobacco budworm in the white

clover of the 8-acre system.

All tobacco budworms but 1 identified from tomatoes were collected

in the spring, and the exception was collected on July 1, 1972. However,

densities of larvae in this crop were very low and made an insignificant

contribution to the population of the 8-acre system when compared to those

occurring in white clover, tobacco, and crimson clover in the spring.

In addition to crimson clover, venus lookingglass, white clover, tobacco,

and tomatoes, a few tobacco budworms were also found in the spring in

cabbage and collards in 1972 and 1973, respectively.

Tobacco in the 8-acre system was the major host of tobacco budworm;

ca. 99% of the larvae of Heliothis spp. collected from flue-cured and

cigar-wrapper tobacco were tobacco budworms (Table 6). And over 78% of

the tobacco bud:-.orms collected and identified in the 8-acre system came

from tobacco. Hence tobacco was the primary spring and summer host of

tobacco budworm (Fig. 1 and 6). In flue-cured tobacco highest numbers

of eggs occurred during the weeks of May 28 (29,830 per acre) and July 2

(37,170/acre) in 1972, and June 10 (43,670/acre) and July 8 (79,330/acre)

in 1973 (Fig. 6b). The 1st peaks of small larvae occurring in the spring

of 1972 and in 1973 were similar in size to egg peaks; however, subsequent

peaks of small larvae occurring in the summer were considerably lower














Table 7.--Relative number of immatures of tobacco budworm in
flue-cured and cigar-wrapper tobacco in an 8-acre cropping system
in 1973.



Ca. no./acre
Date Flue-cured tobacco Cigar-wrapper tobacco
(Week of) Eggs Larvae Eggs Larvae


Apr. 9 500 160 -
16 670 660 0 0
23 4,920 80 0 160
39 4,500 1,160 0 340
May 7 4,500 1,330 0 330
14 6,170 660 0 560
21 4,160 1,250 60 610
28 2,160 500 1,280 1,000
Jun. 4 2,160 1,080 1,940 940
11 6,160 330 3,560 1,660
18 12,500 0 60 3,610
25 4,830 80 1,660 2,000
Jul. 2 37,200 5,700 4,250 1,920
9 26,700 8,330 44,030 2,410
16 23,500 6,920 4,830 2,330
23 28,200 16,000 1,750 7,080
30 5,000 24,000 -
Aug. 6 170 6,170 -
-a
x 11,220 2,940 4,228 1,660



aData from April 9, July 30, and August 6 were not used for means.









than egg peaks. Estimates of large larvae per acre were considerably

lower than estimates for eggs, with highest estimates occurring during

the weeks of May 21 (1080), June 18 (2160) and August 6 (492,0) in 1972

and June 3 (3000) and June 17 (4170) in 1973 (Fig. 6b).

The cheese cloth cage was apparently quite effective in preventing

high levels of tobacco budworm infestations from occurring in cigar-

wrapper tobacco. Weekly egg and larval estimates indicate densities of

eggs in cigar-wrapper tobacco averaged 72% less than in flue-cured tobacco

and levels of larvae averaged 43% less (Table 7). However, in late June

the shade was ripped severely by winds and tobacco budworm eggs reached

densities of 44,030 per acre.

Toadflax and hop clover had been previously reported as important

early and mid-season hosts of the tobacco budworm (Barber 1937; Snow and

Brazzel 1965; Neunzig 1963, 1969). However, they were probably not im-

portant in the Quincy area, since I found no tobacco budworms on these

potential hosts after limited sampling of toadflax and extensive sampling

of hop clover.

A number of tobacco budworms were found on prickly sida growing

adjacent to the 8-acre system in the summer of 1972. However, densities

of larvae were much lower than those that occurred in flue-cured tobacco.

In addition to tobacco, prickly sida, and tomato, low densities of

tobacco budworm larvae were also found on okra, peanuts, millet, and

soybeans during early or mid-summer.

Similar to results of Snow and Brazzel (1965), but in contrast to

the results in the Quincy area of Chamberlin and Tehnet (1926b), I found

okra to be the major late season host in the 8-acre system. However, in

okra, estimates of numbers of eggs and larvae per acre were considerably








lower than had been found in flue-cured tobacco (Fig. 6c). Highest peaks

of eggs were estimated at over 1000 per acre during the weeks of August

20 (9500/acre), September 13 (3500/acre), and October 15 (6330/acre) in

1972 and August 12 in 1973 (4000/acre). Large larvae were never estimated

at over 700 per acre. Most of the larvae collected in okra in October

went into diapause.

In addition to okra, small flower morningglory (growing in or near

the 8-acre cropping system) and beggarweed (growing in the Quincy area)

were late season hosts of the tobacco budworm. Numerous eggs of Heliothis

spp. were found on flowers of the small flower morningglory in the late

summer and fall of 1972. Also, a substantial number of tobacco budworm

larvae were collected from one stand of beggarweed growing some distance

from the 8-acre system. Few plants of this host of tobacco budworm

occurred near the system, however. A few tobacco budworm larvae were

also collected in white clover in the fall of 1972.

Data on immatures (Fig. 6) and adults (Fig. 3c) indicated there

were 6-7 generations of tobacco budworm in 1972 and 4-5 generations from

January, through mid-August, 1973. Tobacco budworm adults were first

found in cis-7-dda-baited BL or virgin female-baited grid traps in the

spring on March 17 in 1972 and March 30 in 1973, and a few were captured

during the warm winter of 1971-72 in both BL traps and grid traps (Fig.

3c). BL trap captures of tobacco budworm adults seem to be positively

correlated with egg counts in tobacco and okra in 1972 but not in 1973

(Fig. 3c). This is similar to results for cabbage looper. Pheromone

trap catches did not seem to be as effective as BL trap catches as in-

dicators of the immature tobacco budworms in the field. The inverse

relationship of captures data from pheromone and BL traps observed by








Hendricks et al. (1973) and Roach (1975) was not as apparent from our

data; however, earliest captures of tobacco budworm in 1972, when the

adults occurred at low densities, were made with pheromone traps.

BL and pheromone trap capture data on tobacco budworms (Fig. 3c)

indicate tobacco budworm generation cycles may have been synchronized by

lunar phase as hypothesized by Nemec (1971) for the corn earworm. However,

egg counts did not reflect this trend.

The accumulated BL trap catches (Fig. 4) for tobacco budworm moths

seemed to follow a pattern similar to that plotted by Hartstack et al.

(1973). When "rates of increase" (from 1972) are calculated from points

similar to those chosen by Hartstack et al. (1973), the trend is similar

but reflects correspondingly higher population levels (2.29 and 8.33 as

compared to 1.40 and 5.75). My higher "rates of increase" may indicate

tobacco is a more favorable crop for tobacco budworms than cotton and/or

that there was less mortality of developing tobacco budworms in the Quincy

area. The higher catches per trap/night by Hartstack et al. (1973) in

Texas are probably due to the more effective trap used (40-w BL vs. 15-w

BL, see Hollingsworth and Hartstack 1972), less forested area in the Brazos

Valley, and.a greater abundance of suitable hosts in the vicinity of the

traps. Our semilog plot of accumulated catch of tobacco budworms in 1973

seems to follow a trend similar to that of 1972; however, catches were

lower (Fig. 4b).

Also similar to results of Hartstack et al. (1973), BL trap data

indicated the corn earworm began emerging from diapause earlier than the

tobacco budworm in the 8-acre cropping system (or Quincy area). This is

similar to field cage studies of rsring emergence of Heliothis spp. in

northeast Mississippi (Brazzel et al. 1953), but different from similar








field studies in North Carolina (Neunzig 1969).

A substantial number of females of the tobacco budworm were collected

in the BL traps near the 8-acre system (Table 4). Most were mated and

mean number of spermatophores per mated females was estimated from 1.0/?

in October to 4.8/? in April of 1972.

Results of measurements of the tobacco budworm population in the

8-acre cropping system were often comparable to those of the cabbage

looper. For instance the tobacco budworm was able to reach high densities

similar in magnitude to those of the cabbage looper. Also, the tobacco

budworm went through a similar number of generations. These characteristics

contrasted, however, with those of the soybean looper (Fig. 4 and 6).

Measurements of the population of tobacco budworms also differed

greatly in several ways from similar measurements of the population of

cabbage looper. Tobacco budworms were first detected in the spring by

BL traps (Fig. 5), much later than cabbage loopers; however, the BL traps

were baited with a synthesized pheromone of cabbage looper and soybean

looper. Still, tobacco budworms were detected somewhat earlier in the

spring than soybean loopers. Both tobacco budworms and soybean loopers

appeared to "emerge" more suddenly in the spring than cabbage loopers

(Fig. 5). Similar to a characteristic of the soybean looper detected

with BL traps, there was a period during the summer months in which the

tobacco budworm's "rate of increase" suddenly became greater. This

growth in the "rate of increase" occurred earlier for the tobacco budworm

than for the soybean looper, but also could have been due to immigration

from fields outside the study area.









Host Preference

Cabbage looper

More cabbage looper eggs and larvae were present on collards and

cabbage than other crops in all tests (Fig. 7a). In the 1-acre shade,

62 and 34% of larvae of the cabbage looper were found on collards and

cabbage, respectively (Fig. 7a). In the small cage test, the portion

of cabbage looper eggs found on collards (40%) and cabbage (30%) was

singificantly greater than those found on other available host plants.

Also, over 95% of the cabbage looper larvae found in the 8-acre cropping

system were on collards and cabbage (Table 2).

In addition to collards and cabbage, a few cabbage looper larvae

were found on bush beans, cigar-wrapper tobacco, and soybeans in the

1-acre shade (Fig. 7a), and on flue-cured tobacco, okra, soybeans,

tomatoes, and white clover in the 8-acre system (Table 2). Also, cabbage

looper eggs were found on all plants in the small cage with a sub-

stantial number on cocklebur.

These results indicate a strong preference of cabbage looper for

collards and cabbage with crops such as tomatoes, tobacco, soybeans, okra,

and white clover functioning as incidental hosts. Bell peppers and cigar-

wrapper tobacco were infested under caged conditions, but not in the

field. Therefore, it is likely that they are not normally a host of the

cabbage looper. However, crop rotation systems in which any of these

non-preferred hosts followed major plantings of collards or cabbage

could create damaging infestations of the cabbage looper in the non-

preferred hosts. Also, cocklebur should perhaps be controlled

and not used in rotation with cigar-wrapper tobacco (Kincaid 1960), since

substantial numbers of eggs were found on the plant in the small cage











CABBAGE LOOPER
A SHADE 18 )1/71





SX-X5-%T CAGEa -9/11)
o; !









A.


SOYBEAN LOOPER
,,A SHADE
054
036

o 'I







: 1



S 06 I
l234 56 8










B.
















S o.4
A 04
1 2 3 4 5 6 7












2 0 3., So bea
o 1 .Cllr


A (.8(11 pptrs
|. so 7.bemtoes
|- tSd.C tolebar

I 2 3 4 s S 7 O b.'":-i':;"SL




Fig. 7.-Mean number of eggs or larvae of cabbage looper, soybean


looper, and tobacco budworm per sample date in 7 crops compared in a
1-acre shade, a 6 x 4 x 5-ft cage, and an 8-acre cropping system.
Cockleburs were included in the small cage. Crops in the 8-acre system .
were seasonal with 14 additional hosts present during the sampling period;

means for each cropping system with the same letter are not significantly
different at the 1% level according to Duncan's new multiple range test.




56



test and since Lingren (personal communication) has previously observed

larvae of Plusiinae feeding on cocklebur in cigar-wrapper tobacco shades

in the area.


Soybean looper

Significantly greater numbers of larvae of the soybean looper were

found on soybeans than on other crops in the 1-acre shade (Fig. 7b). Also

greater numbers of larvae of soybean looper were found on soybeans than

on other crops in the 8-acre system (Table 2). However, relative to

crops other than soybeans in the system, high numbers of soybean looper

were found on tomatoes and peanuts in the 8-acre system (Table 5).

Relatively high numbers were also found on tomatoes and collards in the

1-acre shade (Fig. 7b). In addition, extremely light infestations of

soybean looper were found on collards and bell peppers in the 8-acre

system and on bush beans and cabbage in the 1-acre shade.

In the small cage test, significantly more eggs of the soybean

looper were found on cocklebur and tomato than on soybeans and the other

crops (Fig. 7b). This may have been due to differences in the condition

of the plants, but relatively high numbers of larvae were also found in

tomatoes in the 1-acre shade and in the 8-acre system. Therefore, plants

such as tomato, cocklebur, and peanut appear to be relatively attractive

as hosts for the soybean looper, but soybeans appeared to be the pre-

ferred host in my tests. At any rate, concentrated plantings of crops

such as soybeans, tomatoes, and peanuts could influence populations that

might occur on less attractive hosts such as tobacco, bell peppers, bush

beans, or collards. Also, concentrations of cocklebur could influence

the degree of infestation of the soybean looper in any of the host crops

and, therefore, should perhaps be controlled.








The soybean looper and cabbage looper were the predominant species of

Plusiinae found in the 8-acre system, however, a complex of Plusiinae

occurred within the system, including Argyrogamma verucca (F.), Autcyqraph"

biloba (Stephens), Rachiplusia ou (Guel.ee) and Trichoplusia oxygramma

(Geyer) (Table 2). A. verucca was found primarily on field peas, but a

few were found on soybeans, peanuts, bell peppers, and okra. A. biloba4

was found only on white clover and T. oxygramma occurred only on field

peas whereas R. o4 was found on white clover and collards. Since all of

the Plusiinae species appear similar in the larval stage, it is likely

that numerous mis-identifications have resulted from field identifications

of the complex.


Tobacco budworm

Tobacco, okra, and white clover were the hosts most utilized by tobacco

budworm in our tests. In the 1-acre Zhaue, larvsa were fund only on

cigar-wrapper tobacco, tomatoes,and bell peppers (Fig. 7c), but cigar-

wrapper tobacco appeared to be the preferred host. However, results

from the small cage test showed significantly greater numbers of eggs on

tomatoes (84%) than the other crops, although 11% of the eggs were de-

posited on tobacco. Bush beans, soybeans, bell peppers, and cocklebur

received the remaining 5% of eggs deposited in the small cage.

In the 8-acre cropping system, more larvae were found on flue-cured

tobacco than any of the other crops (Table 6), but substantial infesta-

tions were found on cigar-wrapper tobacco, okra, and white clover. Okra

became heavily infested only after tobacco was removed from the system.

Also, light infestations were found on cabbage, collards, tomatoes, and

peanuts.

4Both A. bilcba and R. ou (mostly R. ou) were found also on crimson
clover growing near the 8-acre system in 1973.








Fig. 7c presents the relationship of numbers of tobacco budworms

found on the 7 crops which were also tested in the 1-acre shade and small

cage. Cigar-wrapper tobacco was by far the most highly infested.

These results suggest that tobacco was the preferred host of the

tobacco budworm among the crops tested, but alternate hosts such as okra

and tomatoes were quite attractive during certain periods, especially

when tobacco was absent from the system. Also, white clover was an

attractive host and may function as an important alternate host in the

early spring and fall in the absence of more attractive plants, such as

tobacco and okra, and possibly tomatoes.

There were, of course, many variables in our tests such as prior

insect damage, physical conditions of plants, degree of destruction by

natural enemies, etc., that may have affected the intrinsic attractiveness

of the host plants to the tobacco budworm and the other 2 noctuids.

Radcliffe and Chapman (1966) stated that prior insect injury might have

affected preferences of the cabbage looper in their studies. In the 1-acre

shade both collards and cabbage were damaged extensively by the imported

cabbageworm, Pieris rapae (L.), with collards generally possessing the

highest numbers of this pest. However, despite this damage, these

crucifers were still "preferred" for oviposition by cabbage loopers in

my tests.

Pimentel (1961a) suggested differences in looper numbers in re-

sistance investigations might sometimes be the results of differences in

natural enemy destruction rather than differences in oviposition by the

species tested. In the 1-acre shade and 8-acre system, parasitism of

lepidopterous eggs was generally higher in tomatoes than in other crops.

However, like Plusiinae larvae, in all 3 of my test areas numbers of








Plusiinae eggs were very low in tomatoes especially when compared to

numbers in crucifers. Also, numbers of eggs of Heliothis spp. in the

8-acre system were very low in tomatoes relative to numbers in tobacco.

In the 1-acre shade the proportion of all eggs of Heliothis spp. collected

that were found in tomatoes was substantially lower than but still similar

to the proportion of total larvae collected that were found in this crop.

In their investigations on resistance within crucifers, Harrison and

Brubaker (1943) concluded that differences in numbers of loopers supported

by the various crucifers was due to variation in the general physical

condition of the crucifers. This certainly affected our results to some

degree. However, despite the effects of such variability and the small

number of reported hosts of these pests which were used in these investi-

gations, some trends were indicated.

Even though densities of tobacco budworm and cabbage looper were

quite high in all test areas, they selected a narrow range of hosts. Soybean

looper densities were much lower than the other test species, but the

soybean looper also selected a narrow host range.


Summary


Cabbage loopers increased rapidly in the spring to high densities

in collards and cabbage in the 8-acre cropping system. This pest was

found during most months of the year on collards and reached its highest

densities in May, June, and September. When collards and cabbage were

removed or appeared to be relatively unattractive, the cabbage looper

hardly utilized other hosts in the cropping system. Cabbage loopers

were not found on wild hosts. Catches in cabbage looper pheromone-baited

blacklight (BL) tr=ps were positively correlated with the number of







immatures in the field in 1972 but not in 1973. Collards and cabbage were

the preferred hosts of the cabbage looper in 3 different test areas al-

though several plant species served as incidental hosts.

Soybean loopers were found infrequently in the 8-acre cropping system

from June through October. They generally occurred in soybeans, but were

also found at relatively high density levels in tomatoes and peanuts. Cab-

bage looper pheromone-baited BL trap capture data were indicative of im-

matures of the pest in the 8-acre cropping system. Tests indicate soybeans

were preferred as a host over a number of other crops, although tomatoes,

cockleburs, and peanuts also appear to be attractive.

Tobacco budworm had rates of increase comparable to that of the

cabbage looper and increased primarily on tobacco in the 8-acre system.

However, a complex of hosts were important in the population dynamics of

tobacco budworn in the system. In the early spring, low densities of the

tobacco budworm were found on crimson clover, white clover, flue-cured

and cigar-wrapper tobacco, and a few larvae were collected from venus

lookingglass, tomatoes, cabbage, and collards. In the early and mid-

summer months, tobacco was the primary host although some were also found

from okra, prickly sida, peanuts, millet, and soybeans. The primary late-

season host was okra and it served as the host from which most tobacco

budworms in the 8-acre system went into diapause. Other late season

hosts included small flower morningglory, beggarweed, and white clover.

Tobacco budworms were active in the 8-acre system from early or mid-April

through October. Prediction of occurrence and densities of immatures by

utilizing data from BL traps and pheromone-baited grid traps appeared

promising. Host preference studies indicated tobacco was preferred by

the tobacco budworm over a number of crops but that okra, tomatoes, and

white clover are also attractive to this-species.
















SECTION III

PARASITOIDS AND PATH._GENS


In 1912, Pierce et al. recognized the important and integral role of

parasitoids and predators in the population dynamics of the boll weevil,

Anthonomus grandis Boheman. They presented a novel diagram of this

curculionid, its parasitoids and predators, and its interrelationships

with other species, including the cotton plant, other pests, and hyper-

parasitoids.

Allee et al. (1949) felt that this paper was particularly unique

in the field of synecology because of its constant emphasis on inter-

specific relationships. Since then, the importance of natural enemies

in suppressing many insect pests has been well documented (Hagen et al.

1971; MacPhee and MacLellan 1971; Rabb 1971).

After artificial suppression of their natural enemies, numerous

lepidopterous species can surge to pest status in many crops (Smith and

van den Bosch 1967; Reynolds 1971; Smith and Reynolds 1972; van den Bosch

and Messenger 1973). The cahbaqe looper (Falcon et al. 1968; Ehler et al.

1973), the soybean looper (Neal 1974), and the tobacco budworm (Ridgway

et al. 1967; Lingren et al. 1968a; Newsom 1972; van Steenwyk et al. 1975)

are, in many situations, examples of pests that have acquired importance

following elimination of natural enemies.

Parasitoids and pathogens are an important part of the natural enemy

complexes of many "lpidoFterous species (DeEach 1964, 1974; Huffaker 1971).

Egg parasitoids such as trichogrammatids destroy a large portion of many

61








populations of lepidopterous pests even before they begin feeding on their

hosts (van den Bosch and Hagen 1966). Some larval parasitoids destroy their

hosts in early instars and may prevent immediate damage to crops, but most

act through reduction in the breeding population of the next host generation

and may thereby prevent pest populations from increasing to injurious levels

(Elsey and Rabb 1970; Rabb 1971)

Most pathogens work in the latter manner by decimating lepidopterous

populations that have reached high densities. Generally, pathogens do not

effectively suppress population densities until the host population has

been stressed (e.g., by weather, another pathogen) (Burges and Hussey 1971).

DeBach (1974) stated: "Of those purposely imported, I know of no case

where a pathogen alone has produced outstanding biological control at low

levels but certain viruses have played a prominent role."

In the 8-acre cropping system there was -omething destroying many cab-

bage loopers, tobacco budworms, and soybean loopers between the egg stage

and large larval stage (Section II). In this portion of the study into the

population dynamics of the cabbage looper, soybean looper, and tobacco bud-

worm, I obtained information on the role of parasitoids and pathogens in

suppressing and regulating population numbers of these pests. Concerning

parasitoids I attempted to: 1) identify the major and minor parasitoids of

the cabbage looper, soybean looper, and tobacco budworm, 2) determine the

seasonal occurrence of these parasitoids, 3) investigate interrelationships

with their hosts and host-habitat, and 4) determine to some extent the

impact of the parasitoids on the populations of the 3 pests.

For pathogens I attempted 1) to determine what the major agents of

disease were. And 2) I attempted to measure seasonal occurrence of

disease in the populations of cabbage loopers, soybean loopers, and

tobacco budworms.









Literature Review


Cabbage Looper

Parasitoids

Ecological and biological studies designed to ascertain the signifi-

cance and importance of parasitism and parasitoid species in suppressing

and regulating the cabbage looper have been conducted in crucifers (Oatman

1966; Oatman and Platner 1969), some wild hosts of cabbage looper, alfalfa,

tree tobacco, Nicotiana glauca (Clancy 1969), lettuce (Oatman and Platner

1972), and cotton (Ehler et al. 1973) in southern California, crucifers

in New York (Sutherland 1966), and collards in North Carolina (Elsey and

Rabb 1970). At least 50 parasitoid species have been recovered from field-

collected cabbage loopers (Table 8). As many as 7 additional species may be

represented in collected material that has been questionably identified.

Three species complete development in eggs of cabbage looper and at least 45

utilize various larval instars. Two parasitoids are frequently recovered

from pupae of cabbage looper. Some (especially tachinids) nay be carried

over from host larvae to host pupae.

Parasitoids such as Trichogramma spp., some Apanteles spp., and Mete-

crus autographaeMuesebeck kill their host early in its life cycle, hence,

generally preventing major crop damage by an individual host. Others, such

as Voria spp., Eucelatoria armigera (Coquillett), and Lespesia archippivora

(Riley) may do little to prevent feeding by the host, but could help cause a

reduction in densities in subsequent generations of the host.

Several of the parasitoid species listed in Table 8 are not wide-

spread in distribution and appear to be incidental records. Other

generally attack other hosts, and may not be of major importance in the





64








Table 8.--Parasitoids of cabbage looper found in field studies in the United States.



Stage Parasitoid
attacked species References


Egg




Larval
and/or
pupal


Trichogramnatidae
Trichogramma evanscens Westwood
T. mn"ut-! e*e ,
T. pretiosam (Riley)

Braconidae
Aoanteles autographae Muesebeck.
A. congreeatus (Say)
A. glomeratus (L.)
A. 1i: .: -: Ashmead
A. natr ._i, -.,tr; i(Crezaon)
Acanteles sc
Cte..nu oL- :'.3jrni, Cameron
C. texanus Cresson
Meteorjs .t:r1:j-.9 Muesebeck
Mzcrol. E J i L- -- -s Ashmead
M. br a. : Muesebeck
M. cij"^-i- Muesebeck
Rogs cranulatus DeCant
R. molestus Cresson
R. perplexus Gahan
R. r-: o: :- al Gahan
Rogas sp.
Chalcididae
Brachnmeria ovata (Say)
Encyrtidae
Cooidosoma truncatellum (Dalman)
Eulophidae
Euclectrus ct~-St3:ii Howard
E, i-t :r.. :. ~t i.H Howard
Pe ". I-: .iirault)

Ic hTsu- ci-.c a- 2
Oc :, -- ,-u asqualis (Provancher)
Diadegma ,r .L e -.rersS3
Dia je-. sop.
-rrrzra ultrmus (Cresson)
Gel; cterallus (Say)
H, :T-rJ ex guae (Viereck)
I~era'i' stercorator orgyiae (Ashmead)
Ii:.----i5 conguisitor (Say)
Netelia sp.
Patrocloides mnotanus (Cresson)
Pteroco r-':. ies j3us (Cresson)
S_ -_:- -_,n ; -1 i:: cincticornis (Cresson)
_'.'uL_- cr .', ore s .-.ctor (Say)

Sarcodexia sterncdontis Townsend
Tachinidae
Archvtas californiae (Walker)
Co-sil' r :-:- (Meigen)
Euz-l.tori- a---Lzr3 rCoquillett)

Eus3svropa blanda bland (Osten Sacken)
Lespes La arc\,.- ?.':* *~ iy)
Les-esia sp.
MadreF.ya saundersii (Williston)
Perisoepsla hel.-us (Walker)
Phorocera so.
Phryie vulgaris (Fall6n)
Sihtona alusiae CoquLllett
Siphona sp. b
Voria ,'.rifronTs (?{wns.ndi
V. r.: Lati Tm'L-r:
i -'.-.. j-- ..- jstulata (F.)
W. rufooicta (Bigot)
Wint:- .A spp.


Note: Srach*-ecia intermedia (Neec) (Peck 1963) and Camooletis soncrensis (Cameron) (Lingren
at al. 1970; were recovered from cabbage loopers exposed to these parasi:oids in tne laboratory.

aParasitoid oviposition is in the host eggs.

According to C. W. Sabrosky, Systematic Entonolooy Laboratory, Beltsville, MD (personal
communication), V. aurifrcns probably is a synonym for V. curalis.


Oatman et al. (1968)
McKinney (1944)
Oatman (1966)


Muesebeck and Krcmbein (1951)
Riley (1833)
Chittanden (1902)
Muesebeck and Kromnbein (1951)
Boling and Pitru (1971)
Butler (1958a)
Fye and Jackson (1973)a
Ehler et al. (1973)t
Muesebeck and Krombein (1351)
Butler (1958a)
McKinney (1944)
Oatman and Platner (1969)
DeGant (1930)
Butler (1958a)
Butler (1958a)
McKinney (1944)
Wall and Berberet (1975)

Elsey and Rabb (1970)

Riley (1883)a

McKinney (1944)
Wall and Berberet (1975)
Oatman and Platner (1969)
Peck (1963)

Sutherland (1966)
Bayslip et al. (1953)
Sutherland (1966)
Sutherland (1966)
Sutherland (1966)
Oatnan (1966)
Sutherland (1966)
Muesebeck and Kronbein (1951)
Watson et al. (1966)
Clancy (1969)
Mitchell (1961)
Schaffner and Griswold (1934)
Muesebeck and Krombein (1951)

Aldrich (1927)

van den Bosch and Hagen (1966)
Schaffner and Griswold (1934)
Butler (1958b)
Watson et al. (1966)
West (1925)
Watson et al. (1966)
Clancy (19639)
Oatman (1966)
Clancy (1969)
Sutherland (1966)
Sutherland (1966)
Clancy (1966)
.Oatman (196i)
Wall and Berberet (1975)
Schaffner and Griswold (1934)
Allen (1925)
Schaffner and Griswold (1934)
Elsey and Rabb (1970)









population dynamics of the cabbage looper. Ten to 13 parasitoid species

are the largest numbers reported from several studies on their abundance

in populations of the cabbage looper (Oatman 1966; Sutherland 1966; Oatman

and Platner 1969; Clancy 1969); in most other publications, 5 or fewer

parasitoids are mentioned.

Trichogramma pretiosum, Copidosoma truncatellum (Dalman), and Voria

ruralis (Fallen) appear to be the major and most widespread parasitoids

of the cabbage looper; they are frequently mentioned in the literature as

being very important population suppression agents on many crops and in

numerous areas of the United States. Several other parasitoids are some-

times numerous in certain areas and may be important in suppressing popu-

lation densities of the cabbage looper. Foz instance, Hayslip et al. (1953)

reported that Diadegma insulare (Cresson) was important in reducing

numbers of cabbage looper on south Florida crucifers.

Sutherland's (1966) research indicated that Stenichneumon culpator

cincticoris (Cresson) and Vulqizhn;rmcn brevicinctor (Say) might be im-

portant regulators of cabbage looper on occasion in New York. In the

western U.S., Microplitis brassicae Muesebeck, E. armiqera, L. archippivora,

and Hyposoter exiguae (Viereck) are apparently important parasitoids of the

cabbage looper (Butler 1958ab; Oatman 1966; Clancy 1969, Oatman and

Platner 1969; and Ehler et al. 1973).

Some native parasitoid species may not be widespread in the U.S.,

nor often cause high mortalities in cabbage looper populations, but could

occasionally cause population numbers of cabbage looper to collapse because

they destroy the residue of a population already seriously depleted by

other mortality factors. In North Carolina Elsey and Rabb (1970) con-

cluded that Brachymera ovata (Say) might act as such a mortality factor










on the cabbage looper in some seasons.

Parasitism of cabbage looper eggs is very important in crop pro-

tection, since the cabbage looper is destroyed before it can feed.

Parasitism of cabbage looper eggs is almost exclusively by Trichogramma

spp. and T. pretiosum appears to be the species most commonly recovered

from cabbage looper eggs. McKinney (1944) found Trichogranma spp. had

parasitized up to 47% of the cabbage looper eggs he collected from lettuce

in Arizona one year, and Trichogramma spp. have frequently been recovered

from cabbage looper eggs in studies in California (Oatman 1966; Oatman

et al. 1968; Oatman and Platner 1969, 1972).

In crucifers, parasitism of cabbage looper eggs by Trichogramma spp.

was generally lower than 20% during studies by Oatman et al. (1968). But

in tomatoes, Trichogramma spp. were frequently observed to destroy at

least 40% of the cabbage looper eggs collected in studies by Graham (1970)

and Oatman and Platner (1971). In many crops, estimates of parasitism of

cabbage looper larvae has often been higher than those for egg parasitism,

probably because of longer exposure of the larvae to a variety of

parasitoid species. McKinney (1944) stated that "larval parasites seem

to be more uniformly distributed from field to field than do the egg

parasites and exercise a more effective control against the looper."

Oatman (1966) collected 1,737 cabbage looper larvae from California

crucifers; 26% of the larvae were parasitized, mostly by tachinids. On

2 dates, over 90% of the larvae collected were parasitized. V. ruralis

and C. truncatellum were the primary parasitoids recovered, but 7 others

were also considered to be of importance.

Oatman and Platner (1969) 3ater found additional evidence that larval

parasitism was an important mortality factor of cabbage looper on cabbage









in southern California, but mortality was often low during the summer

months. V. ruralis, the dominant parasitoid of 12 species recovered, was

most frequently found in the fall and winter. H. exiguae and C. truncatellum

occurred most commonly during the summer and fall.

Clancy (1969) found similar trends of parasitism from collections of

larvae from wild hosts, alfalfa, and tree tobacco in California with the

total larval parasitism being highest (41%) in tree tobacco. Larval

parasitism was greater (over all crops and wild hosts) from August-January

than during other periods of the year. McKinney (1944), Butler (1958b),

and Brubaker (1968) found V. ruralis was the most common parasitoid of

cabbage looper larvae collected from weeds and cultivated crops in Arizona,

and that it was most abundant during late fall and winter.


Pathogens

Relative to those conducted on parasitoids, few seasonal field sur-

veys have been conducted to quantitatively determine the importance of

pathogens in suppressing and regulating population numbers of the cabbage

looper (or the soybean looper and tobacco budworm). Hofmaster (1961) did,

however, monitor the incidence of nuclear polyhedrosis virus (NPV) on

cabbage near Pointer, VA, and Semel (1956) and Sutherland (1966) reported

on NPV occurring in cabbage looper populations in New York.

From collections of Plusiinae, probably primarily cabbage looper, in-

cotton fields in Alabama, Harper and Carner (1973) did not find much

incidence of disease until early August. Eight percent of the Plusiinae

larvae collected were diseased with Entomophthora sp., 2% with Namuraea

(= picaria of authors)sp., and 41% with NPV.

NPV has been considered to be a very important mortality agent for

many years (Chapman and Glaser 1915). It is the most obvious pathogen








of loopers which reach high densities in crops such as crucifers and

cotton (Creighton 1973).

Other pathogens that have been found in and isolated from cahbage

loopers are Nosema trichoplusiae (Tanabe and Tamashiro 1967), cytoplasmic

polyhedrosis viruses, granulosis viruses, Spicaria prasina (Burges and

Hussey 1971), Bacillus thuringiensis (Cameron 1971), Nomuraea rileyi,

Entomophthora megasperraa, Ee~u.aria bassiana, .A r ilug flavus,

Penicillium sp. (Thcas and Poinar 1973), Entnr.prthora sphaerosperma

(Yendol and Paschke 1967), and Metarrhizium anisopliae (Creighton 1973).


Soybean Looper

Parasitoids

Much less is known about the soybean looper than the cabbage looper

since it is not as economically serious a pest (Section II). However,

Burleigh (1971, 1972) did study the parasitoid czcplex which affected the

soybean looper in 3 cropping systems in Louisiana. He found parasitism

by parasitoids can be an important regulatory factor in the population

dynamics of the soybean looper.

Prior to Burleigh's studies, Janes and Greene (1970) found 9% of the

soybean looper larvae they collected from sweet corn ears were parasitized

by C. truncatellum. Another 8% were destroyed by a small unidentified

Hymenoptera.

Burleigh (1971) found 7 parasitoids from soybean looper larvae: C.

truncatellum, M. autographae, Apanteles scitulus Riley, Lespesia aletiae

(Riley), B. ovata, Rogas molestus Cresson, and Mesochorus sp. (a hyper-

parasitoid). C. truncatellum, the most common parasitoid, occurred

throughout the sampling period, but was most abundant from mid-July to

late August. L. aletiae was also a significant mortality factor (Burleigh

1972).








A. scitulus was also abundant, particularly in June and July, and in

1 area was the major parasitoid (Burleigh 1971). During 1 year, many

A. scitulus were parasitized by Mesochorus sp.

Percent parasitism of total collected larvae ranged from 3.7 46.3%

(Burleigh 1971). Generally parasitism declined in each successive genera-

tion of the soybean looper occurring during a year, particularly when

incidence of a fungal pathogen, Nomuraea rileyi increased. Parasitism

was lower in a "cotton and soybean ecosystem" (where soybean looper

density was the highest) than in a "rice ecosystem" and in

a "cleared hardwood forest ecosystem" (Burleigh 1972). Parasitism by

parasitoids was the major mortality factor in the 1st generation of the

soybean looper, but it was less noticeable in subsequent generations.


Pathogens

Harper and Carner (1973) felt a rapid decline in soybean looper

population densities in late August in Alabama soybeans was principally

due to pathogens since the major parasitoid, C. truncatellum, parasitized

few larvae (<1%) and few predators were observed. They found peaks

in incidence of disease in soybean looper populations occurred in early

August and September. In contrast to the cabbage looper in cotton, none

were diseased with NPV, but a few were diseased with Nomuraea sp., and

35% of the soybean looper larvae collected in 1 field survey were diseased

with Entomophthora sp.

Like Burleigh (1971), Gudauskas and Canerday (1966) determined N.

rileyi to be a pathogen of soybean looper. Also, from diseased soybean

looper larvae collected from cotton, peanuts, and soybeans in Alabama,

Watson et al. (1966) isolated N. rileyi and a bacterium, Streotococcus

sp. from soybean loopers.










Tobacco Budworm

Parasitoids

The importance of parasitoids in regulating tobacco budworm popula-

tion numbers has been recognized by numerous authors (Chamberlin and

Tehnet 1926a; Morgan and Chamberlin 1927; Wene 1943; Grayson 1944; Wille

1951; Noble and Graham 1966; van den Bosch and Hagen 1966; Lewis and

Brazzel 1966b; Lewis and Brazzel 1968; Rabb 1971; Ridgway and Lingren

1972). Some of the major parasitoids which have been recovered from

tobacco budworm are presented in Table 9. Most work on parasitoids of

the tobacco budworm occurred in tobacco and cotton, the primary hosts of

the tobacco budworm, but several studies have also been conducted on wild

host plants.

The several papers published on Cardiochiles nigriceps Viereck have

yielded considerable information on the seasonal occurrence of this

parasitoid. Chamberlin and Tehnet (1926a) usually detected C. nigriceps

at Quincy in the spring soon after the tobacco was planted. This braconid

was numerous from May until September. In July and August, 3-4 adults of

C. nigriceps were frequently seen flying around a single stalk of tobacco

by Chamberlin and Tehnet (1926a). In cage tests, C. nigriceps emerged

from overwintering diapause during a period of March 20 September 11

and adults were found as late as November 3.

C. nigriceps occurred in Virginia tobacco from late June to late

August (Grayson 1944). Snow and Burton (1967) found C. nigriceps in

beggarweed in Georgia from August 11 September 1. It was reared from

larvae collected from Abutilon trisulcatum in the Rio Grande Valley during

October 27 November 2 when 56.3% of the larvae collected were parasitized,

and November 4-10 when 13.3% of the larvae were parasitized (Griham et al.





71









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1972). Neunzig (1969) found larvae parasitized by C. nigriceps in tobacco,

cotton, and deergrass from May 26 October 10.

Another parasitoid of the tobacco budworm about which there is

limited information on seasonal abundance, is Campoletis sonorensis

(Cameron). In North Carolina parasitism by this icheumonid was reported

to be >70% from late May until late July in tobacco (Rabb 1971). From

early July to mid-October substantial parasitism by C. nigriceps occurred

and parasitism by C. sonorensis was generally low. In late October and

early November, C. sonorensis was the only parasitoid found.

Egg parasitoids of tobacco budworm are important in crops such as

tomatoes (Graham 1970) and cotton 'Lingren 1969). Graham (1970) found a

large percentage of tobacco budworm eggs on tomatoes were attacked by

Trichogramma semifumatum Perkins, but rarely has egg parasitism been

observed on tobacco (Rabb and Bradley 1968; Gentry et al. 1973). Rabb

and Bradley (1968) suggested that eggs on tobacco are not parasitized

because of the sticky surface of a typical tobacco leaf.

Larval parasitoids are much more effective on tobacco than are egg

parasitoids. In southeastern U.S. tobacco, Cardiochiles nigriceps has gen-

erally been the most common parasitoid. Chamberlin and Tehnet (1926a) often

found that during July and August, 50-100% of tobacco budworms collected

in tobacco were parasitized. Grayson (1944) estimated 15-43% parasitism

by C. nigriceps in various lots of tobacco budworm collected in Virginia

tobacco.

Parasitism by C. nigriceps in Snow and Burton's (1967) field of

beggarweeds ranged from 0-34%. Neunzig (1963) found that 50% of the

tobacco budworm larvae collected on deergrass in August of 1958 were

parasitized by C. ni~_-iz-s, but only 5% were parasitized in 1961.









Later Neunzig (1969) reported parasitism by C. nigriceps of tobacco

budworms collected on various dates in various fields of tobacco ranged

from 11.5 94.0%. In cotton parasitism of tobacco budworms by C. nigrceps

ranged from 0-100%. No C. nigriceps were recovered from tobacco budworms

collected in toadflax during the period of April June and few were

found from those collected in deergrass from July September.

Campoletis sonorensis is also commonly mentioned in the literature as

an important parasitcid of tobacco budworm. Wene (1943) found that C.

sonorensis parasitized from 14 94% of the tobacco budworms collected

in tobacco fields and plant beds in Virginia. Tobacco budworm larvae

in the sampled fields were rarely larger than 3rd-instar. Grayson (1944)

estimated parasitism at 15 43% by this species in Virginia tobacco.

In their studies on wild host plants of Heliothis spp., Graham et al.

(1972) found Cam-ol3tis sp. (which accounted for 76% of the parasitoids

identified) and Micropletis croceipes (Cresson) to be the most common

parasitoids of tobacco budworms on wild tobacco and Ruellia runyonii.

Parasitization of tobacco budworms on wild tobacco was 20 41% from

March 10 May 21. On R. runyonii it was 0-59% from April 28 August 31.

Watson et al. (1966) found parasitism of tobacco budworms to be higher on

beggarweed than on other hosts, but "the parasite involved was the

ichneumonid, Netelia sp. .

Numerous other studies of Heliothis spp. on cotton and other crops

contains an abundance of information on parasitoids of the tobacco budworm

(Ridgway and Lingren 1972). Apanteles marginiventris (Cresson) and

Microplitis croceires appear to be 2 other species that are particularly

important suppressants of tobacco budworm densities.









Pathogens

In their studies of pathogens and other natural enemies of the tobacco

budworm, Watson et al. (1966) isolated Aspergillus flavus, Penicillium sp. ,

Rhizopus sp., _c-nuraea Spicaria of authors) sp., other bateria, and

a suspected virus from diseased tobacco budworms. Nosema heliothidis

has also been isolated from tobacco budworms (Burges and Hussey 1971).

Like the cabbage looper, Heliothis spp. also suffer from infections

caused by NPV but the NPV of Heliothis spp. "is not so highly virulent

as that of the cabbage looper" (Dulmage 1972).


Methods and Materials


Collections of eggs and larvae of cabbage looter, soybean looper,

and tobacco budworm, and other Plusiinae, corn earworm, and several other

Lepidoptera, were made in the 8-acre crccping system, and adjacent or

nearby wild hosts, as was reported in Section I. These were taken in

order to monitor parasitism and incidence of disease acting on the

populations of cabbage looper, soybean looper, and tobacco budworm dis-

cussed in Section II. Collected eggs and larvae were checked at 3-4 day

intervals for parasitoids, and for disease (Burges and Hussey 1971).

Egg parasitism was determined under a stereo-dissecting scope by

noting the presence of the blackened appearance of the shell produced.

by Trichogranma spp.' or finding adult parasitoids in the containment

area. Larval parasitism was determined by emergence of parasitoid adults

or presence of parasitoid larvae in the lepidopterous larvae after death

of the host larva was observed. Records of parasitism and other records

were kept on the "egg cards" or larval cup tops until all information

desired was obtained. These larvae which appeared to die of starvation









were not used in calculating parasitization or disease.

I removed egg and larval parasitoids from the cups and cards as they

developed to the adult stage and either "pinned" them or placed them in

small glass vials of ca. 70% ethanol. In 1973 I removed parasitized

(blackened) eggs from the tape-made-cells and placed them in small clear

gelatin capsules (size 000) in order to prevent parasitoids emerging from

eggs from becoming entangled in the sticky tape. After collections were

made most larval parasitoids were sent to E. E. Grissell, Div. Plant

Industry, Gainesville, FL and most egg parasitoids were eventually sent

to S. Nagarkatti, CIBC, Bangalore, India for identification.

Lepidoptera collected in the 8-acre system, in addition to Plusiinae

and Heliothis spp., included velvetbean caterpillar, Anticarsia gemmatalis

Hubner, green cloverworm, imported cabbageworm, fall armyworm, Spodoptera

frugiperda (Smith), tobacco horn'.orm, M'anduca se::ta (L.), diamondback moth,

Plutella xylostella (L.), Anomus sp., Prodenia sp., and Agrotis sp.

Velvetbean caterpillars were collected from a number of crops, but eggs

were especially numerous in 1972 in field peas, during August and

September, and in white clover, during September, October, and November,

and relatively large samples were taken. Relatively large samples of

larvae of green cloverworm were taken in 1973 in white clover, during

February and early March, when they were numerous in this crop. Fall

armyworms were most numerous in May and early June of 1973 in field corn,

and relatively large collections of this pert was made. High

numbers of imported calbageworm eggs were collected during several periods

during the spring, summer, and fall in collards.

In addition to collections of wild material, laboratory-reared

cabbage looper eggs were introduced into the 8-acre cropping system on









several dates during the summer- of 1972 by placing the eggs individually

on plants of the system with egg albumin as a sticker (Whitcomb and Bell

1964), or by pinning masses of eggs that were oviposited on paper towels

to plants in the cropping system. These were collected after 24-48 hr in

the system, but recovery of eggs was very low, presumably because of

predation.

Additional monitoring for the presence of Trichogramma spp. and

other egg parasitoids were undertaken in 1973 in the 8-acre cropping

system. Two to 4 potted tomato plants bearing eggs of laboratory-reared

tobacco budworms were placed within various crops of the 8-acre system on

several dates in March, April, and :May, and collected 24-48 hr later.

Tobacco plants possessing tobacco budworm eggs were also placed in crops

of the 8-acre cropping system to further substantiate that parasitoids

avoided ovipositing in host eggs laid on this plant.

Collections of eggs and larvae of Plusiinae and Heliothis spp. were

also made in the 1-acre shade (Section I) in order to monitor parasitism

and disease. Some of these data were used for development of this section.

Methods were similar to those for the 8-acre system.

Although the only index provided from my studies of abundance of

most of the parasitoids, was the rate of parasitism of the immature

Lepidoptera collected, abundance of Cardiochiles nigriceps adults was

measured on one date (July 7, 1972) by 3 methods. First, the presence or

absence of C. nigriceps adults on or near 50 tobacco plants were recorded,

Second, the number of C. nigriceps adults per plant on 20 randomly selected

plants was recorded. Third, the number of C. nigriceps that visited a

plant during one minute was recorded for 5 plants.









Results and Discussion


Earasitoids

Parasitoids recovered from Lepidoptera collected in the 8-acre

cropping system are presented in Table 10. At least 11 parasitoids were

collected from cabbage loopers, and 7 were relatively common.

Six different parasitoid species were collected from soybean loopers

with each being about equally common. Four were species reared from the

cabbage looper; however, the tachinids, Lespesia aletiae and Chaetophlepsis

townsendi (Smith) were not recovered from Plusiinae thought to be cabbage

loopers.

At least 6 parasitoids were collected from the tobacco budworms;

however, Cardiochiles nigriceps was by far the predominant parasitoid.

C. nigriceps, Campoletis sonorensis, Telenomus heliothidis Ashmead, and

Netelia sp. were collected only. from Heliothis spp. which may have all

been tobacco budworms. I did not note Trichogramma fasciatum (Perkins)

or Telenomus heliothidis Ashmead recovered from tobacco budworm, Tricho-

gramma fasciatum (Perkins) or Trichograrnma perkinsi (Girault) recovered

from cabbage loopers, or Chaetophlepsis townsendi, Apanteles marginiventris,

or Trichogramnm pretiosum recovered from soybean loopers, in the literature

I reviewed.

Although Copidosoma truncate.lum, Voria ruralis, and Cardiochiles

nigriceps were relatively stenophagous parasitoids, many of the parasitoids

of Plusiinae and Heliothis spp. were oligophagous. For instance, T.

pretiosum was discovered from eggs of Heliothis spp., Plusiinae, and

at least. other lepidopterous species. A. marginiventris and M.

autographae were found from Heliothis spp., Plusiinae, and several other

lepidopterous species. T. perkinsi, Eucelatoria rubentis (Coquillett),





78










Table 10.--Parasitois reared from lmm.ature cabbage loopers, soybean loopers, tobacco budworms.
and other Lepidoptera collected from an 8-acre cropping system and in nearby wild hosts.



ex Plusiinae ex Heliothis




a



Host stages ,' -
necessary for a ex
development i'arasitoid species S Mi others


Trichoarammatidae
Trichocramm'a spp.
T~ L etiosm (Riley)
T. 3- -e: Ir ns







Sc r, L_ .L .
Telero~'.s heliothidis Ashmead
Telerineus sp.
T. schiigis Ashmead

Braconidie
M.teorus auto rt IMusebeck
An r-ele mar n ventris Creason
oP s r .
Ichneuro' idae
Cairoletis senorer.ns (Cameron)
C. flaviclnatta ti3i ad)



Encyrtidae
Cz,-d =,mi truncatellum (Dalman)
3)'*, .u~-
Cnelonus texanus Cresson

Braconidae
C73rsochi.- rigrriceps Viereck
A. .:or 2pr, Huesebeck
A. oleoratuss (L.)

ru l r L .)
E iectrus plathyoenne Howard
Euclectrus sp.
Ichneuro'nidae
i. i! pacificus melleus

Hetelia sp.
.'r,:. ancyloneura (Cameron)
(',tr*cn sp.
Tachitndae
Varia ruralis (Fallin)
Euel- t~ .:-- (Coquillett)
i: a. _I r. iley)

;Ahe ,'- cl-. co.rsendi (Smith)

Archytas marmoracus (Townsend)


X ++
++
++

++


++ +* + ++ x ++
++ ++ + + X ++


x
x x


++ ++ ++ x


++ ++


+4 4-


++ ++
+ +
x x
+
4+
x


++ x
+4


+ 4 +
x x
x
x
x
+ + x


Early stages
Egg


Larval


Early and
later stages
Ecq-larval




Larval or
larval-pupal

















Table 10.-Continued


ex Plusiinae ex Reliothis








Host stages a
necessary for e
development Parasitoid species S others


Unknowng Braconidae
Zeie s.
Ichneunonidae
S.x

PC r if j.: Cresson) X
Pc ro0a' i_- 3
sp. of Pteromalidae
Eupterosaluh sp.


Note: Based on data from Plusiinae and Reliothis spp. the symbols are used as follows: ++,
commonly found in some seasons and crops; +, occasional; -, care; =, very rare: x, not enough data
to establish if rare, etc. None found frora Trichoplusia oxygrarna.

aVelvetbean caterpillar, green cloverworm, ijrported cabbageworm, fall armyworm., tobacco horn-
worm, diamondback moth, Anoius sp., Prodenia sp., cr Agrotis sp.
bDetermined by L. R. Ertle, Aqr. Res. Serv., USDA, Newark, DE, and Sudba Nagarkatti, CIBC,
Banglore, India.
CDetermined by Sudha :a=irkitt i, according to L. R. Ertle (letter dated 5 December 1972) "her"
T. semifunatum is similar L: 1' T. pretiosum.
dA new species according to L. R. Ertle (letter dated 5 December 1972).
possible new species described by L. R. Ertle (t. nubilalum Ertle) according to Sudha Nagar-
katti (letter dated 20 January 1973).
fFrom 1 Plusiinae egg collected in the I-acre shade.
gor difficult to fit into upper categories.









Lespesia archippivora, Chaetophlepsis townsendi and Archytas marmoratus

(Townsend) were all found from at least 2 different hosts.

Seasonal occurrence

Those parasitoids which were oligophagous (i.e. various Trichogramma

spp., Meteorus autographae, and Apanteles marginiventris) were frequently

collected, and were collected during most seasons of the year (Fig. 8). The

records for M. autographae in January, February, and most in March, and for

A. marginiventris in February, and most in March, were from green cloverworms

collected in white clover. Most other records for these parasitoids were

from Plusiinae or Heliothis spp. in various crops.

Trichogramma spp. were abundant in the 8-acre system from April to No-

vember (Fig. 8). The 1st eggs parasitized by Trichogramma spp. were not

collected during each spring until April 7, 1972 or March 14, 1973 even

though a number of potential host eggs were collected prior to these dates.

Early records were from Plusiinae eggs in collards and Heliothis spp. eggs

in tomatoes. In the fall parasitized eggs were collected as late as Novem-

ber from velvetbean caterpillar eggs in white clover. They were also found

as late as October in Plusiinae eggs in collards, in velvetbean caterpillar

eggs in field peas, and in Heliothis spp. eggs in tomatoes and squash.

Copidosoma truncatellum and V. ruralis were not oligophagous. But both

were collected during all seasons of the year though the number of V. ruralis

was relatively small. It may have been difficult for the latter species to

increase because of the prevalence of nuclear polyhedrosis virus (NPV) with-

in the cabbage looper population from about June through September. The

polyembryonic C. truncatellum was perhaps more successful in competing with

NPV. However, since C. truncatellum was recovered from all sizes of
































































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