Tomato pinworm, Keiferia lycopersicella (Walsingham)


Material Information

Tomato pinworm, Keiferia lycopersicella (Walsingham) population dynamics and assessment of plant injury in southern Florida
Keiferia lycopersicella
Physical Description:
xvii, 265 leaves : ill. ; 28 cm.
Peña, Jorge E., 1948-
Publication Date:


Subjects / Keywords:
Tomato pinworm   ( lcsh )
Tomatoes -- Diseases and pests -- Florida   ( lcsh )
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )


Thesis (Ph. D.)--University of Florida, 1983.
Includes bibliographical references (leaves 230-242).
Statement of Responsibility:
by Jorge E. Peña.
General Note:
General Note:

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 000372978
notis - ACB2148
oclc - 10033340
System ID:

Full Text








I thank Dr. Van Waddill, my advisor and chairman, for his

encouragement, support and friendship, but most of all for his valuable

suggestions and allowing me freedom to conduct my research.

I would also like to express my appreciation to the following


Dr. S.H. Kerr for his interest in teaching me the art of

communication and also for his help in solving administrative problems

during my studies.

Dr. J.L. Stimac for his help and constructive criticism, as

well as his ideas to improve the quality of this study.

Dr. K.H. Pohronezny for his constructive criticism, suggestions

and for reviewing this manuscript.

Dr. D.J. Schuster for supplying material for my research as

well as his interest in this study.

The Agricultural Research and Education Center, Homestead,

Florida, and to Dade Agricultural Council for providing the grantmanship

and scholarship to support my studies.

The staff of AREC, Homestead, for their cooperation, espe-

cially Jonnie Csterholdt, Carolyn Reitman, Susan Housley, Leslie

Sawyerlong, Rodney Chambers, Linda Douthit, and Wilbur Dankers for

their help during data collection. Mrs. Sheila Eldridge and Mrs.

Barbara Hollien for kindly typing this manuscript.

Drs. R.E. Litz and S.K. O'Hair for their friendship, encourage-

ment and support during the past years.

Mr. Ben Gregory for his honest friendship and willingness to

share ideas in research.

Ms. Annie Yao, Mr. A. Bustillo, Mr. W. Chongrattanameteekul,

Mr. K. Patel and Mr. C. Ho for their friendship and support.

I am indebted to my family for their love and encouragement,

the Litz family, Eleanor Merritt and Bunny Hendrix for their friend-

ship and support.






ABSTRACT . . . .


. ii

. vi

. xi
.... xv




Family Gelechiidae . .
Studies on Keiferia lycopersicella .
Tomato Plant Phenology and Measurement of TPW
Dispersion and Economic Damage .
Environmental Factors Affecting TPW Population

. 6
. 7

. 19
. 21


Introduction . . .
Materials and Methods . .
Results and Discussion . .
Conclusions and General Discussion . .


Introduction . . .
Materials and Methods . .
Results and Discussion . .
Conclusions and General Discussion . .


TN TOMATOES . ... 89

Introduction . ... . 89
Materials and Methods. . .. .90
Results and Discussion . .. .91
Conclusions and General Discussion . .. .117







Introduction . . .
Materials and Methods . .
Results and Discussion . .
Conclusions and General Discussion .


Introduction . . .
Materials and Methods. . .
Results and Discussion . .
Conclusions and General Discussion .

. 119

. 154


Introduction . . .
Materials and Methods. . .
Results and Discussion . .
Conclusions and General Discussion .


Introduction . . .
Materials and Methods. . .
Results and Discussion . .
Conclusions and General Discussion .


Introduction . ... ...
Material and Methods . .
Results and Discussion . .




. 213





. 230




Table Page

1 Larval parasites of Keiferia lycopersicella
reported from U.S.A. and South America until 17
1981 . . .

2 Classification of tomato pinworm leaf
damage on 'Flora-Dade' tomatoes, based on
greenhouse and field observations. Homestead,
Florida, 1980 . . .

3 Leaf area and reproductive plant structures in
tomatoes, cv Flora-Dade', planted on 5 dates
in Homestead, Dade County, Florida during 1980-
1981 . . .

4 Stage of development description for tomato cv
Flora-Dade. Description is based on the average
of observations from tomato plants grown during
Fall 1980 through Winter 1981. Homestead,
Florida . . .

5 Tomato leaf weight and leaf area consumed by
different larval instars of Keiferia lycopersicella
under greenhouse conditions; T 24+3C, 75+2% RH.

6 Percentage of tomato pinworm larval occurrence in
foliar injuries with different phenological charac-
teristics . . .

7 Comparison of different sample sizes for tomato
pinworm eggs. Homestead, Dade County, Florida,
1980 . . .

8 Mean number of tomato pinworm eggs per plant by
planting date for 8 tomato plantings in Homestead,
Florida, 1979-1981 . .

9 Ovipositional preference of tomato pinworm for
upper and lower surfaces of tomato leaves from
plants grown under greenhouse and field
conditions . .... .. *

Table Page

10 Mean number of tomato pinworm eggs in 2 plant
strata (upper and lower halves) per plant at
different sampling dates. Homestead, Dade
County, Florida, 1980 . 65

11 Mean number of tomato pinworm eggs per plant in
6 strata: upper, middle and lower external; upper,
middle and lower internal canopy of the tomato
plant. Homestead, Florida, 1981 . 67

12 Relationship between daily mean temperature ( C)
and TPW oviposition in 6 tomato plant strata.
Homestead, Florida, 1981 . .. 71

13 Percentage distribution of TPW eggs for each stratum
of tomato plants in 5 tomat plantings. Homestead,
Dade County, Florida, 1980 ...... 75

14 TPW egg sample allocation for 6 plant strata during
3 different plant stages: second vegetative (TR ),
first reproductive (TR1), and second reproductive
stage (TR2) . . .... 77

15 Mean tomato pinworm eggs on tomato leaves from
different strata of 45 day-old plants. Homestead,
Florida, 1980. . ... 79

16 TPW egg sample allocation on tomato leaves numbered
from bottom to top. Plants 45 days old. ... 81

17 Relationship between frequency of occurrence of TPW
eggs per leaflet as dependent variable and distance
among eggs and leaflet area as independent vari-
ables . ............. 82

18 TPW oviposition on tomato at different plant stages.
Homestead, Florida, 1981 . .. 86

19 Sample size and relative net precision (RNP) for
sampling injuries at low and high population
densities. Homestead, Dade County, Florida, 1980. 93

20 Mean number of TPW foliar injuries and standard
error on different sampling units at specified
date. Crop planted in Nov., 1979. Homestead,
Florida . . 96


Table Page

21 Mean number of TPW foliar injuries and standard
error on different sampling units at specified
date. Crop planted in Jan., 1980. Homestead,
Florida . ... 97

22 Sample size and relative net precision (RNP) for
sampling TPW larval injuries on upper and lower
plant canopy. Homestead, Florida, 1980 .. 100

23 Sample statistics: Mean tomato pinworm larval in-
juries per plant in 8 tomato plantings. Homestead,
Florida, 1979-81 . ... 102

24 Mean tomato pinworm (TPW) foliar larval injuries
at 2 different plant levels for 3 different
plantings. Homestead, Dade County, Florida, 1980. 103

25 Mean tomato pinworm (TPW) larval injuries in 6
plant strata for 5 plantings. Homestead, Dade
County, Florida, 1981 . ... .105

26 TPW larval injury sample allocation for 6 plant
strata at 3 different plant stages: second repro-
ductive (TR2), third reproductive (TR3) and
senescent (S1) . . 113

27 Mean number and standard error of tomato pinworm
(TPW) injuries in 5 different plantings at speci-
fied date and plant growth stage ... 115

28 Tomato fruit damaged in the upper and lower plant
canopy, after a single artificial infestation with
K. lycopersicella larvae on ground tomatoes 124

29 Marketable value for tomato fruit damaged in the
lower and upper plant canopy after a single arti-
ficial larval infestation of K. lycopersicella
on ground tomatoes. . ... 125

30 Tomato fruit damaged in the lower and upper plant
canopy after a double artificial infestation of
K. lycopersicella larvae on ground tomatoes ... .126

31 Marketable value for the tomato fruit damaged in
the lower and upper plant canopy after a double
infestation of K. lycopersicella on ground
tomatoes . . ... .128


Table Page

32 Effect of planting time on fruit injured by
K. lycopersicella larvae to ground tomatoes,
cv 'Flora-Dade' during 1981 . 149

33 Differences in cost and relative net precision
between sampling 6 plants per row and 1 random
plant per row . ........ 150

34 Differences in mean fruit injured by K.
lycopersicella in pruned and not pruned
tomato plants . * 151

35 Effect of hedges and edgerows on tomato pinworm
field infestation at three fields in Home-
stead, Florida, 1981 . . 166

36 Parasitism of the tomato pinworm larvae in
tomato fields in southern Florida, Dade
County, 1980 . .. ...... 175

37 Parasitism of the tomato pinworm larvae in
tomato fields in southern Florida, Dade County,
1981 . . 177

38 Keiferia lycopersicella eggs parasitism by 2
strains of Trichogramma pretiosum in the
laboratory. T25+10C; 75+2% RH . 179

39 Number of Keiferia lycopersicella eggs col-
lected from two strata and percent of para-
sitism by Trichogramma pretiosum 1. 180

40 Distribution of normal and parasitized tomato
pinworm eggs in 2 tomato fields .. 181

41 Parasitism of tomato pinworm eggs by Tricho-
gramma pretiosum in 2 fields with different
host densities . ......... 183

42 Plant water content in five tomato plantings
related to oviposition by the tomato pinworm 203

43 Effect of simulated rainfall on foliar larval
injuries caused by the tomato pinworm Keiferia
lycopersicella on plants grown under greenhouse
conditions . .. ........... *

44 Mean percentage of tomato pinworm adults
emerged by day after pupal treatment with
different simulated rainfall regimes .. 208

Table Page

45 Effect of crop age of post-harvested tomato
plants on volunteer plants and number of tomato
pinworm larval injuries . ... 220

46 General effect of cultural practices on
volunteer tomatoes and infestation by
tomato pinworm . . ... 222

47 Effect of planting age and cultural practices
on volunteer tomato plants and number of TPW
injuries . . ... 223

48 Tomato pinworm egg frequency distributions
determined on tomato plants during 1981 ...... 244

49 Tomato pinworm foliar injury frequency
distributions determined on tomato plants
during 1980 . . ... .. 249

50 Tomato pinworm foliar injury frequency
distributions determined on tomato plants
during 1981 . . ... .. 253

51 TPW egg allocation sample for 6 plant strata.
Planting 8, 1981. Age: 38 days. Stage of
development TV .................. 258

52 TPW egg allocation sample for 6 plant strata.
Planting 8, 1981. Age: 46 days. Stage of
development TR .................. 259

53 TPW egg allocation sample for 6 plant strata.
Planting 7, 1981. Age: 68 days. Stage of
development TR2 . ... 260

54 TPW egg allocation sample for 6 plant strata.
Planting 4, 30 Oct. 1980. Age: 77 days. Stage
of development TR2 ................ 261

55 TPW larval injury sample allocation for 6 plant
strata. Planting 6, 1981. Age: 78 days.
Stage of development TR ............. 262

56 TPW larval injury sample allocation for 6
plant strata. Planting 5, 1981. Age: 108
days. Stage of development TR2 .......... 263

57 TPW larval injury sample allocation for 6
plant strata. Planting 4, 1981. Age: 120
days. Stage of development TR3 . ... 264


Figure Page

1 Illustration of tomato cv Flora-Dade growth at 2 stages
of development. TV2=second vegetative stage; TR1=early
reproductive stage; a=primary leaf; bilateral develop-
ment . . ... ....... .. .29

2 Influence of time on leaf area (dm2) expansion, flower-
ing and tomato fruit numbers of cv Flora-Dade grown
on 'Rockdale' soil under southern Florida conditions 39

3 Stages of development of tomato. TV1=early vegetative
stage; TV =late vegetative stage; TR, TR2, TR3=repro-
ductive stages; S =senescent stage .. . 41

4 Linear relationship between tomato pinworm (Keiferia
lycopersicella) larval head capsule width (mm) and
foliar injury length, r2=0.47. . ... 47

5 Linear relationship between tomato pinworm (Keiferia
lycopersicella) larval instars and visual leaf damage
scale, r =0.677 . . 50

6 Average number of tomato pinworm eggs per plant
stratum during 6 different sampling dates in 2 to-
mato plantings at different growth stages.
A) Planting 7: Jan. 30, 1981. B) Planting 8: Feb.
28, 1981. TR =second reproductive stage of develop-
ment; TV2=sec8nd vegetative stage of development.
Plant strata: 1, 2, 3: upper, middle, lower external,
4, 5, 6: upper, middle, lower internal .... 73

7 Frequency of tomato pinworm eggs at different distances
(cm) between eggs when mean eggs were A) 2 eggs per leaf-
let and B) 5 eggs per leaflet. . ... 85

8 Percentage of tomato pinworm (TPW) larval injuries in 2
sampling units from different plant portions, related to
number of injuries in the whole plant: 1) 1st planting,
Nov. 3, 1979; 2) 3rd planting, Jan. 8, 1980 ... 99


9 Percentage of tomato pinworm (TPW) foliar injuries found
at upper, medium and lower stratum in 4 tomato plantings:
1) Oct. 30, 1980; 2) Nov. 25, 1980; 3) Dec. 30, 1980; and
4) Jan. 30, 1981. Bars followed by different letters were
significantly different according to Duncan's Multiple
Range Test (P=0.05). Percentages were previously
transformed to arc sine. Percentages are expressed as
actual numbers before transformations . .

10 Percentage of larval injuries at the external and
internal canopy evaluated from 5 tomato plantings.
Plantings 4, 5 and 6 planted in Oct., Nov., and Dec.,
1980; Plantings 7 and 8 planted in Jan. and Feb., 1981.
Homestead, Florida, 1980-81 . .

11 Relationship between number of tomato pinworm
larvae per plant and number of injured fruits
and leaves in the lower plant canopy by a
single artificial infestation with TPW larvae.
Homestead, Florida, 1980-81 . .

12 Relationship between number of tomato pinworm
larvae per plant and number of injured fruits
and leaves in the upper plant canopy by a single
infestation of TPW larvae. Homestead, Florida,
1980-81 . . .

13 Relationship between number of leaves injured
in upper and lower canopy and number of fruits
injured in upper and lower canopy by a single
artificial infestation with TPW larvae. Home-
stead, Florida, 1980-81 . .

14 Relationship between number of larvae per plant
and number of injured fruits and leaves (upper
and lower canopy) after a double artificial in-
festation with TPW larvae. Homestead, Florida,
1980-81 . . .

15 Relationship between number of leaves injured
in upper and lower canopy and number of fruits
injured in upper and lower canopy by a double
artificial infestation with TPW larvae. Home-
stead, Florida, 1980-81 . .

16 Regression of percent of yield reduction
against infestation densities per plant of
tomato pinworm larvae . .

. 130

. 132

. 135

. 137


. 144




Figure Page

17 Regression of percent yield reduction of to-
mato fruit against TPW number of foliar
injuries per plant . ... 146

18 Abundance of tomato pinworm male moths at three
different field sites. A) Field 1, 1980; B)
Field 2, 1980; C) Field 3, 1981. Mean number
of moths at each site corresponds to the average
from 4 pheromone traps in north, south, west and
east directions. Homestead, Florida, 1980-81 .. 159

19 Mean number of tomato pinworm larval injuries
occurring in 4 commercial fields at 0, 30, and
120 m from the field border. Bars with the letter
"a" denote statistical differences at 0.05% dif-
ference level for a particular date . ... 164

20 Field plan: Fields 1, 2, and 3, respectively,
each field was divided into 8-9 quadrats. The shaded
areas represent higher insect populations. Home-
stead, Florida, 1981 . .. 168

21 A-B. Relationship of Keiferia lycopersicella
egg density to percent parasitism by Trichogramma
pretiosum in 2 fields . . 185

22 A-C. Seasonal occurrence of Keiferia lycopersicella
eggs and parasitization by T. pretiosum in tomato
fields located at the (a) northern, (b) middle, and
(c) southern areas of Dade County, Florida. ... 188

23 Seasonal abundance of TPW eggs in experimental
fields, related to temperature and rainfall
regimes during A) 1980, and B) 1981, in Home-
stead, Florida . .. 196

24 Seasonal abundance of TPW larvae in tomato fields,
related to temperature and rainfall regimes during
1980-81, in Homestead, Florida . 200

25 Mean number of TPW injuries per plant during 9
days of simulated rainfall under greenhouse con-
ditions, avg. daily temperature 25+20C .. 206

26 Percentage of TPW adult emergence under greenhouse
conditions after treatment of pupae with 3 regimes
of artificial rainfall (200, 100, 50 and 0 ml water),
temperature 24+30C .... . 210


Figure Page

27 Tomato field status following the main
harvest under S. Florida conditions. Home-
stead, Florida, 1980 . ... .216

28 Number of tomato plants and TPW injuries
per m in 2 post-harvested tomato fields.
Homestead, Florida, 1980 . ... .219


Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy




April 1983

Chairman: Dr. V.H. Waddill
Major Department: Entomology and Nematology

Experiments were conducted in Homestead, Florida, during 1979-1981

to describe tomato plant phenology, tomato pinworm (TPW), Keiferia lyco-

persicella (Walsingham), dispersion patterns, economic damage to tomato

and the effects of parasitoids, edgerows, rainfall and cultural practices

on TPW population dynamics.

Tomato cv. Flora-Dade phenology was described. Six stages were

designated based on the number of leaves, flowers, fruits and physiological

plant characteristics. This description can be of use in making pest

management decisions.

Based in the relative variation (RV) and sampling costs, sampling

units for TPW egg and larval stages were determined. Eggs were generally

(51%) found in the upper plant canopy, and larvae (50%) in the lower

plant canopy. Larger sampling units were allocated to the upper

and lower plant canopy for eggs and larvae, respectively. An

economic injury level was determined to be 1 larva per plant.

Yield can be reduced 10-40% when 1-12 larvae are attacking 45 day-old

plants. The results indicated a correlation between number of foliar

injuries in the lower plant canopy and fruit damage. In southern

Florida, higher TPW infestation occurred during March-May, 1980 and

March-April, 1981, compared with other months (Jan., Feb.). Trichogramma

pretiosum Riley caused 33-73% TPW egg mortality during May-July, 1981.

TPW larval parasitism fluctuated between 39-42% during 1980-1981. The

most abundant larval parasite was Apanteles spp., followed by Sympiesis

stigmatipennis and Temelucha spp.

TPW adult dispersion and effects of field edges on TPW dispersion

and field colonization were evaluated. Field areas surrounded by edge-

rows had higher TPW damage than areas surrounded by pastures.

The use of artificial rainfall demonstrated that when plant foliage

was irrigated there was a behavioral change in larval feeding which

resulted in 50% reduction of larval injuries compared to injuries on

soil-irrigated plants. TPW adult emergence was reduced 86% when high

levels of water were applied to pupae in the soil.

The effect of cultural practices on the TPW oversummering popu-

lation was evaluated. The mean number of injuries per m2 was 28 times

higher in crops planted later (December, 1980) than in crops planted

earlier (October-November, 1980). Lower numbers of injuries were found

in crops disced and mowed than in abandoned fields.

Parasitoids, cultural practices, and southern Florida climatological

patterns can have an impact on TPW population levels.



The tomato, Lycopersicon esculentum Mill., is one of the most popular

and important vegetables in the world (Purseglove 1968). Tomato produc-

tion in the U.S.A. is concentrated in California, Florida, Texas, New

York, New Jersey, Michigan and Virginia (Thompson and Kelly 1957).

Florida tomato acreage was 31360 ha during 1980-1981. Tomato produc-

tion is considered to comprise 28.31% of the total vegetable acreage

in Florida (Anonymous 1982). The tomato growing areas in Florida are

divided into 4 major districts: Palmetto-Ruskin, Pompano Beach-Fort Pierce,

Dade County and Immokalee-Naples (Anonymous 1981). Dade County has 18.3%

of the total state tomato production and supplies most of the winter (De-

cember through February) vegetables for the U.S.A.

The cultivation of fresh market tomatoes demands a high monetary in-

vestment from farmers. The cost of producing tomatoes in Dade County

during 1980 was $5123.25 per ha, which represents an increase of 1.44

times over the production cost of 1975 (Greene et al. 1980).

Expansion of tomato acreage in Florida resulted in changes of agro-

nomic practices to maximize tomato production (Geraldson 1975). Changes

in horticultural practices also established an agro-ecosystem with ento-

mological characteristics common to monocultures. From 1950-1975 insect

control in tomatoes was almost exclusively chemical. To help growers avoid

problems with insecticides such as insecticide resistance, secondary pest

outbreaks and objectionable pesticide residues, an integrated pest man-

agement program was established in Dade County on tomatoes (Pohronezny

et al. 1978). This program goal was to develop economically, technically

and ecologically sound systems of integrated pest management. This

approach had some constraints, however, such as the high crop value

which reduces the use of pest management tactics (Bottrell 1979). More-

over, the fruit quality standards for fresh tomatoes cause undue emphasis

on chemical control measures in order to prevent contamination of fruit

by insects and to prevent cosmetic damage to the fruit (Lange and

Bronson 1981).

Accordingly, insect pests in tomatoes can be categorized as direct

pests and indirect pests. Direct pests attack the product and directly

destroy a significant part of its value. Indirect pests attack plant parts

other than the saleable product but may reduce yield of the product (Ruesink

and Kogan 1975). Among direct pests of tomato in Florida are the corn ear-

worm, Heliothis zea Boddie, the southern armyworm, Spodoptera eridania

(Cramer), and the tomato pinworm, Keiferia lycopersicella (Walsingham).

Indirect pests are the serpentine leafminer complex, Liriomyza spp, the

tobacco hornworm, Manduca sexta (Joh.), and the granulate cutworm, Feltia

subterranea (Fab) (Poe 1972).

The tomato pinworm (TPW) can be either a direct or indirect pest

of tomatoes. The larva of this insect feeds in the mesophyll of the

leaves causing a serpentine-type mine during the first 2 larval instars.

In the latter instars the larvae can cause a blotch-type mine or they

tie leaflets together. The larvae also bore into fruit, providing an

entrance for plant pathogens which cause major damage to fruit.

The importance of the TPW as one of the most serious pests that

affect tomato production in semitropical areas of Florida has been docu-

mented by Poe (1974a) and Wolfenbarger et al. (1975). Tomato pinworm

incidence was noted in Florida as early as 1932 (Watson and Thompson

1932) with serious outbreaks occurring during 1942, and from 1970 through

1973. Several factors have been mentioned by Poe et al. (1975) as caus-

ing these outbreaks, i.e., type of insecticide used, change of tomato pro-

duction practices, and harmful effect of pesticides on natural enemies.

Other factors such as weather have been overlooked. Current practices

for TPW control in Florida have been almost exclusively chemical (Waddill

1975), although emphasis has also been given to breeding tomatoes for

TPW-resistance (Schuster 1977a) and less to TPW biological control

(V.H. Waddill, personal communication). The effects of several factors,

e.g., rainfall and cultural practices, that influence the life system of

the TPW are still not understood.

To develop effective integrated pest management for tomato, the

interrelationships among the crop (plant physiology, phenology), pests

(arthropods, weeds, pathogens) and environment (climate, natural enemies,

horticultural practices) must be carefully studied. It is necessary to

understand TPW ecology and basic biology by studying the role of several

factors that cause seasonal and annual changes in pest populations. The

ability to assess the presence and abundance of the pest by accurate

sampling techniques would permit a reliable study of TPW potential

for inflicting economic damage. By evaluating the role of extrinsic

factors, e.g., weather, natural enemies and agronomic practices, it may be

possible to reduce the TPW problem.

This study was initiated to answer these and related questions.

The specific objectives of research were:

1) to describe different stages of development of the tomato plant.

2) to evaluate techniques for tomato pinworm damage assessment.

3) to discuss sampling techniques for tomato pinworm immature
stages under southern Florida conditions and to describe TPW
spatial distribution.

4) to evaluate the importance and population dynamics of TPW
natural enemies.

5) to evaluate the effect of hedges and edgerows on TPW dispersion
and field colonization.

6) to determine a way to assess yield losses in ground tomatoes due
to TPW.

7) to determine the influence of rainfall on TPW population.

8) to study post-harvest field management practices that influence TPW

Therefore, the first chapter is a general literature review of

studies on K. lycopersicella and addresses the effects of biotic and

abiotic factors on the population dynamics of this insect. The

second chapter is a study of tomato plant phenology and also covers

the evaluation of foliar damage assessment techniques. In chapters III

and IV, I address sampling techniques and dispersion patterns of tomato

pinworm eggs and larvae. The fifth chapter deals with the effect of

tomato pinworm infestation on upper and lower parts of the plant. In the

same chapter I state the relationship between TPW population index and

yield losses. In chapter six I address the distribution of male moths

and larval stages in tomato fields, and the effect of edgerows in such

distribution. In chapter VII, I deal with the abundance of egg and

larval natural enemies of the tomato pinworm.


The interaction of rainfall and TPW is presented in chapter VIII.

Finally, I evaluated the data regarding horticultural practices

and the relationship between changes of tomato agroecosystem and

oversummering populations of tomato pinworm (chapter IX).


Family Gelechiidae

The family Gelechiidae is one of the largest of the microlepidoptera

(about 580 North American species). Larvae vary in habits. Some are

leafminers, a few form leaf galls, many roll or tie leaves, and one

species, Sitotroga cerealella Olivier, is an important.pest of stored

grains (Borror et al. 1976). Studies on crop pests in this family have

been concentrated on pests of high economic importance, such as the pink

bollworm (Pectinophora gossypiella Saunders), the potato tuberworm

(Phthorimaea operculella Zeller), the angoumois grain moth (S.

cerealella), and Keiferia lycopersicella Walsingham, the tomato pinworm.

The pink bollworm and the potato tuberworm are generally considered

good colonizers with highly mobile behavior within and between fields

(Stern 1979, Van Steenwick et al. 1978); however, many experts considered

these moths weak fliers which move great distances by being carried pas-

sively by air currents (Kaae et al. 1977). They are capable of having

several generations per year, with the last generation showing a strong

dispersal tendency (Kaae et al. 1977). The potato tuberworm is perhaps

the most closely related to the tomato pinworm in patterns of behavior

and plant selection (Hofmaster 1949). Several authors (Shelton and

Wyman 1979, Meisner et al. 1974, Traynier 1975) have studied factors

influencing oviposition of potato tuberworm and the relationship between

populations of the pest and the host plant. Their studies were used as

a base in this research to compare with K. lycopersicella population


Studies on Keiferia lycopersicella (Walsingham)

The tomato pinworm (TPW), K. lycopersicella (Wals), is frequently

confused with other species (Povolny 1977), particularly with Scrobipal-

pula absolute (Meyr.) and Phthorimaea operculella (Zell.) (Doreste and

Nieves 1968), since they are also considered pests of potato and tomato

(Povolny 1973). K. lycopersicella and S. absolute are apparently iso-

lated from each other geographically and ecologically. K. lycopersicella

apparently avoids the cordillerian territory of the northern and southern

part of South America (Garcia et al. 1974, Mallea et al. 1972, Quiroz 1976).

The range of K. lycopersicella is in the eastern part of the American

continent and penetrates into Central America, Mexico (Povolny 1973) and

the U.S.A. (Elmore and Howland 1943). Phthorimaea operculella has been

reported on tomatoes in Venezuela, (Doreste and Nieves 1968), Bermuda

(Grooves 1974), and Egypt (Abdel-Salam et al. 1971).

In the U.S.A. K. lycopersicella is considered a key pest of tomatoes

in western California (Oatman 1970), Texas, Florida, Pennsylvania and

Hawaii (Swesey 1928, Thomas 1933). The tomato pinworm was first recog-

nized as a pest of tomatoes by Morrill (1925), and was later reported by

Elmore (1937) and Thomas (1933). In Florida, the TPW has been primarily

studied by Watson and Thompson (1932), Swank (1937), and recently by

Poe (1973). The seasonal history of the TPW was reported by Elmore

and Howland (1943) in California where it appears first during March

and April after overwintering in the pupal stage at or near the surface

of the soil. Later studies of the seasonal occurrence of TPW in Cali-

fornia showed that larval populations increased abruptly in September

and October (Oatman et al. 1979) and in April-June (Oatman 1970).

Batiste et al. (1970b) reported that there is no evidence for diapause in

this insect. Destruction of the tomato plants shortly after harvest may

prevent the insect from surviving the winter and infesting the crop

during the following season. Poe (1974a) reported that on the west coast

of Florida, severely infested fields occurred in the spring crop (February-

May) with less damage on plants during the autumn. Early infestations in

greenhouses also lead to heavy losses in the field.

Host Plants of Keiferia lycopersicella

Elmore and Howland (1943) reported that tomato and potato are pre-

ferred hosts of TPW. Several solanaceous plants, e.g. eggplant ISolanum

melongena (L)] and nightshade (Solanum nigrum L.), also are known hosts

for the TPW (Batiste et al. 1970b, Elmore and Howland 1943, Swank 1937,

Thomas 1933). Batiste and Olson (1973) demonstrated that K. lycopersicella

preferred tomato for oviposition over 12 other solanaceous plant species.

TPW could be reared on Solanum melongena L., S. dulcamara L., S. nigrum, and

S. elaegnifolium Cav. but not on S. nodiflorum Jacq., S. douglasi Dunal,

Datura meteloides A., D. stramonium L., D. ferox L., Nicotiana biglovii

(Torr.) and N. glauca Grah. The same author suggests that in California,

Solanum melongena, S. dulcamara and S. elaegnifolium may play a role in

the population dynamics and distribution of TPW.

Life Cycle of Keiferia lycopersicella

Accounts of the life history and behavior of K. lycopersicella have

been reported by Elmore and Howland (1943), Swank (1937), and Poe (1973).

Poe (1973) found that eggs are laid singly or in groups of two or

three on the host plant foliage. Elmore and Howland (1943) described the

egg as ellipsoid, 0.37 by 0.23 mm, light yellow when first deposited, grad-

ually darkening to a light orange before hatching. Eggs hatch 4-9 days

after deposition (Swank 1937) at 20.680C and after 4-4.5 days at 27-290C

(Elmore and Howland 1943). Weinberg and Lange (1980) determined that

eggs hatch in a range of 3.5 + 0 days at 350C and 7.8 + 0.2 days at


Keiferia lycopersicella has four larval instars (Elmore and Howland

1943, Swank 1937). Head capsule width of the larval instars are 1st in-

star 0.14-0.157 mm; 2nd instar 0.23-0.28 mm; 3rd instar 0.364 39 mm;

4th instar 0.52-0.61 mm (Elmore and Howland 1943). Newly hatched larvae

averaged 0.85 mm in length. The head capsule is dark brown and the re-

mainder of the body is a yellowish gray common to many newly hatched

lepidopterous larvae. The mature larvae are 5.8-7.9 mm in length and

characterized by an ash gray color with dark purple spots (Elmore and

Howland 1943). Larvae of K. lycopersicella characteristically possess

a pale prothoracic shield with conspicuous dark fuscous shading along

lateral and posterior margins (Capps 1946). Duration of the leaf mining

(1st-2nd instars) stage ranges between 4.7-5.8 days. The leaf folding

stage lasts between 5.6-16 days for a range of temperatures of 13-29 C

(Elmore and Howland 1943). Weinberg and Lange (1980) found that egg

hatching to pupation times range from 8 + 0.9 to 18 + 1.6 days when

reared at 350C.

The pupae are initially green, later turning to a brown typical

of lepidopterous pupae commonly found in the soil (Elmore and Howland,

1943). Before pupation the larvae form a loose pupal cell of sand grains

at a depth of 0.25-1.5 inches beneath the soil surface (Poe 1973). Wein-

berg and Lange (1980) recorded that pupation requires 11.3 + 0.5 at 20 C,

and 5.1 + 0.2 days at 350C. The length of the pupal stage was 38.7 and

11.4 days at temperatures of 12.65 and 26.4 C (Elmore and Howland 1943).

Swank (1936) obtained a range of 7-17 days with an average of 11 days

for the pupal stage at 260C.

Adults are characterized by an alar expanse of 9-12 mm. Labial

palpi have a short forrowed brush on the underside of the second joint,

a terminal joint somewhat thickened with scales, and are compressed

with the extreme tip pointed. The head and thorax are mottled with

dark brown. Forewings are elongate ovate, the hind wings have a

pointed apex, a strong pencil of hair scales, are dilated at tip of costa

in females, and dilated from base of costa in the males; the abdo-

men is dark fuscous above with basal joints slightly ochreous, the

underside is light ochreous sprinkled with dark fuscous spots. Adult

longevity is 7 days (24 + 20C) when they are fed on water and 8.5 days

at 240 + 20C when fed a 10% honey solution. At temperatures of 10 and

13C the respective longevities were 20.5 and 22.8 days (Elmore and

Howland 1943).

Insect Behavior

Elmore and Howland (1943) reported that copulation occurs within 24

to 48 hrs after moth emergence, and McLaughlin et al. (1979) stated that

sexual activity such as female calling was greatest during the 1st hr

of darkness. Very little copulation occurred after the 3rd hr. Males

ran or walked in their approach to calling females. Approach was gener-

ally from behind or at ca. 900 to the female and was accompanied by rapid

wing fanning. The copulatory strikes of the males were made laterally

beside the females. Moths remained in copula from 30 min to 2 hr.

Elmore and Howland (1943) and Poe (1973) described the behavior of

larval stages of K. lycopersicella. Newly closed larvae disperse briefly

from the hatched egg before entering the leaf. First instar larvae

spin a tent of silk over themselves and tunnel into the leaf. Further

feeding results in a blotch-like mine. The 3rd and 4th larval instars

feed from within tied leaves, folded portions of a leaf, or they

may enter stems or fruits. The 3rd instar appears to be the most

mobile and several types of behavior may occur (Poe 1973). This stage

larvae can draw 2 leaves together, may tunnel into stems or fruits at

the calyx, but usually the larvae form leaf folds on the upper leaf

surface. The four instars can cause injury to 3-6 leaves during develop-

ment (Poe 1973).

Elmore and Howland (1943) demonstrated that larvae that have mined

calyx lobes and nearby tissues enter the fruit instead of folding leaves.

Usually, the larvae enter the fruit beneath the calyx lobes or fruit

stems, but in heavily infested fields about 50% of the injured fruit may

be damaged in other places as well. The damaged areas caused by shallow

feeding just beneath the skin of the fruit appear as blotches. Larvae

that enter the fruit penetrate to a depth ranging from 0.9-1.9 cm.

Differences in the phenology of larval injuries were studied by

Batiste et al. (1970), who found that mines of the early stage larvae

superficially resembled the serpentine type mines produced by dipterous

leafminers of the genus Liriomyza. The mines could be distinguished

easily, because the dipterous leafminer leaves a trail of frass within

the mine, whereas the TPW larvae deposits nearly all the frass in a

single mass at the tunnel entrance.

Tomato Plant Resistance to TPW

Breeding for resistance work with tomatoes has largely been con-

cerned with pathogens, but currently there is a renewed emphasis on

insect resistance as part of integrated pest management (Lange and Bronson

1981). Resistance to many tomato insects does occur and includes resis-

tance to the fruitworm, Heliothis zea (Cosenza and Green 1979); leaf-

miners, Liriomyza spp. (Schuster et al. 1979); tomato pinworm, K. lyco-

persicella (Schuster 1977a); hornworms, Manduca spp (Kennedy and Henderson

1978), Colorado potato beetle, Leptinotarsa decemlineata Say (Schalk and

Stoner 1976; potato aphid, Macrosiphum euphorbiae (Thomas); flea beetles;

white flies (Aleyrodidae); spider mites (Acarina) and many others (Lange

and Bronson 1981). The mode of resistance in tomato is complex and may

involve many factors including antibiosis, preference, phenological devel-

opment (such as flowering time, time of fruiting, etc.), morphological

characteristics, presence or absence of foliage pigments, foliage vol-

atiles, and physiological incompatibility.

Resistance to the tomato pinworm has been studied by Schuster (1977a),

Schuster et al. (1979), and Kennedy and Yamamoto (1979). Schuster (1977a)

found that accessions of Lycopersicon sculentum Mill x L. pimpinelli

folium were more susceptible, while those of L. peruvianum (L) Mill, L.

peruvianum var. humifusum Mill., L. esculentum x L. peruvianum, L.

cheesmani f. minor (Hook F) Mull., and L. glandulosum Mull., were less

susceptible than the commercial cultivar 'Walter' (L. esculentum Mill.).

Selections of L. hirsutum Humb and L. hirsutum f. glabratum Mull. were

more resistant and had 25-50% and 50-75% less damage respectively

than 'Walter'. In laboratory studies the same author found that mine

lengths after 2 days were significantly shorter for PI numbers 129157

(L. hirsutum f glabratum) and 298933 (L. peruvianum). Schuster et al.

(1979) stated that levels of resistance to tomato pinworm and vegetable

leafminer appeared to be intermediate and the varieties PI 12930 and PI

1404403 of L. esculentum were found moderately resistant to both insects.

Kennedy and Yamamoto (1979) found an extractable toxic factor in the

foliage of L. hirsutum f. glabratum affecting Manduca sexta, H. zea, K.

lycopersicella, Aphis craccivora, A. gossypii, and Myzus persicae. Schuster

(1977b) reported that tomato varieties 'Pennorange E 160 A' and 'Pearson'

had less fruit damage by K. lycopersicella and armyworms, primarily

Spodoptera eridania (Cramer), than did the 'Walter' variety.

Chemical Control of TPW

Chemicals are widely used to control tomato pests. The need for

insecticides varies from year to year and from one area to another (Lange

and Bronson 1981). Chemical control of TPW was obtained in 1943 by Elmore

and Howland (1943) who recommended synthetic cryolite and talc dust

(50% sodium fluoaminate). In California, several insecticides were

evaluated by Middlekauff et al. (1963) and reevaluated by Batiste et al.

(1970a). The latter authors reported little or no control of larvae by

insecticides applied as soil treatments under greenhouse conditions.

These same authors stated that methyl parathion was the most effective

material in greenhouses, and also recommended parathion, methidathion,

phosphamidon, mexacarbamate and methamidophos. Spray deposits of para-

thion were found by the same authors to be significantly less effective

against eggs or early stage larva than was toxaphene-DDT.

Poe and Everett (1974) presented results of experiments to control

TPW in 2 locations in Florida. They reported that granular insecticides

in general did not perform as well as most spray materials for reduction

of the TPW mines and larvae in tomato transplants. They recommended

acephate, diazinon, endosulfan, and methomyl to keep seedlings nearly

mine free. Chlordimeform was co::isidered phytotoxic to seedlings but when

sprayed alone or combined with Bacillus thuringiensis Berliner on older

plants gave good control of TPW larvae without plant toxicity. Poe and

Everett (1974) recommended highly residual insecticides to maintain a crop

free of damaged fruit.

Waddill (1980) reported that certain insecticides used on demand

for tomato pinworm in Homestead, Florida, significantly reduced TPW

damage below that in the untreated check. Permethrin +

Bacillus thuringiensis were applied least often and were among the best

treatments. The author also showed that when used on demand a low rate

(0.225 Ibs ai) of methomyl resulted in significantly more damage than

the same rate plus 0.5 Ibs Bacillus thuringiensis.

Schuster (1977b) reported that when measured by the number of

damaged fruit, the degree of control of the TPW and southern armyworm

with Bacillus thuringiensis WP and chlordimeform was significantly depen-

dent on the tomato cultivar. The contact toxicity of 4 synthetic

pyrethroids and methomyl to some adult parasites of tomato pests indi-

cated that fenvalerate was generally the least toxic to parasites com-

pared to permethrin, burethrin, and NRD1C49 (+)-d-cyano-m phenoxybenzyl

(+) cis, trans-3-(2,2 dichlorovinyl)-2-dimethyl-cyclo-propanecarboxylate)

as well as methomyl (Waddill 1980). Fenvalerate was judged the most

promising candidate for use in a pest management program in tomatoes for

integrated control of the TPW and the vegetable leafminer. Lindquist

(1975) obtained the best control of TPW with synergized pyrethrins (MGK

pyrethrins) and endosulfan.

Emergence of K. lycopersicella and Apanteles spp from pupae and

soil treated with insect growth regulators (IGR's) resulted in 23%

suppression of pinworm adult emergence when applied directly to the TPW

pupae but was ineffective when applied to the soil. The IGR's caused a

reduced emergence of the parasite Apanteles spp from 61% to 0% (Poe

1974b). Prada and Gutierrez (1974) reported some results on microbial

insecticide control of Scrobipalpula absolute, the South American pinworm.

Seventy five to eighty percent control of the pest was obtained within

5-100 days after treatment at the rate of 500-200 Neoplectana carpo-

capsae Weiser nematodes per plant or with Bacillus thuringinesis (150-

500 g/ha). Schuster (1982) demonstrated that a mixture of B.

thuringiensis and Coax (454 g + 1.8 kg product/378 Its) when applied to

TPW infested tomato seedlings, increased TPW mortality up to 42.2%.

Cultural Practices for TPW Control

According to Lange and Bronson (1981), the mechanization of pro-

duction of processing tomatoes has not only revolutionized the industry

but has altered many control techniques and as a result, a few formerly

major pests have been reduced to a secondary position. Elmore and How-

land (1943) considered some cultural practices as undesirable because of

their adverse impact on TPW control. These include failure to destroy aban-

doned plantings, careless disposal of infested culled fruit, and use of

infested seedlings. In Florida, Swank (1937) recommended that all mate-

rial remaining in the field after the crop is harvested be carefully

plowed under. He suggested that the carelessly abandoned fields could

become a reservoir for infestation of a nearby or succeeding crop. Poe

(1973) stated that the best control for TPW is based on several cultural

practices: use of non-infested seedlings, destruction of plant debris,

use of light traps for adults in small areas, and destruction of plants

growing from seeds in compost heaps. Price and Poe (1977) reported that

staking and artificial mulching of tomato plants reduced damage caused by

K. lycopersicella and other pests.

Biological Control of TPW

Employment of biological control measures for insect and mite pests

of row crops has been limited, and the poor record probably relates

largely to the short-lived row crop environment, which presumably does

not permit establishment of the effective host-natural enemy relation-

ships which often characterize more stable environments (van den Bosch

et al. 1976). Modern-day biological control techniques have not been

fully exploited in tomato under field conditions (Lange and Bronson

1981). They have been widely accepted in European glasshouse tomato pro-

duction, however. Reports on parasitism of K. lycopersicella were

made by Elmore and Howland (1943), Swesey (1928), Thomas (1933), Oatman

et al. (1979) and Poe (1973) (Table 1).

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Cardona and Oatman (1971) studied the biology of the larval para-

sitoid Apanteles dignus Muesebeck which is a solitary, primary, larval

endoparasite of K. lycopersicella and found that the total developmental

time from egg to adult was ca.18 days at 26.6 + 10C and 50 + 2% RH. Oat-

man (1970) stated also that the most common parasites at both Indio and

Escondido (California) during 1963-64 were A. scutellaris (Mues.) and

Parahormius pallidipes (Ashm.) followed by Sympiesis stigmatipennis

Girault. The biology of A. scutellaris (Mues.) was studied by Djamin

(1970). In California, A. dignus apparently occurs only along the coast

in the southern part of the state. Studies conducted by Oatman et al.

(1979) determined that in the south coast there was a range of larval

parasitization of 1.6-36.8% during 1972-73. Apanteles dignus was the most

abundant parasite reared from larvae followed by S. stigmatipennis Girault.

In Florida, Poe (1974b) reported that 50-70% of tomato pinworm larvae in

leaflets collected in the spring, 1973 were parasitized by Apanteles spp.

Behavioral Chemicals Used in Monitoring and Control of TPW

Pheromones. Sex pheromones of the adult TPW were obtained by

Antonio (1977) from extracts of the whole body of 2-day-old virgin fe-

males. A biological assay method was then devised to test males for

optimal response to the pheromone under varying conditions. Field evalu-

ation data by the same author indicate that the natural sex pheromones

were attractive to male tomato pinworm moths. McLaughlin et al. (1979)

found that males were more responsive when bioassayed with dim light

from both above and below an olfactometer than when illuminated only

from below. The effect of trap design and sex attractant release rates

on TPW catches was studied by Wyman (1979). It was determined that Zoe-

con Ic sticky traps were 6 times as effective in capturing TPW males as

were Delta sticky or mineral oil traps. An inverse relationship between

attractant release rate (fibres/dispenser) and trapping efficiency was

found. K. lycopersicella positively responded to a sex attractant of

unstated composition dispensed from rubber septa in traps in a tomato

field (Wyman 1979).

Deterrents. Beck and Schoonhoven (1980) stated that surface testing

of insects touching or piercing with the ovipositor or by biting and

probing with the mouth parts is in response to chemical factors that act

as incitants. If the stimuli received on initial testing indicate an

unacceptable plant, the behavior pattern is interrupted and the insect

abandons the plant. Such stimulants are deterrents.

Schuster (1980) reported that survival of TPW was reduced when larvae

fed on excised tomato leaflets dipped in solutions of cyhexatin, fentin

hydroxyde (triphenytin hydroxide) and guazatine (SN-513); N-n'''-(iminodi-

8,1-octanedilyl) bisguanidine. These compounds protected foliage and

fruit from insect damage when plants were sprayed in the field.

Tomato Plant Phenology and Measurement of TPW Dispersion and
Economic Damage

Little information is available that relates tomato plant phenology

to pest management or that concerns dispersion and economic damage of

the TPW. Plant phenology related to pest management tactics has been

determined already for different crops: alfalfa, cotton, potato, tobacco,

soybeans, etc. (Anonymous 1971, Reynolds et al. 1975, Ambrust and

Gyrisco 1975, Johnson 1979, Fehr et al. 1971). Tomato plant phenology

as related to pest management has been reported by Alvarez-Rodriguez

(1977) and Keularts (1980). Alvarez-Rodriguez (1977) evaluated pest

(pathogens and insects) damage as it is related to tomato life table

analysis and determined strategies for tomato production. Keularts

(1980) determined the effect of artificial defoliation in plants 30-100

days old. These studies should have been complemented by a phenological

description of the plant at different plant stages.

Studies of measurement and description of dispersion of TPW popu-

lations must involve a sampling program in which biological, statistical

and economical aspects of the program are evaluated (Southwood 1978).

This information is expected to result in 1) biological interpretation

of statistical parameters and 2) the use of this knowledge for measuring

of TPW control and for establishing a reliable scouting program.

Sampling designs for tomato pinworm larval stages have been studied by

Wolfenbarger et al. (1975) and Wellik et al. (1979). Wolfenbarger et

al. (1975) developed a sequential sampling program based on the detection

of larval feeding on the 3 top leaves per plant. Alternatively Wellik

et al. (1979) found that lower leaf and large fruit sampling methods

were best for detecting the presence of TPW. These opposing results

demand more detailed research in order to obtain more accurate TPW

density estimates.

The data concerning tomato pinworm damage range from estimations

of damage based on pesticide effectiveness (Batiste et al. 1970a, Poe

and Everett 1974, Waddill 1975, 1980), damage evaluation based on

effectiveness of parasitism of TPW larvae (Oatman 1970) to estimation

of economic injury levels (Wolfenbarger et al. 1975). Poe and Everett

(1974) determined the percentage of unmarketable fruit as 6.5 to 4%

when the plant was untreated. Waddill (1980) reported that plants

without chemical control may lose up to 75% of the fruit. Oatman (1970)

determined tomato fruit was infested up to 70% despite 68.9% larval

parasitization. Wolfenbarger et al. (1975) reported that an average of

0.3 TPW injuries per 3 top leaves caused 20% injured fruit.

Environmental Factors Affecting TPW Population

Characteristics of Agroecosystems

Agroecosystems vary widely in stability, continuity, complexity

and area. The kind of crops, agronomic practices, changes in land use

and weather are important elements affecting the degree of stability of

an agroecosystem (Stern et al. 1976). Since agroecosystems are

characterized by a short life (Loucks 19701, they are more susceptible

to pest damage and catastrophic outbreaks. This also occurs because of

a lack of diversity in plant species, insect species, and sudden alter-

ations imposed by man such as plowing, mowing and use of insecticides

(Luckman and Metcalf 1975, Pimentel 1961a, b, Smith 1970, van Emdem and

Williams 1974).

Tomato Agroecosystem

The tomato crop is a typical example of an agroecosystem with early

community succession (Price and Waldbauer 1975). In southern Florida 3

closely related tomato varieties are generally grown: MH1, 'Walter'

and 'Flora-Dade' (Volin and Bryan 1976). Horticultural practices are

characterized by direct-seeding in the field through mulched beds

that will aid in maintaining a regular amount of soil moisture, weed

control, and fertilization of the crop (Geraldson 1962, Davis et al.

1970, Bryan et al. 1967). In summary, the tomato crop is typical

of agricultural systems with high community energetic, small or low

community structure, rapid nutrient cycling, selection pressure

(r selected, many small progeny), and quantitative progeny production.

Also, the tomato agroecosystem is characterized by having a few major

key pests and secondary pests (Lange and Bronson 1981). Most of these

pests, e.g., lepidopterous larvae, stinkbugs, dipterous leafminers,

whiteflies, leafhoppers, aphids and some species of beetles, are con-

sidered as r selected species with rapid development, high maximal rate

of increase (rm), early reproduction, small body size, many small off-

spring and short length of life (Krebs 1978, Pianka 1978).

Biotic and Abiotic Factors Affecting Insect Population Dynamics

Biotic and abiotic factors exercise some influence on the fluctu-

ation in the number of insects in time and space. To reveal both char-

acteristics the inherent property of animals themselves and environmen-

tal conditions in their habitats must be studied (Shiyomi 1976). Among

the biotic factors, we should consider the habitat effect on insect

distribution. Effects of habitat have been studied by several research-

ers: Gossard and Jones 1977, Lyons 1964, Brazzell and Martin 1957, Yama-

moto et al. 1969, Wolfson 1980, Sparks and Cheatman 1970, Dethier 1959a,

Nishijima 1960. They demonstrated the effect of habitat on oviposition

and adult and larval dispersal. The effect of sheltered zones on

distribution of insects has been demonstrated by Lewis (1979) van Emdem

(1965) and Price (1976). They indicated the importance of crop edge

effect on colonization and dispersal of arthropods, especially for r

selected species, which show a "safety in numbers" strategy for progeny

reproduction and survival. Van Emdem (1965) considered that unculti-

vated land in regard to the insect fauna of a crop has 2 components:

1) Physical: shelter-survival in debris of woodland, 2) Biological:

plants of uncultivated land provide alternate food and breeding sites for

injurious insects, crop diseases or alternate hosts for predatory and

parasitic insects.

In most agricultural environments the principal pests are usually

controlled to a greater or lesser extent by natural enemies (Messenger

et al. 1976). The efficiency with which such natural enemies suppress

pest populations is influenced on the one hand by their own intrinsic pro-

erties and limitations and, on the other hand, by environmental factors

and conditions occurring in the agroecosystem under consideration

(Messenger et al. 1976).

Among the abiotic factors affecting insect populations, weather

and climate are commonly accepted by entomologists as dominant influ-

ences on the behavior, abundance and distribution of insects (Messenger

1959). Effects of climate on insect populations were studied by

Richards 1961, Nicholson 1958, Cloudsley-Thompson 1962, Andrewartha and

Birch 1974. Most authors agree that 2 of these factors, temperature and

RH possess a high degree of interaction and affect insect activity and

survival. As an example Chapman et al. (1960) and Hofmaster (1949)

have looked upon the effect of climate on survival of Gelechiidae.

Finally, pest control in an agroecosystem can be aided by proper use

of cultural practices. Two basic principles in the cultural control of

arthropod pests are 1) manipulation of the environment to make it less

favorable to the pest and 2) manipulation to make it more favorable for

their natural enemies (Stern et al. 1976). Cultural methods, however,

require a thorough knowledge of crop production and the biology and

ecology of the pest and its natural enemies in order to integrate the

techniques for pest control into proven agronomic procedures for crop




Description of tomato plant phenology and evaluation of tomato pin-

worm larval presence are major aspects of tomato pest management that need

to be determined. First, studies on tomato taxonomy, growth and develop-

ment, effects of fruit on vegetative growth, and relationship between

fresh weight and leaf area are well documented (Cooper 1964, Murneek

1924, Hurd et al. 1979, Romshe 1942, Thompson and Kelly 1957, Purseglove

1968). However, tomato crop phenology that divides the growing plant

into characteristic periods and shows the relative time in each period

needs to be studied. Second, description of TPW damage to the foliage

and TPW mine length correlation with plant resistance has been studied

by Elmore and Howland (1943), Batiste et al. (1970) and Schuster (1977).

Nevertheless, the evaluation of different techniques for TPW foliar

injury assessment is necessary to establish a relationship between larval

instars and amount of damage.

The objectives of this study were first, to define growth character-

istics of tomato plant during a typical southern Florida growing season,

second, to describe from a pest management point of view the phenology

of tomato, cv. Flora-Dade, and third, to determine constraints and prac-

tical use of TPW larval population indices.

Materials and Methods

The Tomato Crop

Tomatoes, cv Flora-Dade, were planted in 1979 (Nov. 3, Dec. 5),

1980 (Jan. 8, Oct. 30, Nov. 25, Dec. 30), and in 1981 (Jan. 30, Feb. 28)

at the University of Florida, Agricultural Research and Education Center,

in Homestead, Dade County, Florida. After metribuzin was incorporated

into the soil at a rate of 0.84 kg ai/ha, beds 45 m long were prepared

and fertilized with 7-14-14, at a rate of 2242 kg/ha. Immediately after

fumigation, drip tubing for irrigation was placed ca. 15 cm into the soil

and the beds were covered with plastic mulch. Tomato seeds were planted

with a seed drill 30 cm apart in the rows. One to two weeks after emer-

gence, the seedlings were thinned to one per hill. Plants were protected

from pests by application of fenvalerate 2.4 EC (.045 kg ai/ha), maneb and

tribasic copper sulfate (0.97 + 5.71 ai kg/ha) at weekly intervals.

Two to five plants were selected at random from each of the 8

plantings, and height, leaf area, number of leaves, suckers, flowers and

fruits were recorded every 8-15 days.

Description of Stages of Tomato Plant

The method used to describe tomato plant phenology was based on

the technique of Fehr et al. (1971) for soybeans, Glycine max (L).

Three developmental stages of tomatoes were defined: vegetative,

reproductive, and senescent. Number of leaves, plant height,

time of blooming and fruit formation were averaged from the 8 plantings.

Development of the plant was quantified by a nomenclature system, where

primary leaves were numbered from the bottom to the top; any secondary

growth, e.g., formation of primary laterals (Fig. 1), had the same node

number from which it originated, and it was distinguished with a let-

ter(s). The stem that originates from the bifurcation of the main stem

was called a secondary main stem (2M); laterals that develop from primary

laterals were considered secondary (2S).

Methods of Damage Assessment for TPW Larvae

A set of 3 tomato plants 40-50 days old grown in 20 cm pots was

introduced every 2 days into a cage (45 x 45 x 60 cm) for oviposition

by moths previously held at 24 + 30C and RH 75 + 2%. Plants were subse-

quently removed, and set aside for larval development. When each set of

plants was under attack by 1-4 larval instars, a total of 100 damaged

leaves was taken to the laboratory for inspection. A total of 20

individuals was studied per instar. Three methods of measurements were

used in separate experiments. First, a portion of leaf area mined by

the TPW larvae was separated from the leaf and then measured on a

LICOR model LI3100 area meter. For another set of damaged leaves,

leaf weight ingested by the larvae was determined by measuring the dif-

ferences in weight between the damaged leaflet and the juxtaposed leaf-

let. Larval instar in both experiments was determined by measurements

of the larval head capsule width. Second, a visual classification of dam-

age was made of leaf damage caused by TPW larval instars. A five class






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scale of 0-4.5 (Table 2) was devised, based on personal observations and

the damage descriptions of Batiste et al. (1970a).

The leaf injury length (cm) was also measured and larval head capsule

width recorded. Finally, the presence or absence of TPW larvae in different

types of leaf injury was determined. A simple linear regression model was

used to examine the relationship between the head capsule width and injury

length, and between larval instar and the damage rating scale. The eval-

uation of the different methods of damage assessment was discussed with

regard to the practicality of their use for scouting programs.

Results and Discussion

The Tomato Crop

A summary of leaf area and number of flowers and fruits is shown in

Table 3. Tomatoes planted during October, 1980 began to flower 61 days

after plant emergence and fruit set occurred at 73 days. Maximum leaf

area was reached at 134 days. Tomatoes planted during November, 1980

started blooming at 54 days, and fruit set occurred at 68 days. Maximum

leaf area occurred 88-112 days after plant emergence. Tomatoes planted

during December, 1980 and January-February, 1981 had a shorter vegetative

period, with flowering at 42-62 days and fruiting at 49-62 days. Leaf

area reached a maximum at 63-89 days. The total leaf area during these

plantings was lower than that produced from fall plantings.

Under southern Florida conditions, average temperature changes

drastically from autumn to early spring (Mitchell and Ensign 1928). In

this area, the effect of planting date determines growth and tomato

Table 2. Classification of tomato pinworm leaf damage on 'Flora-Dade'
tomatoes, based on greenhouse and field observations. Home-
stead, Florida, 1980.

Degree of Damage Description

0 No damage

1-1.5 Mining of leaves, ca. 0.50 cm or less in

length; mine narrow and elongate; tissue

transparent; mine on any part of the leaf-

let; some leaves attacked by more than 1

larva; small larvae present.

2-2.5 Mining of leaves ca. 0.51-0.68 cm; 1/4 of the

mine is necrosed, but changing to a raised

area or oblong to ovoid blotch; frass accumu-

lation at the bottom of the injury.

3-3.5 Blotching of leaves; blotch necrosed over

60% of the injury; no holes indicating lar-

val exit; size 1-2 cm; epidermis of the leaf

opaque to chlorotic due to larval injury to

midvein; construction of silk tent in epi-


4-4.5 Leaf folded; fold can occur at any lobe of

the leaflet. Necrosis extended to 75-80%

of the leaf; extensive frass accumulation

on blotch or fold; injury length 2-4 cm.

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development. Tomato, cv Flora-Dade, was developed for production of

fresh market tomato fruit (Volin and Bryan 1976) during the months of

January-March. Consequently, planting before or after the autumn

months of October-December resulted in a high reduction of leaf area

and yield.

Developmental Stages of Tomato

Vegetative growth of the tomato plant passed through 3 distinct

phases (Fig. 2). In the first phase there was a steady increase in leaf

area, while in the second phase leaf area was relatively constant. The

third phase was characterized by reduction in rate of leaf expansion 130

days after plant emergence. The number of inflorescences rose rapidly to

a peak at 70 days and then steadily decreased, whereas fruit reached a

peak at 90 days post-planting and then steadily decreased. Flowering and

fruit formation were observed at 40 and 50 days, respectively. Three

major developmental stages were determined for tomatoes: vegetative,

reproductive and senescent (Fig. 3). Each stage was divided into sub-

stages. Each substage is explained in detail in Table 4.

The characteristics of tomato plant growth (Fig. 3) demonstrate the

relation between leaf area and crop age (days after emergence). The in-

crease in leaf area was observed until half of the second reproductive

stage (TR2). Leaf area is reduced during the third reproductive stage

(TR3) and senescent stage (S ). I consider that the TR2 stage can be

subdivided into another stage. This will allow a more detailed descrip-

tion of plant stages, as well as shorter time periods for better assess-

ment of pest management.


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Table 4. Stage of development description for tomato cv Flora-Dade.
Description is based on the average of observations from
tomato plants grown during Fall 1980 through Winter 1981.
Homestead, Florida.

Plant Stage








Tomato Plant Description

Plants 1-15 days old. Complete formation of

2-3 primary leaves; loss of cotyledons; plant

height ca. 5-7 cm.

Plants 16-35 days old; plant erect (12-16 cm);

5-7 leaves, development of laterals; plant

with only 1 main stem.

Plant 35-40 days old; development of laterals

from nodes 1-5; at leaf 4-5 the stem bifurcates

producing another stem as vigorous as the first

main stem; production of floral clusters at

node 5 and second main stem; height 50 cm.

Plants 67-70 days old; fruit set; plant postrated;

yellowing of primary leaves.

Plant 109-135 days old; 90% fruit ripe; post-

harvest maturity; at least 60% of the primary

leaves necrosed, development of secondary laterals

at nodes 3-5; plant totally postrate; height ca.

32-57 cm.

Table 4--continued.



Plant 140-200 days old; dead leaves on main

stem and second main stem; regrowth of plant

from auxiliary buds at nodes 1,2 and produc-

tion of up to 3 floral clusters may occur;

possible fruit development.

The principal application of this nomenclature system is to deter-

mine the amount of yield reduction produced by damage inflicted at given

stages of plant development. As an example, if I use Keularts'(1980)

data from his experiment in tomato defoliation, 20% defoliation of lower

plant leaves at stages TV1 through TR2 did not alter mean yield

per plant. However, 20% defoliation of upper plant leaves at TR2 stage

caused yield reduction. The nomenclature system can apply to single plants

or entire crops. It would be worthwhile to apply this system to other

tomato cultivars.

Methods of Damage Assessment for TPW Larvae

Average leaf area and weight consumed by TPW larvae. The data from

this experiment demonstrated the complexity of measuring TPW foliar dam-

age. The average leaf weight (mg) and leaf area (cm2) consumed by larvae

of a determined instar are shown in Table 5. Average leaf area consumed

ranged from 0.5 to 1.57 cm2 for 1st to 4th instar. First and fourth

instar larvae consumed 5 and 13.42 mg of leaf, respectively. Variance of

leaf weight measurements was large suggesting that many uncontrolled

factors influence feeding of individual larvae in the field. Either

method might be used for laboratory and greenhouse experiments where the

researcher would have more control of the factors influencing variability

(e.g., leaflet size, leaf age).

Length of Foliar Injury and Use of Damage Scale

Length of foliar injury and TPW head capsule width were cor-

related (r=0.68; P=0.001, F=39.33) (Fig. 4). Furthermore, there was


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a significant relationship between TPW (Fig. 5) larval instar and the

degree of damage observed (r=0.79). Both techniques suggest the possi-

bility of prediction of damage level in the tomato plant at stages

TV1 TR1. Such a prediction may be influenced by other factors such

as plant stages and larval density.

The use of larval instars to determine injury length has a reduced

bias compared to use of TPW damage degree scale. Foliar injury measure-

ment is only advisable for research experiments (e.g., plant resistance,

pesticide screening) in which the time frame available to determine the

dependent variable is not a constraint. Other aspects to be considered

for further study are larval preference for larger or smaller leaflets,

as well as presence of different larvae in the same leaflet.

The use of TPW damage scale is perhaps less precise than the tech-

nique mentioned above. Damage scale technique may introduce personal

error in measurement of larval instar in relation to degree of damage.

It is possible, however, to use this technique as an adjunct aid to the

population index (number of injuries per plant).

As an example, using the equation y=0.80 + 0.795x, where y = the

leaf injury damage scale and x = the tomato pinworm larval instar; if

the value of x equals 3, the average degree of damage in the plant will

be 3.18. This information will help to determine the effect of the

insect in economic terms, once the economic threshold is reached for

plant stages TV TR At this point there is no information available
1 1
for TPW EIL values for plants in these early stages. Therefore, further

studies will be necessary to indicate that the presence of a particular

larval instar is capable of producing a determined economic damage.









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The ratio of percentage of larvae present to percentage of larvae

absent (Table 6) in the observed injuries was 4:1 for the folded necrosed

injuries, 31:1 for the folded with no necrosis, 1:3 for blotches with

necrosed tissue, and 3:1 for transparent blotches. Consequently, the

use of necrosed blotches will indicate that ca. 77% TPW larvae will be

absent from the observed blotches. If a high number of injuries per

plant falls in this category, the probability of not measuring

larval presence in each injury is increased. We can deduce that necrosed

tissue generally indicates that larvae are already attacking the fruit or

other leaves, or have left the canopy to pupate.

In a crop such as tomato where the margin of profit is great,

expensive methods of control are usually dictated. The use of a system

that will predict the damage level to the plant requires a high level of

accuracy. It is suggested that the method described here is advisable

for plants during stages TV1 to RV1.

Conclusions and General Discussion

Studies of tomato growth in different cropping seasons are useful

to determine effect of planting time on plant development. Tomatoes,

cv Flora-Dade, planted later in the winter have less (ca. 117 dm2)

leaf area than those planted early in the fall (ca. 253 dm2 leaf area).

Thus, those crops planted in October-November may be able to support

more damage than those planted in January-February. The proposed system

divides the plant stages into 2 vegetative stages (TV1 TV2), 3 repro-

ductive stages (TR1, TR2 and TR3), and a senescent stage (S ). The

description of the developmental stages of tomato can aid in using pest

management tactics. Definition of shorter developmental stages with

Table 6. Percentage of tomato pinworm larval occurrence in foliar
injuries with different phenological characteristics.

Damage Description

Percentage of TPW Larval Occurrence
Present Absent

Transparent blotch 72.5 27.5

Necrosed blotch 23.3 76.6

Folded, no necrosed leaf 96.87 3.12

Folded, necrosed leaf 81.25 18.75

with more subdivisions would enhance phenological plant description.

This may allow better pest monitoring when plant development is in the

TR stage.
Results on leaf weight consumed (mg) and leaf area consumed (cm2

provided information on increments of those parameters for each larval

instar. Standard error and confidence intervals demonstrated a high

variability for both methods. Further research is necessary to deter-

mine if such variability is caused by larval behavior or by use of

different leaflet sizes and leaf area. I consider the leaf weight

method promising in such areas as plant resistance and behavioral

chemicals (deterrents) evaluation. Damage assessment based on the

leaf area mined by TPW is not considered appropriate for monitoring

TPW density because of inherent variability in insect behavior and

plant morphology.

Injury length has proven useful in evaluating plant resistance

(Schuster 1977a). The relationship between larval head capsule

and injury length was intermediate (r =0.47). The regression equation

developed in this study can be used by plant resistance evaluators to

determine feeding inhibition at a given instar. This technique has

to be carefully used, however, since it is dependent on the type of

leaflet consumed. Larvae that attack small leaflets might develop as

well as one in a large leaflet but the injury length will be smaller.

Data gathered from the visual damage classification proved to be

useful to evaluate damage inflicted by TPW. Since TPW instars have a

distinct behavior as leaf blotchers and leaf tiers, it will be easier

to develop knowledge in which the average larval instar will determine

the damage degree in a plant.


Scouts should use different techniques at the same time if

possible. A population index, degree damage scale and a survey deter-

mining the real presence of the larvae in the foliage will provide a

better estimate than a single technique. More research is needed to

evaluate these techniques together. Evaluation should be based on time

expended and reliability of the methods. Further study of the relation-

ship between several types of foliar damage and direct damage to the

tomato fruit is needed.



Tomato pinworm (TPW) is one of the most important pests of tomato

Lycopersicon esculentum (Mill.) (Watson and Thompson 1932, Oatman 1970,

Poe et al. 1974). Little is known, however, about ovipositional pat-

terns of this pest on tomato plants under field conditions. There is

some indication that caged moths under laboratory conditions deposit

eggs indiscriminately on all parts of the plant including the upper

leaves (Elmore and Howland 1943). Wellik et al. (1979) indicated that

lower portions of the plant should be examined in the field for both

larvae and eggs of the TPW.

Studies of TPW egg dispersion are necessary because this knowledge

affects the sampling program as well as the method of analyzing the

data. Furthermore, dispersion patterns can be used to give a measure

of population size as well as to describe the factors that may affect

the condition of the population. This paper (1) describes the spatial

distribution of TPW eggs on field-grown tomato plants under varying

levels of TPW infestation, (2) presents an evaluation and discussion

of factors affecting this distribution and (3) discusses sampling


Materials and Methods

Experimental Plots

To test for a possible relationship between oviposition of TPW and

different leaf strata of tomato cv Flora-Dade, 8 plantings (Oct. 3, 1979;

Dec. 5, 1979; Jan. 8, 1980; Oct. 30, 1980; Nov. 25, 1980; Dec. 30, 1980;

Jan. 30, 1981; Feb. 28, 1981) of non-staked tomatoes were evaluated at

the Agricultural Research and Education Center, University of Florida,

Homestead, Florida. Each planting (ca. 450-947 plants) was direct-seeded

in raised beds (3-5) (ca. 45 m long) of Rockdale soil, and mulched with

light colored plastic. The seedbed's midlines were 182 cm apart. Plants

were spaced 38 cm apart.

Sampling Methods

Sample size was selected by a preliminary random sampling of 50

plants on 2 dates. The method described by Elliott (1979) was adopted.

The relative variation (SE/x) x 100) was calculated to compare sam-

pling methods over a variety of sampling units (Hillhouse and

Pitre 1974, Ruesink 1980). Ten to twenty plants in each planting

were randomly selected on a weekly basis from February 7, 1980,

through May, 1980, and from Jan. 27, 1981, through May, 1981. Whole

leaves of the plant were first examined to determine differences in ovi-

position on lower and upper leaf surfaces (Plantings 1-3) and to detect

differences in oviposition in different plant strata (Plantings 1-8).

A plant was divided into upper half and lower half in the first 3

plantings (1979-80) and divided serially into 6 sections (upper, middle

and lower of each of the external and internal canopies) (1980-1981).

External canopy was defined as extending from the periphery to 5-15 cm

into the plant interior. The variance was stabilized by fitting the

number of eggs obtained to a suitable model (Poisson and negative

binomial) and transforming to logarithm (x+l) or x+0.5 (Elliott 1979)

depending upon the original frequency distribution of the counts.

The mean counts of eggs in upper and lower strata were compared by

student's t-test for plantings 1-3. Egg densities in the 6 strata for

plantings 4-8 were compared by analysis of variance (ANOVA). Means

were grouped by Duncan's Multiple Range Test (P=0.05). When tests

indicated significant differences in egg densities between strata of

plantings (4-8), optimum sample allocation among strata was determined

for each planting date (Cochran 1977).

Population Distribution Related to Leaf Position

To test differences in oviposition of TPW related to the vertical

distribution of the leaves with respect to the main axis, 17 randomly

sampled plants, each of which were 45 days old, were observed in a

commercial field. Leaves were numbered from bottom to top and the num-

ber of eggs recorded. Data were analyzed by ANOVA and means were separated

by use of Duncan's Multiple Range Test (P=0.05). When t-tests indicated

significant differences in egg densities between leaves, optimum sample

allocation among leaves was determined (Cochran 1977).

Distances Between Eggs and Effects on Distribution

To determine if TPW egg distribution pattern is influenced by leaf-

let size and egg density, the frequency of egg deposition on each

leaflet was recorded. Then, distance between eggs on each leaflet was

counted on 40 middle leaves collected from plants located in the same

field mentioned before. Several authors (Cottam and Curtis 1956)

proposed methods to evaluate randomness in spatial distribution of the

population by measurement of distances between individuals. In this

experiment, distance between eggs was checked by measuring the shortest

straight line between nearest neighbors with a metric ruler. Distance

accuracy was 0.05-0.25 cm. The frequency of occurrence of each dis-

tance was evaluated for egg densities. Also, simple linear regression

was applied to determine any relation between egg density and leaflet


Oviposition Related to Plant Age

To determine if plant age affects oviposition, the number of eggs

on each plant was counted on 60-80 plants ranging in age from 2 to 21

weeks. Plants in this experiment were in the same field as previously

described tests (plantings 4-8). Plants were inspected weekly during

April and May, when the highest peaks of oviposition occurred. Data

were subjected to ANOVA, and means separated by use of Duncan's Multiple

Range Test (P=0.05).

Results and Discussion

Selection of Number of Sample Units

The main objective of planning a survey should be to obtain the

required information with a minimum amount of labor. To achieve this,

it is necessary to select a number of sample units that are in agreement

with the desired degree of precision and cost. This requirement is

difficult to meet in practice. First, an acceptable index of precision

(SEx100) is 25% (Barfield 1981). Secondly, the actual cost of sampling
tomatoes is 7 dollars per acre (Table 7).

Sample size was selected by a preliminary random sampling of 50

plants in 2 dates (Table 6). Three major criteria were followed to

select sample size. First, following the criteria outlined by Elliott

(1979), a suitable sample size was selected when the mean value ceased to

fluctuate. It is observed (Table 5) that with an increase in sample

size from 10 to 25 (at low egg density), the resultant mean (x)

fluctuates around 0.4-1.5 eggs/plant. Also, at higher egg density (2-7

eggs/plant) the number of selected sampling units is 20-25. Second,

the use of index of precision (SExlOO) over different sampling units is
a more adequate technique to select sample unit size.

Accordingly, the lower index of precision (Ip) was obtained when

the number of samples equals 50. Therefore, the percentage of the

standard error of the mean can be 34% if the TPW egg density per plant

is low (0.4-1.5 eggs/plant). This percentage is not good enough to make pest

management decisions. The index of precision can be 20% if the density is

higher (2-7 eggs/plant). Third, the sample number does not reconcile with

the actual budget per acre. Cost of sampling eggs is 1.4-77 dollars

(Table-5) more expensive than the actual sampling cost per acre.

The number of samples for a fixed level of precision (random sampling)

was calculated. A random egg distribution was assumed, n=(=-)2 where,

n=number of samples required, s=standard deviation, x=mean, and

E=predetermined standard error (e.g., 0.25). For instance, at

N0 Ckm'
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0- CO


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o a' O> (oF W
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m Ion c F

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rl lO

01 M M01 0

-H NL- N L -i HN N NU'

q 0-
5 -I


m0 *

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(I 0
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endemic levels of TPW egg population (0.4-1.33), the number of samples

to be taken, being S=2.79, E=0.25, x=1.15 will be 94, with a cost of

158 dollars per acre. If the TPW egg population is epidemic (2.16-7),

the number of samples to be taken will be 28, being s=3.82, x=2.9 and

E=0.25. The cost of sampling will be 47 dollars per acre.

Accordingly, under low TPW egg densities, increasing sample

precision as the sample size increases is not worth the work required

in taking larger samples. Consequently, I selected sample sizes of

10-20 which gave the best practical results per unit of work expended

($16.8-25.2 dollars per acre). It is considered that sampling TPW

eggs is not a practical method to make spray decisions.

Statistical Description of TPW Egg Spatial Distribution

The use of statistical methods, e.g., t-tests, analysis of vari-

ance, involves several conditions described by Snedecor and Cochran

(1967). One of them is that data must follow a normal distribution.

The distributions of density measurements on plant samples are sum-

marized for each planting in the Appendix. These statistics (Table 8)

support the hypothesis that TPW eggs are clustered on plants. This

clustering was more apparent when TPW egg densities on each plant

ranged from 0.302-1.3. As mean densities increased, variance also in-

creased except for planting 6. Values of the negative binomial parameter

(k) (Elliott 1979) range from 0.451-0.013 for my sampling. Thirty-two

percent of the weekly counts for each planting were fitted to the nega-

tive binomial distribution (see Appendix). For plantings with higher















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m m
(N N

o c


N m
Lfl (n

m m
rOl 0

o o

o o
co co

Hn o

o 0u

N a3

N 01

M coN

i-i (m m '' I' '0 Nr co


-4 I I
I- I I

ix cN


c.' N

* *

o I

0 m0

m Lf
r^ t~

> 0 0
0Z 0) (
z lz I-

population densities (average 0.302-1.30), kurtosis and skewness

decreased as the mean increased. Skewness values were all positive.

This indicates that egg distribution tails off among higher counts.

This information in conjunction with the data indicating clumping can

aid in sampling design.

Distribution of Eggs on the Upper and Lower Surfaces of Leaves

Statistically significant differences (P=0.01) were found for egg

numbers on lower and upper leaf surfaces. Eighty-nine percent of

the total eggs found per plant were on the lower surface (Table 9).

These results and the results from the greenhouse contrast with those

found in caged plants by Elmore and Howland (1943), who detected 45%

of all egg deposition on the upper surface of the leaves. Insect pre-

ferences for oviposition on the underside might be correlated with dif-

ferences in pubescence of the 2 leaf surfaces. The average number of

trichomes on the underside was 1441 per leaflet as opposed to 469 on

the upper surface. This may also indicate preference to avoid egg

desiccation, or to avoid higher light intensities during oviposition

(Hinton 1981).

Distribution of Eggs on Upper and Lower Halves of the Plant

Statistically significant differences (P=0.05) were found in the

number of eggs deposited on the upper half of the plant vs the lower half

of the plant for the 3 sample dates in the first planting (Table 10). The

upper part of the plant had more eggs on 13 of the 15 sampling dates.

There were no significant differences between upper and lower halves

Table 9. Ovipositional preference of tomato pinworm
for upper and lower surfaces of tomato
leaves from plants grown under greenhouse
and field conditions.

Mean Number of Eggs of TPW
Leaf Side Fielda Caged Plantsb

Upper 0.857c 0.10c

Lower 7.3763 2.77

aMean based on counts from 80 plants.
Mean based on counts from 60 plants.
Numbers were significantly different at P=0.001.


- 0 C
(fl 03? l a a
~- 02 .0

C Cn C C C
0 -1 M0
n3o 3 '
-14 44 M C;

T L i
00 c

W4 0
0O I 02 .0

T3 > -; ^ C.'.i ,

-4"- I v o i m
CLD MJ 1 N N O 3 O iI)

=w -
4 c 0

0 J

4-) M 1 0 ao 0 0 0 =
2 I 2 N C C 2

_ m N 4J~4. Z4C ; 0
io J

4-) W w-w
ma '"'>
r. 71 0 .

e w .. n c c
HO^ IU N 02 rN C N -I 0

4-4 00 1
.4 .4i c N 4 02 'C

.N N 'V
4J > 1 y.
01 hn a
0 0
tu "' Q ~ m o o -i o .S

C LA 0 0 C -4 0 jj --
N **1 O O
0 m
o I, a3

q u) 3 4 I* C L 0 C
H n i to 0) c)

*- m S o o o o o C -i 0
0 r- o w i

0 ) 02 0
g ~~ (UrO O O O OO .^1

0 -c 0

N- C C 0 3C C
M -

40 0 C

0 C3 0

4. Lj r^co D*
r 300

3C C

4 -4

3 a) 3 0
2( 0- -. C a a
C C rC

E- 3 l
4- L-r I. 44. 4- 4- 0

I ~ 4 -- .
0)0 02 02 02 02 02

(u *" 1 I 3

cr- i u, "i m i
g -C
02 02 2) 02 02 C LI

C I .-- 2
0) .ca c 024

.0 02 02 C
2 ,

in the second planting (Dec., 1979). Analysis of the data from the third

planting (Jan., 1980) indicated significant differences in 6 of the 11

sampling dates. The upper half of the plant had more eggs except for

2 dates. In general, when numbers of eggs were higher in the lower

strata, this coincided with younger plant age (40-60 days after germin-

ation). Numbers of eggs were higher in the upper strata when plants

were in reproductive or older age (75-80 days after germination. These

data indicated that for 'Flora-Dade' ground tomatoes, ovipositional

preferences existed based on the level of the plant. Because of the low

economic threshold for TPW in tomatoes, it may be necessary to reduce

the sampling unit to detect major differences in internal and external

parts of the plant when populations are low. Consequently, smaller

sampling units were tested in subsequent experiments.

Distribution of TPW Eggs by Sampling Six Plant Strata

Statistically significant (P=0.05) (Table 11) differences were not

detected among the strata for the 4th (Oct., 1980) and 5th (Nov., 1980)

plantings possibly due to the relatively low mean egg numbers per plant.

However, the highest number of eggs oviposited was obtained in the upper

external canopy for planting 4 and in the middle internal canopy for

planting 5. There was an increase in eggs for the lower internal canopy

in planting 4 during January and February, when nocturnal temperatures

were lowest (20C), and an increase toward the upper external portion of

the plants when temperatures were fluctuating between 17-290C (April-May).


I o c o o c C

-- 0 0 C C

4^ a; C 0 0 00

0I C C
1 C C > 0 0 0 0

r 4J o c o o o C

S- c o o o o o o o o o

0o a o O C 0 c 0 C

-4 c c c 0 c,
4I 0 0 0 0 0 0 C C
() 0

& ar o C C C C
d C C C C

S c 0 0 c 0 0 0 c
^l 0 3 Tl O O O= O C C 0 0 C
c-1 C C C C CI

O o o o o o o c c a o c

Sa0 4.

O 01 C 0 a c c 0 ) C)
a o o U) C c o

1 C r 0 0 C 0 0 0

r o 0 I o o o C o

I -
0 C "0 0 0 0

M 4 0 Ln 0) C
a )l w

S0 0 0 0 0

E -1
,-t c o

c3' '

S 0 0
0 0 C 0 0 C

3o O 0 C C C

C C C' C C

c C 0 0 0C

0 0 C0 0 0

(N r 0 4 CO
30 0 0 0 0

- -~ c o o c
S- C C 0 0
0 0 C 0 0

'C c Un c 0 0

C 0 0 0 C

S 0 C
SC in C C

0 u C C 0 C C

S- l C 0

0 C 0 a C 0
(- N r- 4") (.

0 C C 0 C 0

C 0 0 0 0 0
0 0 0 0 0 C

0 0 0 C 0 0

4 -4 -r)

4-4 X A C. .-) 4( -.4 4- -
X x )( X CV X C C.
. Cl *t *- C) C '-4 *
C) C) C) C)
4. -^ U< .. UJ U- .- U- Ur i-l
. "c C) C) "C C) C) "C C. C) 'C C)
C. 3 3) C) C3 C C. C^ C) "C C)
C. % 5' C. C.' C. C *-
= C. C c

-a a -a
'2 'a a 'o
in c o
(J (N '- (N

0 0 0 0

a a a a
o ^ nt
- (N IN (N
o 0 0 0

a3 a a

o 0 0 0


C i C '2

C C C 4 C

4 4 X 24 C C

Il L1 U *'-1 *
I 1) '2
_i 4 -< 4. 44 -
'2. '"2 "2 3


I t














U u
-4 '

'2 ,
'2 S
-4 -

'? 1
'2 <
3 C

- -
C .3

*' 2
'B a
** a,

S~ E
-S j

-' 2
'i2 2

o -

"' -
4--. Ci

42 -

a ;3

fl 3 -J
~u n-i
C a
'2 '2 o

3 i =

1) 3 0
a z 3
ji 41

Perhaps moths protect themselves from the cold temperatures by staying

close to the ground in the lower canopy. Despite these assumptions,

when number of eggs found per stratum was regressed (Table 12) against

temperature, there was no evidence of a relationship between the two

variables. Significant differences in numbers of eggs per stratum were

detected for the 6 (Dec., 1980), 7 (Jan., 1981) and 8 (Feb., 1981)

plantings. There was no significant variation among the six strata

during juvenile plant stages. Most of the significant differences were

observed (Fig. 6) during the mature stages (TR) of the plant. Concen-

trations of eggs in the upper external strata varied slightly among

plantings. In plantings 4 and 5, eggs generally occurred on the top and

middle external canopy during the last weeks of sampling (April and May),

and on all strata during the first weeks (juvenile stages) in March and

April. When mean numbers of eggs in the external and internal canopy

were added to reduce the strata to 3 (upper, middle and lower), no statis-

tical differences were observed despite the stratum reduction. This

agrees with the results expressed when 2 strata (upper and lower) were

sampled, indicating that differences in oviposition tend to be masked

if the units are widened. In general, the upper external stratum had the

highest number of eggs, followed by the middle external and internal strata,

during most of the sampling dates. At plantings 6 to 8, the TPW eggs

occurred in greatest abundance on the upper and middle external strata dur-

ing all growth stages. More eggs (44-68%) were deposited within the upper

external canopy of the plant than in any other stratum (Table 13). Four to

twenty eight percent of the eggs were laid in the next (middle external

stratum). The lower external stratum had the lowest range (1-11%); however,

Table 12.

Relationship between daily mean temperature (C) and TPW
oviposition in 6 tomato plant strata. Homestead, Florida,

Independent Variable
Variable No. Eggs/stratum ** ***
x y r r bo bl

Temperature upper internal 0.05 0.22 -0.007 0.005

upper external 0.13 0.36 0.46 0.04

middle internal 0.10 0.31 0.10 0.01

middle external 0.02 0.14 0.02 0.0056

lower internal 0.01 0.10 0.10 -0.02

lower external 0.13 0.36 -0.11 0.01

Coefficient of determination.
Correlation coefficient.
Intercept of y axis.


4 *. O

4- 0 0
H ** >

4t) r. 0)

-i > 0a

LO -4
S3 0) ( d

0 4--1 N
0) 4

3) cd-4
0)0 CC O

04 .) 4

H Cd c(0 3 0
CH H 0

4 -4 4J

-4 O4
Ha 0 0

n -4 0' 0

o o 40)
Ot QC( -4
0) *) 4-3 (o

(4 (1) -4
04 4 r4 a)
m 4 4-1 0

O tn 0-
4 *a 0)
C N 4J M 5

4 *a C
O4) ECrO M)

in 7 in
f0 W =3'




U I--


,n $ s/ u/



C= t c
r- -n %J



c Ln

- o S/S u

mn o -S /so e o ua

unto Jt/s 3 B Q u oay4

Table 13.

Percentage distribution of TPW eggs for each stratum of
tomato plants in 5 tomato plantings. Homestead, Dade
County, Florida, 1980.

Planting Date
Oct. 30 Nov. 25 Dec. 31 Jan. 30 Feb. 28
Stratum 1980 1980 1980 1981 1981

Upper external 68 32 44 46 51

Middle external 4 15 23 28 21

Lower external 1 3 10 11 10

Upper internal 0 3 7 0.6 5

Middle internal 9 43 11 10 9

Lower internal 16 0.8 4 1 2

growth of the plant upwards and outwards can mislead my interpretation

of actual ovipositional preference. The percentage of eggs found per

internal stratum ranged from 0-7% in the upper internal, 9-43% in the

middle internal, and 10-87% in the lower internal. TPW oviposits mainly

in the upper external canopy when egg populations range from 0.75-1.5

and when the plant was in its reproductive stage. A lower proportion of

eggs was found in all other strata.

Sampling 6 plant strata demonstrated that TPW tends to oviposit

in the middle and upper canopy. It is necessary to use sample allocation

(nh), as outlined by Cochran (1977) to minimize sampling cost or vari-

ance (s 2). I assumed equal sampling cost for each stratum. Sample

allocation was estimated on dates in which statistical differences in

oviposition were detected.

In general, more samples should be allocated to the upper and middle

external strata (Table 14). Because TPW eggs are clumped in the upper

and middle canopy, these strata had the highest variance (see Appendix)

(Tables 51-54). For a fixed total cost, n = (C-C ) NhSh where (C-C )=
o C-, o

L Nh Sh/ C
I C.n., nh= n W Sh n NnSh Therefore as S- increases so does nh.
ii hh= h. h
i=l WhSh ENhSh

The average number (n=20) for all planting dates was 6, 5 and 3 samples

from upper, middle and lower external canopy, and 1, 4 and 1 from upper,

middle and lower internal canopy. Allocation ranged from 5-10 samples

for the upper external canopy (see Appendix), and ranged from 2-8 samples

for the middle external canopy. I considered this sample allocation to

to be the best, because standard error (SE) of the sample mean was more



a4 r-

cy u

r- a)

*d U)

C ,4


o :

0 -,
0 0

-4 4


(0 -

, -I



O O m N -I 0 0 0 -I 0 0 0 N r-4

^ CO
in tn
o o 0 (Nn n

C O r-0 o 0 or- CN


0 0 %
Lo n NON
(N In :T I 0 m CO in 'o 'r N In (N In

n o ao0 L'L '.0


(N ,-4 (N (N CN C4 (N (N (N cN (N (N (N 0)
I oC o o C o C













en s -

constant through time (range: 0.20-0.66). There were exceptions for

these sample allocations. For instance, during the month of February

(planting 4), more numbers of samples were allocated to the lower inter-

nal stratum (see Appendix) (Table 54). Another aspect that requires more

understanding is the relation between phenological stages and sample

allocation. As an example, it was observed (see Appendix) that when

plants were in vegetative stage (TV), more samples (nh=18), should be

allocated for the upper external and middle internal canopy. When

plants are in first reproductive stage (TR ), more samples (n =61, are

allocated for upper external stratum. Finally, when plants reach the

second reproductive stage (TR2), all strata had similar sample allo-

cations except for lower internal canopy (nh=0).

Egg Distribution Influenced by Leaf Position

During heavy oviposition (avg 21.94 eggs per plant) on 45 day-old

tomato plants, the highest number of eggs was observed on leaf number 4

(Table 15). The numbers of eggs on leaves 3 and 5 were statistically

equal to those found on leaf 4. The number of eggs decreased sharply on

leaves adjacent to the apical point toward the bottom of the plant

(leaves 1-2). Tjese results indicated that middle leaves of 45 day-old

plants under conditions of high egg oviposition (1-5.5 eggs per leaf)

have 65% of the total egg population. These data differ from those

obtained in experiment 1. The higher number of eggs per plant indicates

that the insect tends to oviposit in the upper-middle canopy, avoiding

the 2 top and bottom leaves of the plant. Several factors may influence

the ovipositional pattern. First, these results agree with Hinton (1981),

Table 15. Mean tomato pinworm eggs on tomato leaves from different
strata of 45 day-old plants. Homestead, Florida, 1980.

Mean No. No.
Leaf Position Eggs/Leaf Leaflets/Leaf Eggs/Leaflet

1 bottom 2.20b* 7 0.31

2 3.20a 8 0.40

3 middle 5.40a 11 0.49

4 5.50a 11 0.50

5 5.00a 11 0.45

6 top 2.00b 8 0.25

7 1.00b 7 0.14

Numbers followed by different letters were significantly differ-
ent statistically at P=0.05 according to Duncan's Multiple Range

who stated that species that lay eggs on plants have a marked preference

for laying a certain height above the ground. Secondly, the insect may

be avoiding overcrowding in the smaller top leaves and competition of

foliar consumption by TPW larvae on the lower leaves. The highest

sample (n=17) allocation was for leaves in the middle canopy (Table 16).

Higher variance (s2=44.4) was found for eggs deposited on those leaves,

as was a high mean (x=6.6). This is caused by egg clumping in the canopy.

The fourth leaf had the highest allocation sample (nh=5), followed by the

fifth leaf (nh=4). The lowest allocation was for the bottom leaf (nh=l).

The standard error of the mean sample was lowest (SE/x=0.21), for the

third leaf and slightly higher (SE/x=0.24) for the fourth leaf. There-

fore, when higher density and large variance are found, the leaves

selected should be the middle ones. Sample allocation was reduced for

bottom and top leaves. These leaves had smaller variance and smaller

density than the middle ones.

Distances Between Eggs per Leaflet and Effect on Distribution

In the present study, the results indicated that TPW egg density

was not related to leaflet area (Table 17). The coefficient of deter-

mination (r2=0.026) indicated that females tend to oviposit different

egg densities disregarding leaflet size. Therefore, any leaflet can be

selected as the sampling unit. Frequency of egg occurrence per leaflet

was not related to distance between eggs. Low coefficients of deter-

mination (r2=0.19-0.23) between frequency of occurrence at different egg

densities (2, 5 and 10 eggs/leaflet) and egg distances indicate lack of

linear relationship between these variables. The slope (bl) obtained












-.~ o in o
o 10 oN 0

N in o N o
oco um

N w I I) c
IX En e \ .c

n H n H
m m 0
H D N.

co o ON o

0 0 N
I m ON oN

m 0 m
C 0 N 0
in o m o
i-i~ r

^r m o
*q o TI (

c o m o




i ^

Table 17.

Relationship between frequency of occurrence of TPW eggs per
leaflet as dependent variable and distance among eggs and
leaflet area as independent variables.

2* ** ** t
Dependent Independent r r b b1
Variable Variable
y x

No eggs Leaflet area 0.026 0.16 1.99a 0.04

2 TPW eggs Distance among 0.23 0.48 1.75a -0.15b

5 TPW eggs Distance among 0.19 0.44 1.47a -0.12b

10 TPW eggs Distance among 0.23 0.48 1.38a -0.22b

* 2
r =coefficient

of determination.

r=correlation coefficient.
bo=intercept of y asis.

numbers were highly statistically significant (P=0.01).
numbers were statistically significant (P=0.05).

for any egg density was negative and highly significant (P=0.001). This

can be explained in Fig. 7, where the frequency of egg occurrence at dis-

tances higher than 3 cm was as low as 5%. The average distance between

eggs was 0.5-0.75 cm. The average number of eggs found on each leaflet

was 2-3. These results agree with those expressed by Poe (1973); in the

present study the number of eggs on each leaflet was as high as 11.

Eggs tended to be laid more uniformly in some parts of the leaflet. Per-

haps the female lays 2 eggs successively on a certain part of the leaf-

let, but is likely to move away after oviposition. The arrangement of

eggs may also be a reflection of heterogeneity of conditions among parts

of a leaflet such as pubescence and leaf venation. From the practical

standpoint, these results can be used to determine use of single leaflets

as less variable sampling units compared to the whole plant. A more

detailed study of female behavior is necessary to determine the role of

leaf factors (e.g., pubescence) affecting oviposition.

Differences in Oviposition Related to Plant Age

The relationship between oviposition and stage of plant development

was determined during the study of plantings 4-8. Statistical differ-

ences were detected among these plantings (Table 18), when plantings

were 19, 15, 11, 7 and 3 weeks old (stages S1, TR2, TR TV2, TV1 respec-

tively. The largest number of eggs was detected in planting 7, when

this planting was in the TR TR2 stages. At the same time, egg num-

bers decreased for planting 6 after the 10th week of plant growth. The

mean number of eggs in planting 8 increased slightly from week 3 (TV2),

through 7 (TR ). These data indicate that there may be several factors,