Seasonal abundance of defoliating lepidopterous larvae and...

SEASONAL ABUNDANCE OF DEFOLIATING LEPIDOPTEROUSLARVAE AND PREDACEOUS ARTHROPODS AND SIMULATED

DEFOLIATOR DAMAGE TO PEANUTS

ByJOHN ROBERT MANGOLD

A DISSERTATION PRESENTED TOUNIVERSITY

N PARTIAL FULFILLMENT OF THEOF DOCTOR OF

UNIVERSITY

THE GRADUATE COUNCIL OF THEOF FLORIDAREQUIREMENTS FOR THE DEGREEPHILOSOPHY

OF FLORIDA

1979

ACKNOWLEDGEMENTS

The author wishes to acknowledge his sincere apprecia-

tion to Dr. S. L. Poe, research advisor and chairman, for

his patience and assistance throughout the course of this

study. Special appreciation is extended to the supervisory

committee, Drs. J. W. Jones, C. A. Musgrave, D. H. Habeck,

and C. S. Barfield for advice and critical reviews of the

dissertation

.

The author wishes to express his gratitude to the

Department of Entomology and Nematology and in particular

to Stephanie Burgess, Gail Childs, Micky Ilartnett, Donna

Labella, Mike Linker, Carol Lippicott, John O'Bannon, Randy

Stoutt, and John Wood for help with field work.

The author also wishes to thank Dr. Habeck for identif

cation of lepidopterous larvae, Skip (Paul) Choate for

identification of Caribidae, and Roger Hetzman for identifi

cation of Geometridae.

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ii

LIST OF TABLES ^

LIST OF FIGURES •

ABSTRACT '^iii

INTRODUCTION 1

LITERATURE REVIEW 5

Foliage Consuming Lepidopterous Pests 5

Predaceous Arthropods Associated with Peanuts ... 9

Spatial Distributions of Arthropods 9

Effects of Defoliation on Plant Growth and yield. .H

SEASONAL DYNAMICS OF DEFOLIATING LEPIDOPTEROUS LARVAE'

IN NORTH CENTRAL FLORIDA PEANUTS 1976-1978 21

Introduction 21

Materials and Methods 22

Results and Discussion 23

SEASONAL DYNAMICS OF PREDACEOUS ARTHROPODS IN NORTHCENTRAL FLORIDA PEANUTS 1976-1978 56

Introduction 56



SPATIAL DISTRIBUTION OF DEFOLIATING LEPIDOPTEROUSLARVAE ON PEANUTS 72

Introduction 72



EFFECTS OF UNIFORM HAND DEFOLIATION OF PEANUTS ONPLANT GROWTH 78

Introduction 78

Materials and MethodsResults and Discussion

iii

APPENDIX

LITERATURE CITED

BIOGRAPHICAL SKETCH

LIST OF TABLES

Table

1. Characteristics of peanut fields used in

survey, Alachua County, Florida , 1976-1978 30

2. Relative abundance of lepidopterous larvaeassociated with Alachua County, Florida,'Florunner' peanuts 1976-1978 31

3. Relative abundance of predaceous arthropodsassociated with Alachua County, Florida,•Florunner' peanuts 1976-1978 66

4. Correlation coefficients between lepidopterousfoliage feeding larvae and predaceous arthro-pods on Alachua County 'Florunner' peanuts 67

5. Percentage fit of counts of foliage consuminglepidopterous larvae to expected frequencydistributions, 1976-1978 76

6. Average percent light interception of intactand defoliated 'Florunner' peanut canopiesafter defoliation .

88

7. Regression equations of pod and crop weightsof intact and defoliated 'Florunner' peanutcanopies ^9

8. Specific leaf weight (SLW) of peanut leavesfrom intact and defoliated 'Florunner'peanut canopies in relation to weeks afterplanting 90

9. Effect of defoliation of 8 week-old 'Florunner'peanut plants on plant parts, 2 weeks post-treatment 91

10. Effect of defoliation of 'Florunner' peanutplants on plant parts at 19 weeks 92

11. Dry weight of leaves from intact and defoliated'Florunner' peanut plants 2 weeks after defol-iation 93

12. Solar radiation, temperature, rainfall andirrigation during growing season, 1978 98

V

LIST OF FIGURES

Figure Page

1. Location of Alachua County , Florida, peanutfields sampled in survey of peanut arthropods,1976-1978 33

2. Mean' numbers of FAW , CEW , and VBC larvaesampled from Alachua County, Florida, peanuts1976-1978. Breaks in lines indicate datesof insecticide application

3. Mean numbers of FAW larvae sampled fromAlachua County, Florida, 'Florunner' peanuts,1976-1978

4. Mean numbers of CEW larvae sampled fromAlachua County, Florida, ' Florunner ' peanuts,1976-1978 45

5. Mean numbers of VBC larvae sampled from

Alachua County, Florida, ' Florunner ' peanuts,1976-1978. .

". 47

6. Mean numbers of VBC, FAW. and CEW larvaesampled from various age of Alachua County,Florida, 'Florunner' peanuts, 1976-1978

7. Mean numbers of Plusiinae looper larvaesampled from Alachua County, Florida, 'Florunner'peanuts, 1976-1978

8. Mean numbers of GCW larvae sampled from AlachuaCounty, Florida, 'Florunner' peanuts, 1976-1978. ... 53

9. Mean numbers of BAW larvae sampled from AlachuaCounty, Florida, 'Florunner' peanuts, 1976-1978. ... 55

10. Mean numbers of ants, spiders, and L. ripariasampled from Alachua County, Florida, 'Florunner'peanuts, 1976-1978 69

11. Mean numbers of Geocor is spp., nabids, and 0.

insidiosus adults sampled from Alachua County,Florida, 'Florunner' peanuts, 1976-1978 71

vi

Figure Page

12. Quadratic regression of percent light inter-ception to LAI of defoliated and intact peanutcanopies, ** significant at 'v =0.01 level,and * significant at rT=0.05 level 95

13. Dry matter accumulation in peanut plant partsin relation to weeks after defoliation. Podweight is adjusted by factor of 1.88 X kernelweight 97

vii

Abstract of Dissertation Presented to the Graduate Councilof the University of Florida in Partial Fulfillment of the

Requirements for the Degree of Doctor of Philosophy

SEASONAL ABUNDANCE OF DEFOLIATING LEPIDOPTEROUS LARVAE ANDPREDACEOUS ARTHROPODS AND SIMULATED

DEFOLIATION DAMAGE TO PEANUTS

By

John Robert Mangold

December, 1979

Chairman: Sidney L. PoeMajor Department: Entomology and Nematology

A survey of lepidopterous larvae on north central Florida

peanuts detected 27 species during 1976-1978. The most abun-

dant larvae were velvetbean caterpillar, Ant icarsia gemmatalis

(Hubner), fall armyworm, Spodoptera f rugiperda (J. E. Smith),

corn earworm, Heliothis zea (Boddie), Plusiinae loopers,

granulate cutworm, Felt ia subterranea (Fabricius) , and beet

armyworm Spodoptera exigua (Hubner). Only the former 3 species

of larvae reached damaging levels.

Fall armyworm larvae were most abundant during mid-July

to early August when peanuts were 12-17 weeks old. Corn ear-

worm larvae were most numerous in mid-July when peanuts were

ca. 12 weeks old. During August through early October velvet-

bean caterpillar larvae were most abundant on peanuts 15-17

weeks old.

The most abundant and important predators surveyed

in peanuts were ants, spiders, Labidura r ipar ia (Pallas),

viii

Geocoris spp. nabids, Orius insidiosus , and ground beetles.

Ants were abundant and probably important predators through-

out the season. Spiders were common predators for the entire

season. Labidura riparia numbers increased rapidly during the

season to greatest numbers at the season's end. Geocoris spp.

and nabids were abundant from mid-August to September then

declined in number late in the season. Peak abundance of

0. insidiosus occurred during mid-June and early July, then

declined sharply.

Correlation coefficients between predators and foliage

feeding larvae indicated nabid abundance was closely associ-

ated with velvetbean caterpillar numbers. Spiders, L. riparia,

Geocoris spp. and 0. insidiosus were also associated with

larval numbers.

The spatial distributions of fall armyworm, corn earworm,

velvetbean caterpillar, Plusiinae loopers, and granulate cut-

worm were fit to 6 frequency distribution models. The common

k values calculated for the 5 species were 3.93, 5.20, 7.27,

2.57, and 3.58 respectively. Only the first 2 common k

2values significantly fit (P==0.05) a test for homogenity

of k.

Uniform hand defoliation of peanut canopies at 4 levels

reduced yield of peanuts. Increases in specific leaf weight

and decreases in light interception of defoliated canopies

were recorded. Quadratic regressions of light interception

as a function of leaf area index were calculated for defoli-

atai and intact canopies. Plants defoliated 75% at 8 and 11

weeks after planting compensated for defoliation by growing

ix

significantly more leaves than undefoliated plants. Plants

defoliated 75% at 8 weeks also decreased stem growth. De-

foliation also reduced crop and pod growth rates of defoli-

ated plants compared to undefoliated plants.

X

INTRODUCTION

The increasing world population has focused our atten-

tion on high protein food plants among which is Arachis

hypogea L., the groundnut or peanut. Leading producers of

peanuts by acreage are: India 35%, China 15%, United States

8%, Nigeria 8%, and Senegal 7% (Janick et al . 1974).

Approximately 650,000 ha of peanuts are produced annually

in the United States. Peanuts rank ninth in acreage among

major field crops and second in dollar value per acre in

the United States (McGill et al . 1974). The distribution

of peanut acreage allotments in the United States is:

Georgia 33%, Texas 23%, Alabama 14%, North Carolina 11%,

Oklahoma 9%, Virginia 7%, Florida 4%, and South Carolina 1%

(McGill et al. 1974).

Peanuts are one of many crops in Florida's diversified

agriculture. The Florida peanut acreage is ca. 22,270 ha

of which 3,080 ha are in the state's north central peanut

growing belt centered in Alachua, Levy, and Marion Counties

(USDA 1977).

Most insecticide applications on peanuts in the south-

eastern United States are made to control foliage consuming

lepidopterous larvae (French 1973). Pilot pest management

programs have demonstrated that insecticide usage can be

1

2

substantially reduced with weekly population assessment and

economic thresholds as a guideline for insecticide applica-

tion (French 1975), The economic thresholds currently in

use are based on limited data from defoliation experiments,

larval consumption data, and principally on experience.

Among the first steps toward the implementation of a

pest management program are the determination of the insect

pest species present in peanut fields and the evaluation of

their effect upon the crop. In the United States the peanut

pest complex varies with locality necessitating regional

surveys. A knowledge of the regular, occasional, and poten-

tial pests in a particular area is necessary before steps

can be taken to control them with timely usage of insecti-

cide .

The seasonal dynamics of defoliating 1 epidopterous

insects on peanuts in Florida has not been documented.

Seasonal occurrence information for populations described

in the literature from other states is based primarily on

experience and not on long term studies. Data relating

plant age to numbers of foliage feeding larvae have not been

published, but are necessary for determining which plant

ages should be critically studied in relation to defoliation.

Foliage consuming larvae considered important in the

southeastern United States include fall armyworm, Spodoptera

f rugiperda (J. E. Smith), corn earworm, Hel iothis zea Boddie,

velvetbean caterpillar, Anticarsia gemmatalis Hubner, granu-

late cutworm. Felt i.-3 subterranea (Fabricius), and beet army-

worm, Spodoptera exigua (Ilubner) (Bass and Arant 1973).

3

The use of natural control agents such as predators and

parasites is ideally maximized in a pest management program.

The parasite complex of lepidopterous larvae on Florida

peanuts has previously been discussed (Nickle 1977) however,

no description of the predaceous arthropod complex on peanuts

in the southeastern United States has been reported. Any

understanding of the biotic potential of both major and

minor pests is impossible without an analysis of the predator

complex in the crop.

Better quantification of the relationship of defoliation

to yield loss is needed to further define defoliation levels

at which treatments are needed. A systems approach to peanut

plant growth and development as affected by defoliation is

being pursued to develop models that can realistically simu-

late the dynamic nature of insect defoliation and plant

growth (Barfield and Jones 1979). Most previous defoliation

experiments have emphasized defoliation effects on final

yields, but ignored how defoliation caused the observed

effect. Confounding environmental effects such as drought

stress and the presence of other pests such as Cercospora

leafspot have often made defoliation experiments less

meaningful

.

The objectives of the research reported here were to:

1. describe the seasonal occurrence of foliageconsuming lepidopterous larvae on peanuts in

north central Florida

2. determine the seasonal occurrence of predaceousarthropods in north central Florida peanuts

4

3. determine the spatialfeeding lepidopterous

4. examine the effect ofdamage on peanuts usi

distribution of foliagelarvae on Florida peanuts

simulated defoliatorg plant growth analysis

LITERATURE REVIEW

Foliage Consuming Lepidopterous Pests

The arthropod fauna associated with peanuts in the United

States is composed of endemic and introduced species that

have adapted secondarily to this plant of South American

origin. Thus, as a rule, arthropods infesting peanuts in

North America are not specialized feeders, and their relative

importance as peanut pests often is in inverse correlation

to the availability of alternate preferred hosts.

The peanut plant is damaged by a variety of arthropod

pests in the United States. In the southeastern peanut belt

most insecticide applications are made to control foliage

feeding lepidopterous larvae (French 1973). Typically insec-

ticides are applied 0-4 times per field to kill foliage

feeding larvae. Foliage feeding larvae of major economic

significance in the Southeast include fall armyworm,

Spodoptera f rugiperda (J. E. Smith), corn earworm, Heliothis

zea (Boddie), velvetbean caterpillar, Anticarsia gemmatalis

(Hubner), and granulate cutworm, Feltia subterranea (Fabricius)

Other arthropods of major economic importance in Florida

include lesser cornstalk borer, Elasmopalpus lignosellus

(Zeller) and spider mites.

6

The fall armyworm is a periodic defoliator of peanuts

in the southeast. Some feeding damage occurs every year

and frequently sufficient number of larvae are present

to completely defoliate plants in outbreak years (Bass and

Arant 1973). Consequently, severe damage to peanuts in

southeastern Alabama and southwestern Georgia has been

reported (Arant 1948a). In Oklahoma, fall armyworm was

reported numerous in some areas on peanuts during October,

but damaging populations were not common in 1972-1974

(Wall and Berberet 1975).

The corn earworm usually causes light to moderate

damage. Occasionally severe infestations occur and complete

defoliation of plants occurs (Bass and Arant 1973). In a

2 year study in Georgia, Leuck et al . (1967) found indices

of foliage ragging by corn earworm damage were negatively

correlated with yield. Morgan (1979) reported corn earworms

were most damaging during early August in Georgia. Wall and

Berberet (1975) found corn earworm was one of the 2 most

common foliage feeders collected in Oklahoma. The corn

earworm is the most common insect defoliator on peanuts in

the West Cross Timbers area of Texas although populations

usually are not economically damaging (Sears and Smith 1975).

The velvetbean caterpillar also causes damage to

peanuts every year in Alabama, Florida, and Georgia (Bass

and Arant 1973). Damaging populations of velvetbean cater-

pillars are not common in Oklahoma although larvae may become

numerous in October (Wall and Berberet 1975). Velvetbean

7

caterpillar is one of the few peanut defoliators that have

been experimentally proven to significantly reduce yields.

English (1946) applied insecticides for velvetbean cater-

pillar populations in Alabama and reported 9-65% yield

reductions in untreated plots. Arant (1948b) demonstrated

that velvetbean caterpillar defoliation caused 20-43% yield

losses from untreated Alabama peanuts.

The granulate cutworm damages peanuts by feeding on

foliage and underground parts. When infestations are severe,

portions of leaves and stems may bo cut from the plants.

In Georgia damaging infestations may occur from late June

until early August, but are most frequent about mid July

when as many as 11 larvae per row foot may be present (Morgan

and French 1971). Three generations of granulate cutworm

on peanuts have been recorded from Georgia (Bass and Johnson

1978). Cutworm populations peak in late June, late July,

and again in late August: the last generation is usually the

most noticeable and damaging.

The beet armyworm, Spodoptera exigua (Hubner) is a

minor foliage feeding pest that infrequently causes damage.

A few instances of serious defoliation have been reported

(Bass and Arant 1973).

Larvae of the rednecked peanutworm, Stegasta bosqueel 1 a

(Chambers) may cause minor damage (Bass and Arant 1973).

Feeding is confined to unopened leaves and the meristematic

region of buds and thus larvae may retard terminal growth

(Arthur et al. 1959). The rednecked peanutworm is the most

8

common insect pest of peanuts in Oklahoma (Wall and Berberet

1979). Walton and Matlock (1959) obtained significantly

higher yields through use of chemical controls for this pest

in Oklahoma, but Arthur et al . (1959) and Bissell (1941)

reported that control of this pest did not increase yields

in Alabama and Georgia, respectively.

A number of other foliage feeding larvae have been

associated with peanuts. These potentially injurious in-

sects include: the tobacco budworm, Hel iothis virescens

(Fabricius); yellowstriped armyworm, Spodoptera ornithogall

i

(Guenee); the saltmarsh caterpillar. Est igmene acrea (Drury);

the yellow wollybear, Pi acris i a virginica (Fabricius); green

clovorworm, Plathypena scabra (Fabricius); cabbage looper,

Trichoplusia n

j

(Hubner); soybean looper, Pseudoplusia

includens (Walker); cotton square borer, Strymon mel inus

(Hubner); Platynota nigrocerri na Walsingham; and Argyrogramma

verucca (Fabricius) (Kimball 1965, Canderday and Arant 1966,

Tietz 1972, Wall and Berberet 1975, Smith and Jackson 1976,

Martin 1976).

There is a paucity of published information on the

seasonal abundance of foliage feeding larvae. Sears and

Smith (1975) developed a partial monthly life table for corn

earworm on Texas peanuts. Greatest larva] numbers occurred

during July. Weekly averages of foliage feeding larvae in

1972 for 4 Georgia peanut fields were reported by French

(1974). Granulate cutworms, corn earworms , and fall armyworms

comprised 77% of the larvae sampled, but seasonal fluctua-

tions for individual species were not given.

9

Predaceous Arthropods Associated with Peanuts

Knowledge of the seasonal and relative abundance of

predaceous arthropods is helpful in defining their role in

regulating pests of peanuts. With the exception of a

report of striped earwigs, Labidura riparis (Pallas)

collected in pitfall traps in Florida peanuts (Travis 1977),

there have been no studies of seasonal incidence or relative

abundance of predators in peanuts. Martin (1976) found

Coleomegilla maculata (De Geer) and Geocoris punctipes (Say)

the most numerous predators in small peanut plots in north

Florida; and spiders were present in low densities.

Predaceous insects most commonly found in Texas peanut

fields are lady bugs, assassin bugs, lace-wings, ground

beetles, predaceous stink bugs, Geocoris spp., Nabis , Orius,

and praying mantids (Smith and Hoelscher 1975). Spiders

were one of the more numerous predators sampled in a study

of the effect of insecticide placement on nontarget organ-

isms in Texas peanuts in 1972-1973 (Smith and Jackson 1976).

Spatial Distributions of Arthropods

The method of sampling for foliage feeding lepidoptera

larvae has been manual shaking of plant branches onto a ground

cloth similar to the method of sampling soybeans developed by

Boyer and Dumas (1963). The foliage shaking sample method has

been used extensively in Georgia, Florida, Alabama, and Texas

and economic thresholds are based on sampling results obtained

with it. In North Carolina a standard sweep net is recom-

mended for population estimation (Stinner et al . 1979).

10

Recent emphasis on accurate sampling procedures for

insects in peanuts has revealed the need for better defini-

tion of the spatial distribution of these insects. Also,

knowledge of spatial patterns provides insight into the

biology of the species in question. Data on the spatial dis-

tribution of insects is necessary before development of se-

quential sampling schemes may be effected (Waters 1955).

Spatial distribution models are probability distribu-

tions that relate the frequency of occurrence of an event,

depending on the mean of the measurements and in some cases

on one or more parameters.

The most useful statistical distributions in entomo-

logical research have been the Poisson and negative binomial

(Southwood 1978). The Poisson distribution describes a

random distribution with variance equal to the mean. In

insect sampling the variance most commonly will be larger

than the mean, indicating that the distribution is aggre-

gated or clumped. The most useful distribution describing

a clumped insect population has been the negative binomial.

The versatility of this distribution arises from the fact

that it may arise from at least 5 different models (Waters

and Henson 1959).

The probabilities of a Poisson distribution are given

by- /V X

P = g ^ /-^ x = 0, 1, 2, . . .,

X X'!

where P is the expected proportion in the xth class and

X = 0 , 1 , 2 , . . . is the value of a discrete random variable.

11

The mean and variance of the distribution are equal toyU.

The usual procedure is to make a number of observations and

The negative binomial is defined by 2 parameters, the

mean and a positive exponent k. The distribution is gen-

erally expressed by the expansion of

With increasing randomness, the variance of the distribution

approaches the mean and the Poisson more accurately describes

the distribution.

Effects of Defoliation on Peanut Plant Growth and Yield

Typically, peanuts in Florida are planted from early

April to late May; in exceptional years spring droughts delay

some planting until June. 'Florunner' , released in 1969,

is the most widely grown peanut cultivar in the United States.

Over 80% of the peanuts grown in Florida are 'Florunner'.

Peanuts exhibit an indeterminate growth pattern. The

plant growth of 'Florunner' is prostrate with the typical

sequential branching pattern of Virginia type varieties

—

i.e. alternate pairs of reproductive and vegetative nodes

on laterals and no reproductive nodes on main stems.

'Florunner' peanuts grown under normal conditions in

Florida begin flowering at ca. 30 days after planting; peak

the mean of these, x, provides an estimate of ytLand

(q-p) ^ where k> 0 , p= ,and q= 1 + p.

The expansion of the probability is given by

X = 0,1,2

12

flowering occurs at 60 days. After 80 days flowers are no

longer present (McCloud 1974, McGraw 1977). The seasonal

flowering pattern has a frequency curve similar to a normal

distribution. Pegs begin to appear ca. 7-14 days after

flowering. Generally only 15-307o of the flowers produce

mature pods (Smith 1954). Early pegs generally produce a

higher proportion of fruit than pegs initiated later. Usually

by 56 days after planting the first pegs begin to swell into

pods. Pod number per plant increases steadily until ca. 84

days at which time the pod load stabilizes. By day 70, seeds

begin filling. Pod formation is completed soon after the

full pod load is established and growth thereafter is in the

seed (Duncan et al . 1978). The pegs and pods which fail to

mature remain attached to the plant and are not eliminated

by abscission (Smith 1954).

McGraw (1977) used plant growth analysis to describe

'Florunner' growth as follows: Plant growth followed a

sigmoid curve. The first 7 weeks of vegetative growth was

geometric. All assimilates were used for accumulation of

dry matter into vegetative parts. The largest component in

terms of dry matter during this phase was the leaf component.

There was a linear growth phase which extended from week 7

to week 16. At 10 weeks plant development shifted from

vegetative to reproductive growth and the rate of dry

matter production began to slow since more photosynthate

production was required for seed production than vegetative

matter. Dry matter accumulation in the stem and leaf compon-

ent ceased at about 84 days. The pods filled at a linear

rate until maximum dry weight was reached at day 133.

13

Duncan et al. (1978) calculated the crop growth rate

of 'Florunner' from the same data used by McGraw. Linear

regression of crop dry weights from canopy closure at 55

days until seed growth became significant at 70 days deter-

2mined that the crop growth rate was 21.2g/m /day. This was

assumed to be the period of maximum crop growth rate.

Partitioning was used by Duncan et al. (1978) to

refer to the division of daily assimilate between reproduc-

tive and vegetative plant parts. The partitioning factor

may be calculated by comparing the fruit and vegetative

growth rates. A correction is made for the fruit growth

rate to account for the additional energy expenditure of

seed production. Correction factors developed by Hanson

et al. (1961) and Penning de Vries (1974) are used to

compensate for the higher concentration of oils and proteins

in seeds. Duncan et al . (1978) estimated partitioning by 2

methods for 'Florunner'. From comparison of crop and

corrected fruit growth rates the reproductive partitioning

factor was calculated as 84.7%. The value for the repro-

ductive partitioning factor estimated from simulations of

the PENUTZ model was 72% (Duncan et al. 1978).

Two useful terms often used to describe plant canopies

are leaf area index (LAI) and percent ground cover. Percent

ground cover is the percent of soil surface that is covered

by the crop canopy. The LAI is defined as leaf area per

unit of ground area and does not indicate directly the

amount of solar radiation intercepted by the canopy. Larval

14

consumption rates of leaf tissue can, however, be easily

coupled to LAI. Measurement of percent light interception

and LAI of canopies are both needed for describing the

structure of defoliated and intact canopies. For example, ^Rudd et al. (1979) used the light interception— LAI relation-

ship of soybean. Glycine max L. (Merr.) determined by Shibles

and Weber (1965) to model soybean insect defoliation in a

dynamic model of soybean growth and yield.

McGraw (1977) found that ground cover of peanuts

increased geometrically from 10% at 3 weeks to 100% at 8

weeks after planting and remained 100% until harvest. The

LAI increased from 0.11 at 3 weeks to 1.5 at 7 weeks. At

8 and 10 weeks the LAI had reached 3.6 and 5.6, respc;ct ively

.

After 10 weeks the LAI maintained an average of 5.6 for 5

weeks until Cercospora leaf spot partially defoliated the

canopy

.

There have been several reported defoliation experiments

of various varieties of peanuts with very inconsistent yield

reductions (King et al. 1961, Greene and Gorbet 1973, Enyi

1975, Williams et al . 1976, Campbell unpubl"!", Nickle 1977).

Results generally demonstrate that defoliation at early pod-

fill, 8-12 weeks after planting, causes the most serious

yield losses.

King et al . (1961) simulated defoliator damage by

mechanical removal of leaf canopy from the top 1/3 - 2/3 's

^Dr. W. V. Campbell, professor of entomology, North CarolinaState University, Raleigh.

15

of irrigated and dryland peanuts in Texas. Seventy-five

percent defoliation of 56-day-old plants and 50% defolia-

tion of 75-day-old plants did not affect yields of irrigated

peanuts. Thirty-three percent defoliation did not signifi-

cantly reduce yields of 53- and 94-day-old plants, but

higher defoliation levels did reduce yield of dryland

peanuts

.

A mowing machine was used by Greene and Gorbet (1973)

in a 3 year study to approximate 5 levels of defoliation of

'Florunner' peanuts in Florida. Removal of ca. 33% of leaf

area reduced yields at most growth stages; yield was reduced

more when defoliation was delayed. Yield losses ranged

from 1.8-7.4%, 3.7-32%, 8.6-44% and 34-63% for defoliation

levels of 10-15, 20, 33, and 50%, respectively. Some repro-

ductive branches and pegs were removed at the 507o defolia-

tion level.

Enyi (1975) hand defoliated 'Dodoma' edible peanuts at

2 week intervals at 3 levels in Tanzania. Defoliation levels

of 50 and 100% reduced pod and stem weight, and kernel size.

Greatest yield losses occurred to plants defoliated ca. 1

week after early podding stage. It appeared that defolia-

tion reduced pod number by slowing stem growth which resulted

in a reduction in number of flowering nodes.

Williams ot al. ( 1976) det:ermined growth rates of plant

parts of 'Makulu Red' peanuts in Rhodesia. Defoliation

levels of 50 and 75% were achieved by removal of 2-3 leaflets

per tetraf foliate. Compared to the untreated check, defoliation

16

decrcrsed cro]) growth rate^ 2 weeks after defoliation

by 17-42%. Stem and pod growth rates were also decreased

by defoliation.

Campbell (unpubl.) used hand shears to clip leaves

from unirrigated peanuts in North Carolina. Yield reduc-

tions started with 50% defoliation on 15 July and 15 Septem-

ber, and 20% defoliation on 1 September, and 10% defolia-

tion on 1 and 15 August.

Unirrigated 'Florunner' peanuts were hand defoliated

at 5 levels at 2 locations in north central Florida (Nickle

1977). Yield reductions in both plots were most severe at

63 days after cracking. Yield reductions averaged 2-6.8,

7.2-21.6, 16.8-41.2, and 20-51% from 25, 50, 75, and 100%

defoliation, respectively for the 2 defoliation experiments.

Peanut quality was also reduced by some defoliation treat-

ments .

Too often researchers have studied the effect of defol-

iation only in terms of the final harvest. Growth analysis

is a useful tool in the quantitative analysis of plant

growth. Generally 2 assessments are required to carry out

a simple growth analysis of plants with a closed canopy--

i.e., dry weights of plant material per unit area of ground

and LAI of the canopy (Radford 1967). Knowledge of the time

and rate of dry matter accumulation is vital to understanding

the physiology of any crop and is particularly amenable to

studying the effect of defoliation.

17

Previous defoliation studies have examined only the

effect of defoliation on final yield or limited growth

rate changes caused by defoliation. One of the few papers

reporting canopy characters and photosynthesis of defoliated

peanuts was that of Boote et al . (1980). Defoliation of 75%

of the upper 42% of the canopy leaf area of unirrigated

•Early Bunch' peanuts corresponded to 25% of the total

leaf area and reduced light interception from 95.6 to 74%.

Canopy carbon exchange rate was reduced 35% from 20.2 mg

o ? 14COg/dm /h to 13.1 mg C02/dm7h and uptake of was

reduced by 30%.

Nickle (1977) questioned the relevancy of manual

excision of peanut leaflets in establishing crop damage-

yield relationships, manual leaf removal was thought to be

more stressful than larval defoliation. However, Thomas

et al. (1979) demonstrated good agreement in yield losses

between manual soybean leaflet removal and defoliation by

caged cabbage looper, T. ni .

Removal of a fixed proportion of leaflets per tetra-

fioliate throughout the canopy has a further disadvantage

in that it may not realistically simulate the effect of

insect defoliation in terms of canopy damage site. The

early instars of soybean looper on soybeans are reported

to feed selectively on low-fiber containing leaf tissues of

terminal leaves. The later instar larvae feed on non-terminal

leaves (Kogan and Cope 1974). Similar observations of corn

earworm larval damage to peanuts were reported by Huffman

18

(1974) and Morgan (1979). The last 2 instars of noctuid

larvae consume 80-91% of the total consumed foliage (Snow

and Callahan 1968, Nickle 1977), Most researchers have

assumed terminal bud damage is minor compared to the much

greater potential loss of older foliage.

Surveys of foliage feeding larvae on peanuts in 1976

indicated that peanuts 11-19 weeks old were most often

attacked by defoliators (Mangold et al . 1977). Terminal

damage at this time is probably not of major significance

since the majority of leaf matter is present. Sustained

terminal bud damage to younger plants during the geometric

vegetative growth stage may be an important aspect of

defoliator damage by corn earworm and possibly fall army-

worm .

A systems approach to the effect of defoliation on

peanut growth and yield is being pursued (Barfield and Jones

1979). There are currently 3 peanut plant models. Two of

the models lack appropriate mechanisms for coupling defolia-

tion to peanut growth and development (Duncan 1974, Young

et al. 1979). The third model, by Smith and Kostka (1975)

is based on yield loss and larval consumption rates and is

not general enough for studying the dynamics of insect

defoliation on plant growth.

Based on limited dcT-foliation oxperiments, larval con-

sumption data, and principally on experience, an economic

threshold of 4 or more foliage feeding larvae per row foot

was used in a pilot pest management program in Georgia in

19

1972-1974 (French 1975). In 1974 the Georgia pilot program

reduced applications from an average of 2 per field for

defoliators to an average of 0.05 per field in the program's

114 fields. Sampling 7.6 m of row for defoliators by

shaking the branches and the empirical threshold were respon-

sible for the reduction in insecticide usage (French 1973).

In 1975 the Tri-States Pest Management Project was

initiated on corn, soybeans, and peanuts in Georgia, Alabama,

and Florida. Shake cloths were used to sample 0.91 m sections

of row for defoliators. An action threshold of 4 larvae per

row foot was used before early August but later increased

to 6 larvae per row foot after early August (Linker and

Johnson 1978).

In Texas, field observations and limited research data

indicate 3-5 and 6-8 medium to large larvae per row foot

can be tolerated before yield losses will occur on dryland

and irrigated Spanish peanuts, respectively (Hoelscher 1977).

Economic thresholds for defoliators on peanuts should

be revised. The concept of economic threshold is very use-

ful in the primitive state of the art. The economic threshold

refers to the pest population density at which active control

measures should be initiated to prevent the pest from reach-

ing the economic injury level. The economic injury level

is the lowest number of insects that will cause economic

damage. However, there are many factors that ideally should

determine an economic threshold. Beneficial insects, pest

pathogens, plant growth stage, interacting plant pathogens,

20

market prices, weather conditions, farming practices,

economics of crop production, pest species, etc., influence

the economic threshold. Economic thresholds are useful in

providing a guideline to the farmer as to whether it is

economical to control a pest

.

Defoliation studies indicate that plant age greatly

influences the amount of defoliation that can be tolerated

without yield loss. The static nature of current action

thresholds does not reflect the dynamics of the impact of

defoliation on crop yield. Also, studies on larval consump-

tion rates of peanut leaves demonstrate major differences

in relative amounts of foliage consumed among defoliators

(Snow and Callahan 1968, Nickle 1977, Huffman and Smith

1979). Future action thresholds should consider the balance

of defoliator species involved at the time.

SEASONAL DYNAMICS OF DEFOLIATING LEPIDOPTEROUS LARVAE IN

NORTH CENT-RAL FLORIDA PEANUTS 1976-1978

Introduct ion

In the southeastern United States most insecticide

applications on peanuts have historically been made to

control foliage consuming lepidopterous larvae (French

1973). Foliage feeding larvae reported reducing yields

in the southeastern United States include fall armyworm,

Spodoptera f rugiperda,

(J. E. Smith); corn earworm,

Heliothis zea (Boddie); velvetbean caterpillar, Anticarsia

gemmatalis (Hubner) ; and granulate cutworm, Feltia sub -

terranea (F. ) (Bass and Arant 1973).

Practically no information is published on the seasonal

occurrence of foliage consuming lepidopterous larvae on

peanuts. Sears and Smith (1975) developed a monthly life

table for corn earworm on Texas peanuts. Weekly averages

of foliage feeding larvae for 4 Georgia peanut fields in

1972 were reported by French (1973), however; seasonal

fluctuations of individual pest species were not given.

The seasonal occurrence of foliage feeding lepidopterous

larvae on peanuts in north central Florida was studied in

1976-1978 and the results are reported here.

21

22

Matei'ials and Methods

A total of 14 Alachua County, Florida, growers' fields

planted to 'Florunner' peanuts were surveyed during 1976-1978

for relative densities of lepidopterous larvae (Table 1).

Samples were taken at weekly intervals starting on 6 July,

15 June, and 23 June in 1976, 1977, and 1978, respectively,

and continued until harvest. A total of forty 0.91 m of row

samples were taken at each sample date by the ground cloth

method

.

Samples were taken by folding back the branches and

gently placing a ground cloth 0.91X0.91 m against plant

bases of one side of the row. The peanut canopy was beaten

downward vigorously with forearm and hands 6 to 8 times

over the cloth to dislodge arthropods. Arthropods that were

observed either under the branches while inserting the ground

cloth or on the ground cloth were identified, counted, and

recorded

.

In 1976-1977 samples were taken throughout each field

in a manner similar to that used by commercial scouts.

All areas of the field were sampled in a random manner with

not more than 10% of the samples within ca. 20 m of any

field edge. In 1978 samples were taken along the transects

of an X-shaped pattern which was aligned along the diagonals

of the field. Twenty samples per transect were taken every

tenth row in Field M and every thirteenth row in Field N.

Each week sampling began on a different row.

23

The fields surveyed in this study were all in Alachua

County in the vicinity of Archer, Florida (Fig. 1) on the

southern edge of the southeast peanut belt. Approximately

3,080 ha or 14% of Florida's peanut acreage is in north

central Florida. Vegetation surrounding the study sites

was mainly woods and pasture with limited acreages of field

corn and rarely soybeans.

Some of the fields surveyed were adjacent. The adja-

cent fields sampled were: (1) C and D; K and L; and B, I,

and J. Also Field E was located less than 1 km from I and J.

Results and Discussion

The following 27 species of lepidopterous larvae were

associated with Alachua County peanuts: Arctiidae: Dia-

crisia virginica (Fabricius) and Estigmene acrea (Drury)

;

Gelechiidae: Stegasta bosqueela ; Geometridae: Anavitrinella

pampinaria Guenee and Cyclophora serrulata (Packard)

;

Lycaenidae: Strymon melinus (Hubner); Noctuidae: Anicla

infecta (Ochsenheimer ) , Anticarsia gemmatalis ,Argyrogramma

verruca (Fabricius), Elaphria nucicolora (Guenee) Elaphria

grata Hubner, Feltia subterranea , Hel iothis virescens

(Fabricius), H. zea. Pseudaletia unipuncta (Haworth),

Pseudoplusia includens (Walker), Spodoptera eridania (Cramer),

S. exigua, S. dol ichos (Fabricius), S. f rugiperda , S.

latifascia (Walker), S. ornithogalli (Guenee), and Tricho -

plusia ni (Hubner); Pyralidae: Elasmopalpus lignosellus

(Zeller); Pieridae: Eurema lisa (Boisduval and Leconte); and

Tortricidae: Platynota f lavedana Clemens and Sparganothis

24

sulfureana (Clemens). The total numbers of less numerous

lepidopterous species were: 53 E. lignosellus , 15 E. acrea,

8 S. melinus , 6 S. bosqueela , 6 E. nucicolora , 5 A. pampinaria ,

4 E. grata , 3 A. infecta, 3 P. unipuncta , 3 E. lisa , 2 P.

f lavedana , 2 P. virginica , and 1 C. serrulata . S. sulfureana

larvae were collected only from buds and were not observed

in beat cloth samples.

Twelve of the 27 lepidoptera larvae associated with

peanuts are new records: A. infecta , A. pampinaria,

C. serrulata , E. lisa , E. grata , E. nucicolora , P. f lavedana,

P. unipuncta , S. sulfureana , S. dolichos , S. eridania , and

S. ornithogalli . With the exception of P. unipuncta , A.

infecta, and E. grata some larvae of the other 9 species

were reared to adults on peanut foliage.

Every year the 3 most abundant lepidopterous larvae

were velvetbean caterpillar, corn earworm, and fall armyworm

(Table 2). Plusiinae loopers were common in 1976 and 1978,

but not in 1977. Beet armyworm was more numerous in 1977

than in other years. Beet armyworms were also extremely

numerous on soybean seedlings in 1977 in Florida (Anon.

1977a, Anon. 1977b).

Population levels of fall armyworm (FAW) were highest,

reaching 17 per sample in Field H on 4 August, during mid -

July to early August in 1976 (Fig. 2). Field H was the only

field where FAW larvae were the major pest that required

treatment. In the other fields surveyed in 1976, fall army-

worm larvae peaked at 0.5-3.8 larvae per sample with the

25

exception of Fields C and D where 9 larvae per sample were

present the first week of August (Fig. 2). In 1977 larvae

began to be abundant in mid-June in Field K and reached

highest levels in Fields K and L in mid-July (Fig. 2). The

early June abundance of FAW larvae on peanuts in Field K

is probably an indication of the outbreak of FAW reported

throughout the Southeast in 1977. In 1978 population levels

of FAW were low, peaking at 0.6 larvae per sample and 3.1

larvae per sample on 20 July in Field M and Field N, respec-

tively .

Larvae of FAW were less numerous in 1978 than in 1976

and 1977 (Fig. 3). In fields not treated with insecticides

during July a natural decline of FAW larvae occurred during

early to mid-August. In no instances were FAW larvae

numerous after mid-August.

Rearing of Ileliothis spp. larvae on artificial diet

indicated ca. 95% of the Ileliothis in 1976-1977 were H. zea

(Nickle and Mangold, unpubl.). In 1976 the greatest numbers

of corn earworm (CEW) , 8.4 per sample, occurred in Field F

on 21 July (Fig. 3). The range of maximum densities in

other fields surveyed in 1976 was 0.6-4.6 per sample. In

1977 CEW attained very high levels of 19 per sample on 20

July in Field L (Fig. 3). The late planted Field L was

probably an exceptionally attractive oviposition site for

CEW moths because peak flowering occurred during early July

at a time when moths were emerging from field corn. Corn

earworm has demonstrated a preference for the flowering

26

stage of 4 of its major agricultural hosts in North Carolina

(Johnson et al . 1975). In 1978 CEW densities reached their

highest levels of 0.6 and 3.1 in mid-July in Fields M and

N, respectively.

The patterns of seasonal abundance of CEW for 1976-

1978 were very similar (Fig. 4). In all 3 years CEW larvae

were most numerous the third week of July. In fields not

treated with insecticides during July, a natural decline of

larvae occurred during late July. Corn earworm larvae were

never numerous after mid-August.

Velvetbean caterpillar (VBC) larvae were first detected

in peanut fields the second week of July. Velvetbean

caterpillar was the only pest that demonstrated resurgence

after insecticide application (Fields B, G, H, Fig. 2).

The dynamics of VBC resurgence appear very similar to the

resurgence of the same species observed on soybeans (Shepard

et al. 1977). In 1976 VBC larvae were most numerous in Field

G where 36 larvae per sample were counted on 8 September.

Very low numbers of larvae were present in the fields

planted early in April; maximum VBC densities ranged from

0.05-0.60 larvae per sample. Maximum larval densities

ranged from 0.7 to 7.1 per sample in Fields K and L,

respectively in 1977. Highest levels of VBC larvae in 1978

were 8.0 and 2.3 per sample in Fields M and N, respectively.

In 1977 VBC larvae increased in number ca. 2 weeks

later than in 1976 and 1978 (Fig. 5). In no instances were

27

VBC larvae present in numbers greater than 1 per sample

until August. Velvetbean caterpillar larvae were the only

numerous insect pest from mid-August through early October.

Adjacent fields of similar planting dates had similar

patterns of larval abundance in terms of timing and density

—

i.e. Fields C and D; and E, I and J. In the 2 cases where

planting dates of adjacent fields differed 4-5 weeks,

later planted fields had higher larval densities. The late

planted Field B, adjacent to Fields I and J, had 5 times

more velvetbean caterpillar the third week of August.

Similarly, the very late planted Field L had 8 times more

velvetbean caterpillar than the adjacent Field K on 2

September. Also corn earworm numbers were 4 times greater

in Field L than Field K on 20 July. Therefore, planting early

in north central Florida appears to greatly increase the

probability of escape from velvetbean caterpillar problems.

Peak numbers of ovipositing adults are probably missed by

planting early. Also the older plants may be less attractive

as oviposition sites than younger plants.

There were differences in the average numbers of VBC,

FAW, and CEW larvae sampled from various age classes of

peanuts 1976-1978 (Fig. 6); Field L was not included

because of its atypical planting date. Larvae of VBC were

most numerous in peanuts 15-17 weeks old. Larvae o^ FAW

fluctuated in abundance, but in general were abundant in

peanuts 12-18 weeks old. Larvae of CEW were most abundant

in 12 week old peanuts, which is ca. 1-2 weeks after peak

28

flowering. These data indicate that VBC and FAW larval

abundance is probably more related to sample date rather

than plant age. Corn earworm larval abundance appears to

be more equally related to both sample date and plant age,

perhaps because CEW prefers to oviposit in flowering fields.

Plusiinae loopers were most numerous from mid-July

through August (Fig. 7). Highest densities of loopers were

reached in Field D where 2.3 loopers per sample were present

on 18 July. Loopers were the most numerous larvae in Field E.

Granulate cutworm (GCW) larvae demonstrated no clear

seasonal trend between years (Fig. 8). In 1977 and 1978

GCW larvae were most abundant in June while in 1976 GCW

larvae were most numerous from late July to early August.

The lack of clear seasonal fluctuation may be due to the

sampling method. Granulate cutworm commonly spend daylight

hours buried in the soil and thus are best sampled between

12:00 AM and 5:00 AM (Eden et al. 1964).

Numbers of beet armyworms (BAW) peaked at different

times of the season for the 3 years the survey was conducted

(Fig. 9). In 1976 BAW larvae were most numerous during

late July while in 1977 and 1978 larvae were most numerous

in mid-June and early July, respectively. Beet armyworms

were never more numerous than 0.7 per sample during this

study

.

There were no distinct generations of foliage feeding

larvae on north central Florida peanuts detected in this study.

Previously 2-3 generations of velvetbean on soybeans were

29

detected by Menke and Greene (1976) and Strayer (1973).

For most species, except for VBC , larvae gradually increased

over G-7 weeks, peaked, and then gradually declined over 2-3

weeks. Larvae of VBC in early planted peanuts remained at

low numbers throughout the season. In late planted fields

VBC larvae were present for 5 weeks or more before a sharp

increase in numbers occurred. Decline of VBC except for

insecticide intervention on late planted fields was very

slight

.

The larval development periods of FAW, CEW , and VBC

on peanuts are relatively long compared to that of other

plant hosts (Huffman and Smith 1979, Nickle 1977). The

duration of the larval stage is generally 20-30 days on

peanuts compared to 12-25 days on other hosts. Parasitism

of larvae of fall armyworm and corn earworm is 20-60%

(Nickle 1977). Predation further reduces survivors. It is

possible that peanuts act as a trap crop or a sink for

these pests--i.e. few eggs laid by moths survive to the

adult stage.

30

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31

Table 2. Relative abundance of lepidopterous larvaeassociated with Alachua County^ Florida^'Florunner' peanuts, 1976-1978.

„ . % of total larvae sampledSpecies

1976 1977 1978

Anticarsia gemmatalis 38., 7 24 .,4 52. 2

Feltia subterranea 6., 1 4 ., 0 3.0

Ileliothis spp. 14., 8 42,,6 20. 5

Plusiinae loopers 10,. 7 0,.6 7.3

Spodoptera frugiperda 25,, 7 22,,4 13.3

Spodoptera exigua 1..6 5,,0 0.4

Other Spodoptera spp. 1,, 5 0,, 7 1.7

Other 0,. 9 0., 3 1.7

"'"Total number larvae sampled 1976, 1977, and 1978 were 15,6613,403, and 1,982, respectively.

Figure 1. Location of Alachua County, Florida, peanut fieldssampled in survey of peanut arthropods, 1976-1978.

Figure 2. Mean numbers of FAW, CEW, and VBC larvae sampledfrom Alachua County Florida peanuts 1976-1978.Breaks in lines indicate dates of insecticideapplicat ion

.

12

10

8

6

4

2

0

I 2

10

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6

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2

0

9 6

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0 0

8 8

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4 0

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35

Field A1976

FAW—CEWVBC

Field B1976

FAWCEWVBC

Field C1976

-FAW-CFW•VBC

I\

/ \

/ \

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Field D1976

FAWCFWVBC

/1

1

JUNE JULY AUG SEPT

gure 2. Continued.

37

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Field F19/6

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Field G1976

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Figure 2, Continued.

39

LlI

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FIELD J

1976

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FIELD K1977

FAWCEWVBC

FIELD L1977

--FAWCEWVBC

JUNt JULY AUG StF'T

gure 2. Continued.

Figure 3. Mean numbers of FAW larvae sampled from AlachuaCounty, Florida, 'Florunner' peanuts, 1976-1978.

Figure 4, Mean numbers of CEW larvae sampled from AlachuaCounty, Florida, ' Florunner ' peanuts, 1976-1978.

Figure 5. Mean numbers of VBC larvae sampled from AlachuaCounty^ Florida^ 'Florunner' peanuts, 1976-1978.

O

CD

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Figure 7. Mean numbers of Plusiinae looper larvae sampled

from Alachua County, Florida, 'Florunner' peanuts,

1976-1978.

Figure 8. Mean numbers of GCW larvae sampled from AlachuaCounty , Florida, 'Florunner' peanuts, 1976-1978.

Figure 9. Mean numbers of BAW larvae sampled from AlachuaCounty, Florida, 'Florunner' peanuts, 1976-1978.

SEASONAL DYNAMICS OF PREDACEOUS ARTHROPODSIN NORTH CENTRAL FLORIDA PEANUTS 1976-1978

Introduction

Peanuts in Florida are damaged by numerous injurious

insects and mites. The most injurious pests in Florida are

lesser cornstalk borer, Elasmopalpus lignosellus (Zeller),

spider mites, and foliage feeding noctuid larvae. With the

exception of data on Labidura riparia (Pallas) collected

in pitfall traps in Florida peanuts (Travis 1977) there

have been no studies of seasonal incidence of predators.

The importance of predators in inducing mortality of pest

species has been recognized in other row crops with similar

noctuid larval pests such as cotton (Whitcomb and Bell 1964,

van den Bosch and Hagen 1966), and soybeans (Buschman et al

.

1977)

.

There are few reports of incidence of predaceous arthro-

pods in peanuts. Martin (1976) found Coleomegilla maculata

(De Geer) and Geocoris punctipes (Say) to be the most numer-

ous predators, with spiders, and 2 reduviids Zelus cervicalis

Stal, and Sinea spinipes (Herrich-Schaf f er ) present in low

densities in small peanut plots in north Florida. Predaceous

insects most commonly found in Texas peanut fields are lady

bugs, assassin bugs, lace-wings, ground beetles, predaceous

56

57

stink bugs, big-eyed bugs, Nabis , Orius , and praying mantids

(Smith and Hoelscher 1975). The objectives of this research

were to describe the seasonal incidence, species composition,

and relative abundance of predaceous arthropods on peanuts

and make preliminary tests of associations between the most

numerous predator groupings and major noctuid larval pests.

Materials and Methods

A total of 14 Alachua County, Florida, growers ' fields

of 'Florunner' peanuts were surveyed during 1976-1978 for

relative density of predaceous arthropods. The fields are

described in Table 1. Samples were taken at weekly inter-

vals starting on 6 July, 15 June, and 23 June in 1976, 1977,

and 1978 respectively, and continued until harvest. A total

of forty 0.91 m of row samples were taken at each sample

date by the ground cloth method.

Samples were taken by folding back the branches and

gently placing a ground cloth 0.91 X 0.91 m against plant

bases of one side of the row. The peanut canopy was beaten

downward vigorously with forearm and hands 6 to 8 times

over the cloth to dislodge arthropods. Arthropods that

were observed under the branches while inserting the ground

cloth or on the ground cloth were identified, counted, and

recorded

.

In 1976-1977 samples were taken throughout the field in

a manner similar to that used by commercial scouts. All

areas of the field were sampled in a random manner with not

58

more than 10% of the samples within ca. 20 m of field edge.

In 1978 samples were taken along the transects of an X-shaped

pattern which was aligned along the diagonals of the field.

Twenty samples per transect were taken every tenth row in

Field M and every thirteenth row in Field N. Each week

sampling began on a different row.

A test of association between the most abundant predator

groupings and lepidopterous larvae was calculated using

Kendall's tau-b as suggested by Fager (1957). The Kendall's

tau-b statistic is a nonparametric index of order association

which conforms to Kendall's criteria for correlation coeffi-

cient (Kendall and Stuart 1961).


Due to the difficulty of identifying many of the

predaceous species present, certain predators were grouped

either in the field or in this report. The composition

of the predaceous insect fauna varied considerably with

field and year (Table 3). The most numerous predators

sampled were ants, spiders, Geocoris spp., L. riparia,

nabids, and ground beetles (Table 3). This predator complex

comprised 91-99% of the predators sampled.

Ants were often the most numerous predator observed

composing from 13-50% of the total number sampled. In

unsprayed fields ants were generally present in over 75%

of the samples. The most commonly observed ant species

were Solenopsis geminata (Fabricius), Pheidole spp., and

Conomyrma insana (Buckley). Whitcomb et al. (1972)

59

recorded over 60 species of ants from Florida soybeans.

Since the crops are grown in the same area and are host

to similar pests, the ant fauna of peanuts is probably as

complex. Ants were numerous from June through September

(Fig. 10).

Considered as a group, spiders composed 9.9-45%

of the predators sampled (Table 3). In most fields spi-

ders did not exceed 20% of total predators sampled except

for Fields K, M, and N. In 1978 spiders were classified

into 8 categories as follows: 30.4% other spiders; 19%

small spider species and immatures; 15.87o wolf spiders

(Lycosidae); 12.87o jumping spiders (Salticidae) ,7.0%

crab spiders ( Thomisidae ) ; 5.7% striped lynx, Oxyopes

salticus Kent (Oxyopidae) , 5.5% Chiracanthium inclusum

(Hentz) and Aysha gracilis Hentz (Clubionidae and Anyphae-

nidae, respectively); and 3.8% green lynx Peucetia viridans

(Hentz) (Oxyopidae). Spiders were common predators for

the entire season and increased in number slowly during

the season (Fig. 10).

Big-eyed bugs, Geocor is spp., comprised 2.1-16% of the

prfdator complex. In 1977. 17.9% of the Geocoris counted

were G. ulignosus (Say) adults, 5.7% G. ul i gnosus nymphs,

38.6% other Geocoris spp. adults, and 37.8% other Geocoris

spp. nymphs (n=352). In 1978, G. ulignosus adults comprised

24.9% of the total, G. ulignosus nymphs 12.2%, G. punctipes

(Say) adults 19.27o, and 43.7% other Geocoris spp. nymphs,

and no G. bullatus (Say) adults were sampled (n=213).

60

From relatively low numbers at the start of the season,

Geocoris numbers increased gradually, reached a peak of

0.43 per sample, then declined in number during September

(Fig. 11).

The striped earwig, L. riparia ,fluctuated widely in

abundance between fields composing 1.8-47.4% of beneficials

sampled. Most of the L. riparia sampled were observed

while parting the foliage in preparation for beat cloth

placement. Labidura riparia numbers climbed rapidly

from very low initial numbers to greatest numbers of 1.1

per sample at the season's end (Fig. 10). Mark-recapture

analysis of absolute earwig population levels in 2 Alachua

County peanut fields during late August and early September

indicated maximum populations of 34,400-85,227 earwigs/ha

(Travis 1977).

Nabids were relatively abundant only midway through the

season and a decline in nabid numbers occurred in September

(Fig. 11). In 1976 Tropicanibis capsiformis (Germar) and

Reduviol is roseipenn is (Reuter) composed 99 and 1%, respec-

tively, of the total nabids collected for identification

(n=100). Of 240 nabids sampled in 1978, 96% were T. capsi -

formis , 2.5% were R. roseipenn is , and 1.5% were Pagusa

fusca (Stein )

.

Adults of the insidious flower bug, Or ius insidiosus

(Say), reached peak abundance during mid-June and July, then

declined sharply (Fig. 11). Patterns of abundance of 0.

insidiosus may be associated with peanut flowering since

61

pollen seems to be an important part of diet of both nymphs

and adults (Dicke and Jarvis 1962). Also, tobacco thrips

are most abundant before flowering and may serve as prey.

Ground beetle adults and larvae composed 3.2-9.5% of

the predator complex. The most numerous species of ground

beetle were the foliage dwelling Cal 1 ieda decora (Fabricius).

Cal lieda decora comprised 75 and 53% of the carabids sampled

in 1977-1978 respectively, Peak abundance of C. decora

larvae occurred near peak numbers of fall armyworm and corn

earworm. Collurius pennsylvanicus (Linnaeus) adults composed

7.3 and 47% of the carabids collected in 1977 and 1978,

respectively. Other carabids infrequently encountered were

adults of Anisodacty lus merula Germstacker, Selenophorus

palliatus Fabricius, S. ellipticus Dejean and Teragonoderus

intersectus Germar and larvae of Progalerit ina spp. and

Calosoma say

i

Dejean.

Many of other predaceous arthropods occurred in numbers

too low for assessment of their seasonal dynamics. None

of these predators averaged more than 0.5 per sample on a

given date during this 3 year study. Some of the predators

that were observed in most fields in low numbers include:

Doru taen latum (Dohr) ( For f icul idae ) ,Spanogon icus albof as -

ciatus (Reuter) (Miridae) , Zolus cervical is (Stal) (Reduvi-

idae), Sinea spp. (Reduviide), Podisus macul 1 ventrus (Say)

(Pentatomidae ) ,Chrysopa spp. larvae ( Chrysopidae )

,

Scymnus spp. adults ( Coccinel 1 idae ) and Noxtoxus spp. adults

( Anthicidae)

.

62

Classical predator-prey theories predict gross predator

population density fluctuations similar to the host-popula-

tion's gross variations (Watt 1968). Significant positive

correlations demonstrate associations or similar patterns

of variation between larvae and predaceous arthropods.

The explanation for association may be chance, or indicative

of density dependence phenomena.

Spiders were significantly correlated with foliage

feeding larvae (FFL) twice, velvetbean caterpillar (VBC)

6 times, and fall armyworm (FAW) once (Table 4). For

earwigs there were 6 significant associations involving

FFL once and VBC 5 times. Nabids had the greatest total

number of correlations. Nabids were correlated with FFL

4 times, VBC 11 times, and FAW once. Geocoris spp. showed

few correlations; they were associated with VBC twice, FAW

twice, and CEW twice. Ants were associated with VBC once,

the fewest significant associations of all predator group-

ings. Orius insidiosus adults showed significant correla-

tions with FFL twice, FAW 3 times, and CEW 3 times.

For further elucidation of association patterns a

refinement in sampling technique and statistical analysis

is needed. Absolute samples or calibrated relative samples

of pests and beneficials analyzed using multivariate analysis

may prove useful in clarifying associations.

Some inferences about the relative importance of pre-

daceous arthropods on north Florida peanuts can be made.

63

Ants were the most numerous predators sampled and

probably one of the most important predators regulating

pest populations. Ants have been frequently observed con-

suming lepidopterous eggs in Florida soybeans (Buschman et

al . 1977, Nickerson et al . 1977). Lack of many significant

correlations between larvae and ants is not surprising

considering ants were one of the most under-sampled predators

in this study. Some species of ants only forage at night

(Whitcomb et al . 1972) and most ants are underground at any

given time.

Because of the abundance of families represented spiders

occupy a variety of feeding niches. Whitcomb (1974) stated

4 important roles of spiders as follows: (1) spiders prey

on destructive insects; (2) spiders serve as food for pred-

ators; (3) spiders tend to be general feeders, and (4) spi-

ders compete with insect predators for prey. Spiders have

been reported as important egg predators in Florida soybeans

(Buschman et al . 1977). The abundance of spiders in peanuts

suggests they are important in effecting pest population

dynamics

.

Eggs and small larvae of noctuids are part of prey of

Geocoris spp. However Geocoris spp. consume a very broad

array of prey (Crocker 1977). Menke and Greene (1976)

reported large Geocoris spp. populations exerted little

population regulation of velvetbean caterpillar populations

in north Florida soybeans. Consequently, Geocoris spp. were

probably not major predators in north central Florida peanuts.

64

The habits of ground beetles are extremely varied

often within the same genus. Callieda decora was the only

ground beetle sampled in sufficient numbers to be important

in some fields. In 1977 C. decora was observed numerous

times feeding on small to medium corn earworms. Calosoma

sayi adults and larvae were numerous in pitfall traps in

peanut fields with high VBC populations in 1976 (Travis

unpubl.). Calosoma sayi consumes and reacts to noctuid

pests of soybeans by taking progressively more prey items

as they become available (Price and Shepard 1978). Calosoma

sayi is one of the few potentially important predators

of large larvae and pupae in peanuts.

Labidura riparia were important predators in most

fields during this study. Earwigs were especially uncommon

in Field N in 1977; it is possible that application of para-

thion on 6 July followed by a 27 July application of

monocrotophos may have greatly reduced the earwig popula-

tion in this field. All stages of noctuids may be consumed

by L. riparia (Schlinger et al. 1959, Hasse 1971, Neal 1974).

In laboratory tests functional response of earwigs to noctuid

larvae prey indicated that successful attacks increased

with higher host density (Price and Shepard 1978). That

L. riparia. numbers were associated with foliage feeding

larvae was demonstrated by significant correlation coefficients

and the gradual increase in earwig numbers during the season

(Fig. 10). L. riparia is considered an important predator

65

in Florida soybeans (Neal 1974, Buschman et al . 1977).

Labidura riparia is probably one of the most important

predators in peanuts in north central Florida.

T. capsiformis adults and nymphs were potentially

important predators of VBC larvae. The increase in nabid

populations closely followed the increase in VBC larvae.

Nabids were uncommon earlier in the 3 seasons when FAW

and CEW were present. Nabids consume eggs and small larvae

of noctuid pests.

0. insidiosus was not numerous during the season when

defoliators were numerous. However, 0. insidiosus may

have served to suppress early season outbreaks of some

pests during June. During the increase in VBC numbers 0.

insidiosus were not common.

66

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SPATIAL DISTRIBUTIONS OF DEFOLIATINGLEPIDOPTEROUS LARVAE ON PEANUTS

Introduction

Spatial distributions are a useful means of quanti-

fying the dispersion of insects in a given habitat. Spatial

distributions are useful in several ways: (1) to aid in

determining the appropriate transformation for analysis of

variance; (2) to develop sequential decision plans; and

(3) to develop sampling plans. Also, inferences about the

biology of the insect e.g., dispersal patterns, can be

made. Spatial distribution models are probability distri-

butions that relate the frequency of occurrence of an event,

depending on the mean of the measurements and in some cases

on one or more parameters.

The most useful statistical distributions in entomo-

logical research have been the Poisson and negative binomial

(Southwood 1978). The Poisson distribution describes a

random distribution with variance equal to the mean. Most

commonly in insect sampling the variance will be larger

than the mean, indicating that the distribution is aggregated

or clumped. The most useful distribution describing a

clumped insect population has been the negative bionomial.

72

73

The versatility of this distribution arises from the fact

that it may be derived from at least 5 different models

(Waters and Henson 1959).

The objective of this study was to determine the spa-

tial distribution of the major foliage feeding insect pests

of peanuts in Florida.

Methods and Materials

Forty samples per week were taken by the ground-cloth

shake method from 0.91 m of row from growers' fields of

'Florunner' peanuts, 1976-1978. Thus the field counts of

foliage feeders were taken from different field sizes and

population densities.

Insects sampled included velvetbean caterpillars,

Anticarsia gemmatalis Hubner; fall armyworm Spodoptera

f rugiperda (J. E. Smith); corn earworm, Ileliothis zea

(Boddie); granulate cutworm Feltia subterranea (Fabricius);

•and Plusiinae loopers : Trichoplusia ni (Hubner), Pseudo -

plusia includens (Walker), and Argyrogramma verruca,

(Fabricius). Mixed populations of loopers prohibited

differentiation of these species in the field.

Data sets were arranged into discrete frequency classes

and fitted to mathematical distributions utilizing a compu-

ter program developed by Gates and Ethridge (1972). Only

those data sets with 4 or more frequency classes were

analyzed and fitted to a distribution. The observed

74

frequency distribution for the following distributions:

Poisson, Poisson-binomial , Poisson with zeroes, negative

binomial, Neyman type A, and Thomas double Poisson.

The iterative solution technique of Bliss and Fisher

(1953) was used determining the parameter k of the negative

binomial. Common k values were calculated by the iterative

method (Formula 10) of Bliss and Owen (1958).


Data sets of counts of lepidopterous larvae fitted

the negative binomial or Poisson with zeroes better than

any other distribution (Table 5). Data sets obtained from

counts of fall armyworm and velvetbean caterpillar fit

the negative binomial significantly better than Poisson.

The percent fit of data sets to the negative binomial for

all larvae was relatively high— i.e. 82-90% while similar

studies in soybeans by Shepard and Garner (1976) and in

cotton (Kuehl and Fye 1972) showed lower fits of negative

binomial for some of these same species. The Poisson

distributions fit the data fewer instances, 41-70% in every

case

.

Values of common k for larvae were 3.93 for fall army-

worm, 5.20 for corn earworm, 7.27 for velvetbean caterpillar,

2.51 for granulate cutworm, and 3.58 for loopers. Only the

oformer 2 common k values significantly fit (P=0.05) a

test for homogeneity of k in the different samples.

75

The value of k may not be a constant for a population

but often increases with the mean. However, regressions

of 1/k versus population means for individual species were

not significant P=0.05. This indicates that k values and

means were not related. Large variation in sample k values

caused the lack of fit. Neither size or age classes of

larvae were considered in fitting distributions. Grouping

instars may have increased the k values by combining the

different instar distributions.

When action economic thresholds for peanuts are revised

sequential sampling plans may be developed using the formula

presented by Waters (1955). The common k values determined

for fall armyworm and corn earworm can be used for calculat-

ing decision lines. The formula for decision lines for

populations described by the Poisson distribution will be

adequate for the other species of lepidopterous larvae.

76

Table 5. Percentage fit of counts of foliage consuming lepidop-terous larvae to the expected frequency distributions,1976-1978.

Fall Corn^ 3,VelvetbeanRank armyworm % Fit earworm % Fit caterpillar

1 Neg. binomial 84 Poisson /zeroes 84b Neg. binomial

2 Neyman 73b Neg. binomial 82 Neyman

3 Poisson-bin

.

69b Neyman 82b Poisson-bin

.

4 Thomas 66b Poisson-bin

.

77b Poisson/zeros

5 Poisson/zeros 65b Thomas 73b Thomas

6 Poisson 41d Poisson 61b Poisson

Number of observed frequency distributions equals 51 for FAW,44 for Ileliothis spp., 39 for VBC , 33 Cor loopers , and 28 forGCW

% fit not significantly different from the % fit of the nega-tive binomial distribution at the 57o level

% fit significantly different from % fit of negative binomialat 5% level

% fit significantly different from % fit of negative binomialat 1% level

77

Table 5. — Extended

Granulate% Fit Loopers^ % Fit cutworm % Fit

87 Poisson/zeros 94b Neg. binomial 90

80b Neg. binomial 88 Neyman 85b

77b Neyman 82b Thomas 85b

74b Thomas 79b Poisson/zeros 82b

61b Poisson-bin. 73b Poisson-bin. 75b

54c Poisson 70b Poisson 68b

EFFECTS OF UNIFORM HAND DEFOLIATION OFPEANUTS ON PLANT GROWTH

Introduction

Peanut (Arachis hypogaea L.) yields in the southeastern

United States may be reduced by a complex of arthropod

pests. Most of the insecticide applications in the south-

eastern peanut belt are made to control foliage feeding

noctuid larvae (French 1973). Foliage feeding larvae report-

ed capable of causing yield loss include corn earworm,

Heliothis zea (Boddie), fall armyworm, Spodoptera f rugiperda

(J. E. Smith), and velvetbean caterpillar, Anticarsia

gemmatal is (Hubner) (Bass and Arant 1973). In Florida,

noctuid larvae may become numerous 10 weeks after planting

and damaging levels of larvae may occur until harvest.

Information relating peanut foliage loss to yield

is variable for a given plant age and variety. Previous

defoliation experiments have dealt with peanut varieties

other than 'Florunner' (Enyi 1975, Williams et al. 1976,

King et al. 1961) or have examined only the influence of

defoliation of 'Florunner' on yields only (Greene and Gorbet

1973, Nickle 1977).

A mowing machine was used by Greene and Gorbet (1973)

to remove the upper portions of peanut canopies to approx-

imate 5 levels of defoliation of 'Florunner' peanuts in

7S

79

Florida. Removal of an estimated 33% of leaf area reduced

yields 5-44% except for a 2% yield increase at 81-90 days

after planting. Yield reductions averaged for the 3 years

of defoliation experiments at 58, 65, and 108 days after

planting were 3.8, 13, 21.5, and 44% yield loss from 10-15,

20, 33, and 50% defoliation, respectively. At the 507o

defoliation level some stems and pegging branches also

were removed.

Nickle (1977) hand defoliated unirrigated 'Florunner'

peanuts in Florida at 5 dates. Yield reductions averaged

2-6.8, 7.2-21.6, 16.8-41.2, and 20-51% from 25, 50, 75,

and 100%. defoliation respectively for the 2 defoliation

experiments. Greatest yield reductions for both experiments

resulted when defoliation occurred at 63 days after seed-

ling emergence.

Few studies describe how defoliation affects peanut

canopy characteristics and plant growth. Boote et al . (1980)

reported the effect of 75% hand defoliation of the upper

42% of canopy leaf area of unirrigated 'Early Bunch' peanuts.

Measurements were made of light interception, specific

leaf weights (SLW) , leaf area index (LAI), apparent canopy

14carbon exchange, and photosynthet ic uptake of CO^

4 days after defoliation. Effects of defoliation on peanut

growth and yield are being quantified using a modeling

approach (G. Wilkerson"*") . Simulation of peanut defoliation

'"Ms. Gail Wilkerson, graduate assistant, Univ. of Florida.

80

will enable the experimental control of the many interacting

factors (environment, insect populations, crop phenology)

at will. Current peanut plant growth models (Duncan 1974,

Young et al . 1979) lack components for coupling defoliation

to plant growth. Objectives of the present study were to

describe how defoliation affects canopy characteristics

and plant growth.

Materials and Methods

Peanuts cv. 'Florunner' were hand planted in 3 blocks

42m X 22 rows 22-23 May 1978 at the University of Florida

Agronomy Farm, Alachua County, Florida. The soil type was

Arrendondo fine sand. Row spacing was 76.2 cm with plants

spaced 13.8 cm apart in the row, which is within the range

of plant population for maximum yield (Malagamba 1976).

Weed control was achieved with preplant ( . 6 kg a.i./ha

benfluralin and 2.3 kg a.i./ha vernolate) and cracking time

(2.8 kg a.i./ha dinoseb and 2.4 kg a.i./ha 2,4-DEP) herbi-

cides. Ethylene dibromide (253 ml/chisel/lOOm) was injected

5 days before planting for nematode control. Gypsum was

applied by hand at 1700 kg/ha on 26 June. The fungicide

chlorothalonil was applied at 0.8-1.1 kg a.i./ha starting

on 22 June at 7-10 day intervals until 22 September.

Monocrotophos (1.9 kg a.i./ha) was applied on 29 June

for lesser cornstalk borer ( Elasmopalpus lignosellus (Zeller)).

Either methomyl ( . 6 kg a.i./ha), carbaryl (1.2 kg a.i./ha) or

81

acephate (1.1 kg a.i./ha) were used to kill foliage feeding

noctuid larvae (corn earworm, velvetbean caterpillar,

fall armyworm, and Plusiinae loopers) and were applied at

7-14 day intervals from 15 July until 22 September. Insec-

ticides and chlorothalonil were tank mixed and applied with

a pressurized backpack sprayer. On 24 August f ensulfothion-

PCNB granules (40.3 kg a.i./ha and 13.4 kg a.i./ha, respec-

tively) were broadcast by hand to slow the spread of white

mold, Sclerot ium rolfsii Sacc. infestation. Overhead

irrigation was used to prevent extreme water stress. Pes-

ticides and cultural practices used were designed to minimize

pest damage and still be reasonably similar to typical

grower practices.

Four levels of defoliation were obtained by removing

0, 1, 2, or 3 leaflets from all tetraf foliates with a peti-

ole extension, corresponding to 0, 25, 50, and 75% defolia-

tion, respectively. Fifty leaflets from 3 plots of each

defoliation treatment were saved for leaf area determination

with an automatic area meter and drying at 70° C.

Defoliation and check plots were selected for uniformity

at 5 weeks after planting and assigned randomly to treatments.

Defoliation plots were 1.1 m lengths of row with (1) at

least 1.5m between plots in the same row and (2) undefolia-

ted adjacent border rows. Plots were defoliated at 25, 50,

and 75% at 8, 11, 13, and 15 weeks after planting. At 17

weeks the only defoliation level was 75%. In addition.

82

there was (1) a treatment at 8 weeks of 75% defoliation plus

removal of buds for 7 days and (2) a redef oliation treatment

of 75% defoliation at 15 weeks of some plots 75% defoliated

at 11 weeks.

At 2 week intervals, starting 2 weeks after a defolia-

tion, until harvest at 19 weeks after planting, 3 samples

of 75% defoliated plots of 11, 13, 15, and 17 weeks were

removed. At 19 weeks after planting 4 plots of all treat-

ments were harvested for yield. Similarly, undefoliated

plots were removed at 8, 10, 11, 13, 15. 17, and 19 weeks.

Four replicate samples of the 8th week defoliations also

were removed at 10 weeks. One plant from each plot, not

one of the plants bordering undefoliated plants in the row,

was separated into roots, stems, leaves, pod shells, and

kernels for dry weight determination. The remaining plants

in the plots were dried and total plot weights were obtained

by summing plant parts of a plot and remaining plants.

Leaflets from undefoliated plots were separated into leaflets

present at defoliation ("old" leaves) and intact leaves

("new" leaves) expanded since defoliation date. Leaf area

and dry weights were measured from 50 "new" and "old"

leaves. Single plant part percentages and total plot weight

were used to calculate dry weights of plant parts per unit

area

The photosynthetically active radiation (PAR) inter-

cepted by peanut canopies was measured 1-3 days after defol-

iation using a pyranometer (LI-200S)^ in conjunction with

83

a quantum-radiometer-photorneter (LI-185) , and pringing

integrator (LI-550)"'". Photosynthetically active radiation

measurements were taken 1-3 days after defoliation on days

of clear skies between 900-1500 hours EST. A metal track 3

wide with 3 cm sides was inserted perpendicular to the row

between plants. The pyranometer was pulled by its cord

manually along the track at a timed constant rate for 1

minute. An ambient full sun reading above the canopy was

recorded within 1-2 minutes of canopy reading.


The daily rainfall, irrigation, solar radiation,

maximum and minimum temperatures from planting until harvest

are given in Appendix Table 12.

Percent light interception of peanut canopies under

different levels of defoliation at different plant ages

is given in T.ble 6. The LAI for intact canopies was

3.11, 4.52, 5.65, 6.09, 5.53 and 5.45 at 8, 11, 13, 15, 17,

and 19 weeks after planting, respectively. Quadratic

regressions for LAI and percent light interception of

intact canopies and of canopies defoliated 27-75% at 8,

11, 13, 15, and 17 weeks after planting were calculated

(Fig. 12). Two LAI—percent light interception coordi-

nates taken at 6.5 and 9 weeks after planting used in the

''"Lamba Instruments Corporation, Lincoln, NE

.

84

intact canopy regression were taken from an adjacent peanut

experiment (G. Wilkerson unpubl.)-

Differences in canopy structure at a given LAI is a

probable explanation for the difference in regression equa-

tions of light interception—LAI for intact defoliated

canopies. In general, most of the LAI data used to fit the

defoliated canopy curve represent canopies with greater stem

areas and ground cover. Ten of the 13 defoliated canopies

had an LAI less than 3. Of these 10 canopies, 7 were from

plots 11 or more weeks old. Stem growth is almost complete

at 11 weeks and stems intercept 39% of ambient light when

2leaves are removed from full grown plants (Jones et al.

unpubl.). By 11 weeks ground cover was 100%. The stem

light interception plus the possibly more uniform spacing

of leaves on plants exhibiting 100% ground cover compared to

intact canopies with a LAI less than 3 probably caused the

higher light interception readings of defoliated canopies

at a given LAI

.

To estimate the difference in crop and pod growth

rates of intact and 75% defoliated canopies at 11 and 13

weeks after planting, linear regression curves of dry

weights versus plant age were calculated. Since more photo-

synthate is necessary for kernel development than other

plant parts, a result of the higher concentration of oil

and protein in seeds than in other plant parts, an adjust-

J. W. Jones, C. S. Barfield, K. J. Boote, G. H. Smerage,and J. Mangold. Photosynthetic recovery of peanuts todefoliation at various growth stages. MS in review.

85

ment was used. Average values of the correction factors

developed by Hanson et al. (1961) and Penning de Vries

(1974) for seeds--i.e. 1.88 X kernel weight were used.

The growth response of intact plants, 75% defoliation

at 11 weeks, and 75% defoliation of plants at 13 weeks is

illustrated in Fig. 13. Regression equations for crop

and pod growth rates are presented in Table 7. The crop

growth rate of intact canopies appeared to slow late in

season. The decrease in growth rate was probably due to

the few new leaves that are added and the photosynthetic

rate of older peanut leaves decreases with age ( Trachtenberg

and McCloud 1976, Henning et al. 1979).

There was a greater relative reduction in pod and crop

growth rate of plants defoliated at 13 weeks than at 11

weeks. For plants defoliated 75% at 11 weeks, crop and pod

growth rates were 71.7 and 76.1%, respectively, that of the

undefoliated . Seventy-five percent defoliation at 13 weeks

reduced crop and pod growth rates by 65.3 and 57.1% that

of the undefoliated plants. A plausible explanation for the

larger reduction in growth rates of 13th week defoliated

plants versus 11th week defoliated plants may be related to

the lower average LAI present of 13th week defoliated

plants during the remainder of the growing season. Plants

defoliated in week 11 added LAI.

Partitioning coefficients were calculated from the crop

and pod growth rates. Partitioning refers to the division

86

of photosynthate between reproductive and vegetative plant

parts. Previously pod partitioning coefficients of undefol-

iated 'Florunner' peanuts has been estimated at 73% by

linear regression of dry weights (McGraw 1977) and 84.7% by

the PENUTZ model (Duncan et al . 1978). The calculated pod

partitioning factors for the undefoliated plots from 11-19

weeks and 13-19 weeks. 75% defoliation at 11 weeks, and

75% defoliation at 13 weeks were 75.1, 80.9, 70.7, and 92.5%

respectively

.

Specific leaf weights of defoliated plants significantly

increased in some cases after defoliation as compared to

undefoliated plants (Tables 8, 9). Most of the increase

in SLW was attributed to the increase in "old" leaf SLW.

Old leaves increased in SLW probably due to less shading.

Decreases in SLW with shading for peanuts (An 1976) and

other legumes such as alfalfa, Medicago sativa L. (Wolf and

Blaser 1972) and soybean, Glycine max (L. ) Merr., (Cooper

and Quails 1967) have been reported.

An increase in SLW may be related to increased photo-

synthetic rates. Bhagsari and Brown (1976) detected a

significant positive correlation between SLW and photo-

synthesis in 1 of 3 experiments involving peanut genotypes.

However, no correlation between SLW and net photosynthesis

of peanut leaves were found by Pallas and Samish (1974).

Defoliation reduced yields at most levels and plant

ages, but significant differences from undefoliated peanuts

87

occurred only with 75% defoliation at 8 weeks plus removal

of buds for 7 days, 757o defoliation at 11 weeks, and multiple

75% defoliations at 11 and 15 weeks (Table 10). Early pod

fill ca. 68-day-old plants has previously been shown as the

plant age most sensitive to defoliation (Nickle 1977)

.

Consumption or damage to terminal buds appeared to be an

important compounding effect to uniform canopy defoliation.

The early instars of corn earworm feed selectively on leaf

tissues of terminal buds (Morgan 1979). Sustained terminal

bud damage may be an important aspect of defoliator damage

by corn earworm and possibly fall armyworm especially

during the vegetative growth stage of peanuts.

Seventy-five percent defoliation and 75% defoliation

plus removal of buds at 8 weeks reduced pod and stem weights

at 10 weeks (Table 11). Decreases in stem weight of

'Dodoma' edible peanuts with defoliation have been reported

previously (Enyi 1975). The weight of leaves grown 2 weeks

after 50 and 75% defoliation also was significantly higher

than undefoliated plants. Defoliated peanut plants compen-

sated for defoliation by growing more leaves and reducing

stem and pod growth.

Plants defoliated 75%. at 11 weeks grew significantly

more leaves than undefoliated plants during the 2 week period

following defoliation (Table 11). No detectable differences

in leaf growth between defoliated and undefoliated plants

were detected in other treatments or time periods after

defoliation

.

88

Table 6. Average percent light interception of intact anddefoliated 'Florunner' peanut canopies afterdef ol iat ion

Percent Percent light interceptiondefoliation Defoliation date (weeks after planting)

8 11 13 15 17 19

Intact 69. 5 90,,6 96.,9 94 . 0 92,,9 95. 5

25 68. 3 83,, 1 91., 2 81. 8

50 57. 5 80., 0 75. 8 77. 2

75 51. 8 63..4 70. 5 50. 7 60.,6

75+buds 45.2

Buds removed for 7 days.

89

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90

Table 8. Specific leaf weight (SLW) of peanut leaves fromintact and defoliated 'Florunner' peanut canopiesin relation to weeks after planting.

Age at 75% SLW (mg/cm)defoliation Leaf weeks after planting

(weeks

)

type 11 13 15 17 19

1^ o n "t" T*o T 3 83 3.83 3 . 86 4 . 03 4.12

11 new 3 . 85 4.19 4 . 62 4 . bo

old 4.12 4.20 4.63 4.76

avg. 4.02 4.26 4 .63 4.72

13 new 3.09 4.78 4. 51

old 4 . 20 5. 00 4.91

avg. 4. 06 4.96 4.80

15 new 4.01 4.12

old 4.15 4 . 90

avg. 4. 10 4.80

17 new 4.39

old 4.51

avg. 4 .49

LSD for new leaves, old leaves, and svg. leaves=0.39, 0.45, and0.47, respectively, P=0.05.

91

in

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92

Table 10. Effect of defoliation of 'Florunner' peanutplants on plant parts at 19 weeks.

Level YieldAge defoliation reduction Pod dry^weight

defoliated % % (g/m )

control 0 • 0 495,. lab

8 25 4 . 02 475 . Oabc

8 50 15. 06 420 . 5abcd

8 75 13. 24 429 . 5abcd

8 75+buds 26. 19 365 .4cd

11 25 6. 48 463 . Oabcd

11 50 18. 54 403 . 3abcd

11 75 29. 50 349 . Od

11 , 15 75 26. 05 366 . led

13 25 30 493 . 5ab

13 50 - 1 . 60 503 . Oa

13 75 23. 64 378 . Ibcd

15 25 6. 00 465 . 3abcd

15 50 10. 30 444 . labcd

15 75 21

.

90 386 . 6abcd

17 75 20. 20 394 . Sabcd

Values in a column followed by same letter are not signif-icantly different (?< 0.05), Duncan's new multiple rangetest

.

93

Table 11. Dry weight of leaves from Intact and defoliated'Florunner' peanut plants 2 weeks after defoliation.

Week of Def oil ationN f^\Ml"i W J. d V o o

1 2Dry weight (g/m )defoliation treatment Week added

11 75% 11-13 40.38a

control 11-13 20.66b

13 75% 13-15 12.06a

control 13-15 16.88a

15 75% 15-17 9 . 03a

control 15-17 -10.60a

17 75% 17-19 4.29a

control 17-19 2.06a

Values in a column, for a given week of defoliation followedby same letter are not significantly different (P<0.05),Duncan's new multiple range test.

+->

d

O *

CD 73

O -

rHl-H 0)

<; >0)

rHOP r-l

OC •

O O•H II

+->

D-••

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X3 -Hh£) C•H hDrH

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95

N0lld33d31NI IHOn lN33d3d

Figure 13. Dry matter accumulation in peanut plant partsin relation to weeks after defoliation. Podweight is adjusted by factor of 1.88 X kernelweight

.

97

1800-

lf>00

MOO

1200

1000UJcr<t 800

O 600-

co400-

crUJ 200-

h-

1400-

crLJ 1200

CL1000-

cr.

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600

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o 800-

600-

400

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CONTROL- TOIAlPOOS— LKAVES— STfM---HOOIS

757o-l I WEEKS

757o-l3 WEEKS

10 I I 13

—I

—

15 17 19

APPENDIX

Table 12. Solar radiation, temperature, rainfall andirrigation during growing season, 1978.

Solarradiation Temperature (°C) Rainfall and

Day (Langleys) Max. Min. irrigation (mm)

23 ivicty 4: y o o .o 21 . i

94 O 1 . I 21 . /

/I Q o o oo 20 . 6 5 .

1

oy o 32

.

oO 20.097 bl4 21

.

r-j

f 16 . 19R ODD r-r

1 18.39Q 31

.

7 18.3OU r\ 32

.

2 20 . 0O 1 o n "739 / 32 . 2 19.4 5 . 8i June ooO 32

.

o8 20 . 09 o ri o392 31

.

1 22 . 2oO 292 30 . 0 21.7 25. 9

277 28

.

3 22 . 2 8 . 8O 368 28

.

3 21 . 1

b 485 31

.

1 22. 2I 540 31

.

1 23 . 3 .5Oo rz r\r\o02 33

.

3 24 .

4

9 425 32. 2 23.9 2.510 449 31

.

7 23.9 14.711 449 31. 7 23.3 .312 461 31

.

1 20.613 576 32. 2 23. 314 456 31

.

1 23.3 7.915 464 28. 3 20.016 519 30. 6 18. 917 619 30. 6 18.918 614 30. 6 17. 819 507 30. 6 22. 220 313 29. 4 22. 221 406 32. 2 21.1 10. 222 447 30. 6 22. 2 1.023 578 32. 8 22. 224 478 34. 4 20. 6 26.925 600 32. 2 22. 826 597 33. 9 22. 227 571 33. 3 23.928 497 35. 0 23. 929 554 35. 0 23. 930 600 35. 0 23.9

98

99

Table 12. Continued.

Solarradiation Temperature ( C) Rainfall and


1 July 624 33. 9 23. 3

2 636 34.4 23.33 638 33.9 25. 0

4 294 28.3 23.9 3.35 430 31.1 23.9 6.46 258 27.8 21. 1 5.37 335 20.0 22.8 8.48 478 31.1 22. 2 1.29 609 31.

1

22.2 3.810 590 33.3 23.311 449 33.3 23 . 3

12 270 30.6 22.2 9.913 370 27.8 22. 3 .8

14 425 30.0 22.815 480 31.1 23.316 103 31.

1

23.3 37.617 392 30.6 22.8 8.418 485 30.0 23.3 10. 1

19 397 30.6 21 . 7 4.320 411 28.9 22. 2 . 3

21 519 32. 2 22. 2 .8

22 533 32.2 23.3 6.623 624 32. 2 23.324 628 32. 2 22.2 .3

25 583 33.9 22.8 2.026 337 30. 6 21. 7 1.327 454 31. 1 22. 8 77.528 220 27.8 23. 3 7,129 330 29.4 22. 8 9. 1

30 411 31.1 23.9 6.631 249 30.6 21.11 August 432 30.6 21.

1

82. 8

2 502 31 . 7 22. 2 11.93 614 31.7 21.14 514 31. 1 22. 2

5 478 30. 6 22.8 2.36 313 31 . 7 22.27 571 33. 3 21.78 311 30.0 23.9 .3

9 633 31.7 21.7 4.610 387 30.6 22.2 . 8

11 280 30. 0 22. 8 12. 2

12 342 31.7 23. 3 2.813 249 28.9 22.8 1.014 380 30. 0 22. 2

15 485 33.3 22. 8 50. 1

100

Table 12. Continued

Solarradiation Temperature ( C) Rainfall and


16 August 387 31.7 22 . 8 . 517 464 32 . 8 21.7 2 . 3

18 576 33 .

9

21.7 2 , 3

19 382 31 . 7 20 . 020 516 33 . 3 23 .

9

21 542 32 . 2 21.122 428 31.7 22 . 223 473 31.1 22 . 224 547 31.7 21.125 456 31.7 20 . 0 12.726 499 32 . 2 21.127 593 33 .

9

22 . 2

28 476 35 . 0 22 . 2

29 571 32 . 2 22 . 2

30 573 32 . 8 22.831 509 32.8 21.7 19 . 1

1 September 466 35 . 0 21.72 413 33 . 3 21.7 1 . 8

3 511 32 . 8 21.74 516 33.3 20 . 05 437 33 .

9

19.46 459 31 . 1 18.37 535 32.2 20 . 08 425 32.8 23 . 3 19 . 1

9 378 32.8 22 . 8

10 217 31.7 20 . 011 487 31 7 18 9

12 499 91 7

13 44Q 39 8 90 n

14 411 9 8 90 fi 1 Q 1

15 416 3 91 1

1 6 41 n o o , o 90 R

1 7 ^9 SO ill . O 9 n n

1 8 T 9 R 9n RZ U . D^ QJL t-/ ^ o o o o . o 1 R 11 O . X

^ o o 10 9i5 <i . ^ 9 n RZU . D 1 Q 1X y . i9 ^ o o u TO 9 9 n ozu . y

Ooo . y 9 A nZU . D^ o OR!Z O X Q 9 9 9 1 1Z J. . 1 1 . b24 385 31.1 21 . 725 435 31 . 7 20. 6 .826 354 30. 0 20.6 12. 727 292 29.4 20.028 378 28. 3 18. 329 170 27. 2 20.630 129 25.6 22. 2 7.91 October 306 28. 9 17.22 456 28. 9 16. 1 12 . 73 485 29.4 19.44 308 29.4 15.6

LITERATURE CITED

v-^n, H. N. 1976. Low light intensity at different stagesof growth as affecting peanut yield components. M.

S. thesis, Univ. Fla. 76 pp.

Anonymous. 1977a. Ln Coop. Plant Pest Rep. 2:510.

Anonymous. 1977b. In Coop. Plant Pest Rep. 2:563.

Arant, F. S. 1948a. Status of velvetbean caterpillarcontrol in Alabama. J. Econ. Entomol. 41:26-30.

Arant. F. S. 1948b. Control of peanut insects. Ann.

Rep. Ala. Expt . Sta. 59:43-4.

Arthur, B. W. , L. L. Ilyche. and R. H. Mount. 1959. Controlof the red-necked peanutworm on peanuts. J. Econ.Entomol. 52:468-70.

Barfield, C. S., and J. W. Jones. 1979. Research needs for

modeling pest management systems involving defoliatorsin agronomic crop systems. Fla. Entomol. 62:98-114,

Bass, M. H. , and F. S. Arant. 1973. Insect pests. Chap-ter XII. Pages 388-428. ^ Peanuts--culture anduses. Amer. Peanut Res. Ed. Assoc. , Inc. 684 pp.

Bass, M. H. , and S. J. Johnson. 1978. Granulate cutworm:evaluation of insecticides for control. Agr. Exp.

Sta. Auburn Univ. Leaflet 95. 3 pp.

Bhagsari, A. S., and R. H. Brown. 1976. Photosynthesisin peanut ( Arachis ) genotypes. Peanut Sci. 3:1-5.

Bissell , T. L. 1941. A micro leaf worm on peanuts. J.

Econ. Entomol. 35:104.

Bliss, C. I., and R. A. Fisher. 1953. Fitting the negativebinomial distribution to biological data. Biometrics9: 176-200.

Bliss, L. I., and A. R. G. Owen. 1958. Negative binomialdistribution with a common K. Biometrika 45:37-58.

101

102

Boote, K. J., J. W. Jones, G. 11. Smerage, C. S. Barfield,

and R. D. Berger. 1980. Photosynthesis of peanutcanopies as affected by leafspot and artificialdefoliation. Agron. J. (in press)'.

Bowes, G. , W. L. Ogren , and R. H. Ilageman. 1972. Light

saturation, photosynthet ic rate, RuDP carboxylase:Activity and specific leaf weight in soybeans grown

under different light intensities. Crop. Sci. 11:

77-9.

Boyer, W. P., and W. A. Dumas. 1963. Soybean insect sur-

vey as used in Arkansas. U. S. Dept. Agric. Coop.

Econ. Insect Report. 13:91-2.

v^uschman, L. L.. W. H. Whitcomb, R. C. Hemenway ,D. L.

Mays, Nguyen Ru , N. C. Leppla, and B. J. Smittle.

1977. Predators of volvetbean caterpillar eggs in

Florida soybeans. Env. Entomol. 6:403-7.

Canerday, T. D. , and F. S. Arant . 1966. The looper com-

plex in Alabama ( Lepidoptera , Plusiinae) . J. Econ.

Entomol. 59:742-3.

Cooper, C. S., and M. Quails. 1967. Morphology and chloro-

phyll content of shade and sun leaves of two legumes.

Crop Sci. 7:672-3.

Crocker, R. L. 1977. Components of the feeding niches of

Geocoris spp. (Ilemiptcra: I.ygaeidae). Ph.D. dis-

sertation. Univ. Fla. Ill pp.

Dicke, F. F., and J. L. Jarvis. 1962. The habits and sea-

sonal abundance of Orius insidiosus (Say) (Hemiptera-Heteroptera: Anthocoridae ) on corn. J. Kans . Entomol.

Soc. 35:339-44.

Duncan, W. G. 1974. PENUTZ , a simulation model for pre-dicting growth, development and yield of a peanutplant. Amer. Peanut Res. Ed. Assoc. Proc. 6:72.

Duncan, W. G. , D. E. McCloud, R. L. McGraw, and K. J.

Boote. 1978. Physiological aspects of peanut yieldimprovement. Crop Sci. 18:1015-20.

Eden, W. G., C. A. Brogden , and M. Sconyers. 1964. Thegranulate cutworm in peanuts and its control. Highl.

Agr. Exp. Sta. Bull. 11:13.

English, L. L. 1946. The velvetbean caterpillar on pea-

nuts: control experiments. J. Econ. Entomol.39: 531-3.

103

Enyi, B. A. C. 1975. Effects of defoliation on growth andyield in groundnut ( Arachi s hypogea ) ,

cowpeas (Vignaunguical ata ) ,

soyabean ( Glycine max ) and green gram(Vigna aurens ) . Ann. Appl . Biol. 79:55-66.

Fager, E. W.groups

.

1957. Determination and analysis of recurrentEcology. 38:586-95.

French, J. C.Georgia.

1973. Insect pest management on peanuts inJ. Amer. Peanut Res. Ed. Assoc. 5:125-7.

French, J. C. 1974,Georgia. Proc,

Peanut insect pest management inAmer. Res. Ed. Assoc. 6:5-7.

French, J. C. 1975,gram. J. Amer,

A pilot insect pest management pro-Peanut Res. Ed. Assoc. 7:62-3.

Gates, C. E., and F. G. Ethridge. 1972. A generalized setof discrete frequency distributions with FORTRANprogram. Math. Geology. 4:1-24.

Greene, G. L. , and D. W. Gorbet . 1973. Peanut yieldsfollowing defoliation to assimilate insect damage.J. Amer. Peanut Res. Educ. Assoc. 5:141-2.

—Hanson, W. D. , R. C. Leffel, and Robert W. Howell. 1961.Genetic analysis of energy production in the soybean.Crop Sci. 1: 121-6.

Hasse, W. L. 1971. Predaceous arthropods of Florida soy-bean fields. M. S. thesis. Univ. Fla. 67 pp.

Henning, R. J., R. II. Brown, and D. A. Ashley. 1979.Effects of leaf position and plant age on photosyn-thesis and translocation. Peanut Sci. 6:49-50.

Hoelscher, C. E. 1977. Managing insects on Texas peanuts.Tex. Agr. Ext. Serv. L-704. 8 pp.

Huffman, F. R. 1974. Consumption of peanut foliage bythe bollworm, Heliothis zea (Boddie) ( Lepidoptera

:

Noctuidae). M. S. thesis, Texas A & M Univ. 40 pp.

Huffman, F. R. , and J. W. Smith, Jr. 1979. Bollworm:peanut foliage consumption and larval development.Env. Entomol. 8:465-7.

Janick, J., R. W. Schery , F. W. Woods, and V. W. Ruttan.1974. Plant Science. W. H. Freeman and Company.San Francisco. 740 pp.

104

Johnson, M. W. , R. E. Stinner, and R. L. Rabb. 1975.Ovipositional response of Ileliothis zea (Boddie)to its major hosts in North Carolina. Env.Entomol. 291-7.

Kendall, M. G. , and A. Stuart. 1961. The advanced theoryof statistics, Vol. 3. Charles Griffin and Company,Ltd. London. 405 pp.

Kimball, C. P. 1965. The Lepidoptera of Florida. Anannotated checklist. Fla. Dept. Agri . & ConsumerServices, Div. Plant Industry, Arthropods of Floridaand Neighboring Land Areas. 363 pp.

King, D. R., J. A. Harding, and B. C. Langley. 1961.Peanut insects in Texas. Tex. Agr. Exp. Sta. MP-550.14 pp.

Kogan, M. , and D. Cope. 1974. Feeding and nutrition of

insects associated with soybeans. 3. Food intake,utilization, and growth in the soybean looper, Pseudo-

plusia includens . Ann. Entomol. Soc. Amer. 67:66-72.

Kuehl, R. 0., and R. E. Fye. 1972. An analysis of thesampling distributions of cotton insects in Arizona.J. Econ. Entomol. 65:857-60.

Leuck, D. B. , R. 0. Hammons , L. W. Morgan, and J. E. Harvey.1967. Insect preference for peanut varieties. J.

Econ. Entomol. 60:1546-9.

Linker, II. M., and F. A. Johnson. 1978. Tri-Statcs pestmanagement project in Florida. Pages 25-9. l_n Proc.Nat. Pest Management Workshop. 220 pp.

Malagamba, J. P. 1976. Plant density relationships in

peanuts ( Arachis hypogaea L.) Ph.D. dissertation.Univ. Fla. 104 pp.

Mangold, J. R., D. A. Nickle, and S. L. Poe. 1977.Populations of pests and their natural enemies in

Florida peanuts. Proc. Amer. Peanut Res. Ed. Assoc.9: 70.

Martin, P. B. 1976. Cabbage looper, soybean looper, andtobacco budworm populations near Quincy , Florida:Seasonal abundance, host preference, and suppressionby natural enemies. Ph.D. dissertation. Univ. Fla.255 pp.

McCloud, D. E. 1974. Growth analysis of high yieldingpeanuts. Soil Crop Sci . Soc. Fla. 33:24-6.

105

McGill, J. F. , R. J. Kenning, J. C. French, and S. S.

Thompson. 1974. Growing peanuts in Georgia. Coop.Ext. Serv. Univ. Ga. Bull. 640. 46 pp.

McGraw, R. L. 1977. Yield dynamics of Florunner peanuts( Arachis hypogaea L.) M. S. thesis, Univ. Fla. 38 pp.

Menke, W. W., and G. L. Greene. 1976. Experimental valida-tion of a pest management mode. Fla. Entomol. 2:135-42.

Morgan, L. W. 1979. Economic thresholds of Heliothisspecies in peanuts. Pages 71-4. In Economic thresholdsand sampling of Heliothis species on cotton, corn, andother host plants. Southern Coop. Ser. Bull. 231.

159 pp.

Morgan, L. W. , and J. C. French. 1971. Granulate cutwormcontrol in peanuts in Georgia. J. Econ. Entomol.64: 937-9.

Neal, T. M. 1974. Predaceous arthropods in the Floridasoybean agroecosystem . M. S. thesis. Univ. Fla.196 pp.

Nickerson, J. C, C. A. Ralph Kay, L. L. Buschman , and W. H.

Whitcomb. 1977. The prosonco of Spissi s t ilus f estivusas a factor affecting egg predation by ants in soybeans.Fla. Entomol. 60:193-9.

Nickle, D. A. 1977. The peanut agroecosystem in centralFlorida: Economic thresholds for defoliating noctuids(Lepidoptera , Noctuidae) ; associated parasites;hyperparasitism of the Apanteles complex ( Hymenoptera

,

Braconidae). Ph.D. dissertation. Univ. Fla. 131 pp.

Pallas, J. E., Jr., and Y. B. Samish. 1974. Photosyntheticresponse of peanut. Crop Sci. 14:478-82.

Pearce, R. B., G. E. Carlson, D. K. Barnes, R. H. Hart, andC. H. Hanson. 1969. Specific leaf weight and photo-synthesis in alfalfa. Crop Sci. 9:423-6.

v-'^enning de Vries, F. W. T. 1974. Substrate utilization andrespiration in relation to growth and maintenance in

higher plants. Neth. J. Agr. Sci. 22:40-4.

Pieters, E., and W. L. Sterling. 1974. Aggregation indicesof cotton arthropods in Texas. Env. Entomol. 3:598-600.

Price, J. F. , and M. Shepard. 1978. Calosoma sayi andRabidura predation on noctuid prey in soybeans andlocomotor activity. Env. Entomol. 7:653-6.

iU6

Radford, P. J. 1967. Growth analysis formulae— their use

and abuse. Crop Sci. 7:171-5.

Rudd, W. G. , W. G. Ruesink, L. 0. Newson , D. C. Ilerzog,

R. L. Jenson, and N. F. Marsolan. 1979. The systems

approach to research and decision-making for soybean

pest control. In New Technology of Pest Control(C. B. Huffaker, Ed.). John Wiley & Sons, Inc. NewYork ( in press)

.

Schlinger, E. I., R. Van den Bosch, and E. J. Dietrick.

1959. Biological notes on the predaceous earwigRabidura riparia (Pallas), a recent immigrant to

California (Dermaptera: Labiduridae ) . J. Econ.

Entomol. 52:247-9.

Sears, D. E., and J. W. Smith, Jr. 1975. A natural mor-

tality table for corn earworm on peanuts. Tex.

Agric. Exp. Sta. Prog. Report. 7 pp.

Shepard, M., and G. R. Garner. 1976. Distribution of

insects in soybean fields. Can, Entomol. 108:767-71,

Shepard, M., G. R. Garner, and S. G. Turnipseed. 1977.

Colonization and resurgence of insect pests of soybean

in response to insecticides and field isolation. Env.

Entomol. 6:501-6.

Shibles, R. M., and C. R. Weber. 1965. Leaf area, solarradiation interception and dry matter production by

soybeans. Crop Sci. 6:55-9.

Smith, B. W. 1954. Arachis hypogaea,reproductive effi-

ciency. Amer. J. Bot . 41:607-16.

Smith. J. W. , and C. E. Hoelscher. 1975. Insect pestsand their control. Pages 68-73. Iji Peanut productionin Texas. Tex. Agric. Exp. Sta. RM 3,

Smith, J. W., and P. W. Jackson. 1976. Effects of insecti-

cidal placement on non-target arthropods in the peanut

ecosystem. Peanut Sci. 3:87-90.

Smith, J. W., Jr., and D. G. Kostka. 1975. Modeling fol-

iage consuming lopidoptera on peanuts. Amer. Peanut

Res. Ed. Assoc. Proc. 7:66,

Snow, J. W. , and P. S. Callahan. 1968. Biological andmorphologica]. studies of the granulate cutworm, Feltiasubterranea (F. ) in Georgia and Louisisna. Ga. Agr

.

Exp. Sta. Res. Bull. 42. 23 pp.

107

Southwood, T. R. E. 1978. Ecological methods. HalstedPress, New York. 524 pp.

Stinncr, R. E., J. R. Bradley, Jr., S. II. Roach, A. W.

Ilartstack, and C. G. Lincoln. 1979. Sampling Ileliothisspecies on native hosts and field crops other thancotton. Pages 146-151. ]m Economic thresholds andsampling of Hel iothis species on cotton, corn, andother host plants. Southern Coop. Series Bull.No. 231. 159 pp.

Strayer, J. R. 1973. Economic threshold studies and sequen-tial sampling for management of the velvetbean cater-pillar. Ant icarsia gemmatalis Ilubner, on soybean.Ph.D. dissertation. Clemson Univ. 87 pp.

Thomas, G. D., D. B. Smith, and C. M. Ignoffo. 1979.Economic thresholds . Iri Introduction to crop protec-tion. Holt, Rinehart and Winston, Inc., New York.

Tietz, H. G. 1972. An index to the described life histories,early stages and hosts of the macrolepidoptera of thecontinental United States and Canada. Allyn Mus . Ent.,Sarasota. 2 Vol.

Trachtenberg, C. H., and D. E. McCloud. 1976. Net photo-synthesis of peanut leaves at varying light intensitiesand leaf ages. Proc. Soil Crop Sci . Soc. Fla. 35:54-5.

Travis, P. A. 1977. Population dynamics of Labidura riparia(Pallas) (Dermaptera: Labiduridae ) , M. S. thesis,Univ. Fla. 86 pp.

USDA. 1977. Field crop summary 1976. Field crop and live-stock reporting service. Florida Agr. Statistics. 9 pp.

van den Bosch, R. , and K. S. Hagen. 1966. Predaceous andparasitic arthropods in California cotton fields.Calif. Agric. Exp. Stn. Bull. 830. 31 pp.

Wall, R. and R. C. Berberet. 1975. Parasitoids associatedwith lepidopterous pests on peanuts; Oklahoma fauna.Env. Entomol. 4:877-82.

Wall, R. G. , and R. C. Berberet. 1979. Reduction in leafarea of Spanish peanuts by the rednecked peanutworm.J. Econ. Entomol. (in review).

Walton, R. R. , and R. S. Matlock. 1959. A progress reportof studies of the red-necked peanutworm in Oklahoma1957 and 1958. Okla. State Univ. Exp. Sta. Proc. Series.P-320. 7 pp.

1U8

Waters, W. E. 1955. Sequential sampling in forest insect

surveys. For. Sci. 1:68-79.

Waters, W. E. and W. R. Henson. 1959. Some samplingattributes of the negative binomial distribution withspecial reference to forest insects. Forest Sci.

5:397-412.

Watt, K. E. F. 1968. Important ecological processes.In Ecology and resource management, McGraw-Hill,N7 Y. 450 pp.

Whitcomb, W. H. 1974. Natural populations of entomophagousarthropods and their effect on the agroecosystem . Pages150-69. In Proceedings of the summer institute on

biologicaT~control of plant insects and diseases. Univ.

Press of Miss. 647 pp.

Whitcomb, W. H., and K. Bell. 1964. Predaceous insects,spiders, and mites of Arkansas cotton fields. Ark.

Agric. Exp. Sta. Bull. 690. 84 pp.

Whitcomb, W. H. , H. A. Denmark, A. P. Bhatkar, and G. L.

Greene. 1972. Preliminary studies on the ants of

Florida soybean fields. Fla. Entomol. 55:129-42.

Williams, J. II., J. H. H. Wilson, and G. C. Bate. 1976.

The influence of defoliation and pod removal on growthand dry matter distribution in groundnuts ( Arachishypogaea L. cv . Makula Red). Rhod. J. Agric. Res.

14: 111-17.

Wolf, D. D. , and R. E. Blaser. 1972. Growth rate andphysiology of alfalfa as influenced by canopy andlight. Crop Sci. 12:23-6.

Young, J. H. , F. R. Cox, and C. K. Martin. 1979. A peanutgrowth and development model. Peanut Sci. 6:27-36.

BIOGRAPHICAL SKETCH

The author was born on October 23, 1951, in Seminole,

Florida. Upon graduation from Seminole High School in 1969,

he entered the University of Florida. In June 1974 he

received the degree of Bachelor of Science with Honors in

Zoology. In the fall of 1974 he enrolled as a graduate

student in the Department of Entomology and Nematology,

College of Agriculture, at the University of Florida, re-

ceiving the Master of Science degree in June, 1976. He

enrolled in the Department of Entomology and Nematology

at the University of Florida during the summer 1976, and

has pursued work toward the degree of Doctor of Philosophy.

He is currently a member of the Entomological Society

of America and the Florida Entomological Society.

109

I certify that I have read this study and that in myopinion it conforms to acceptable standards of scholarlypresentation and is fully adequate, in scope and quality,as a dissertation for the degree of Doctor of Philosophy.'

S. L. Poe, ChairmanProfessor of Entomology

I certify that I have read this study and that in myopinion it conforms to acceptable standards of scholarlypresentation and is fully adequate, in scope and quality,as a dissertation for the degree of Doctor of Philosophy.

W.'^Jonesssociate Professor ofAgricultural Engineering


D. H. HabeckProfessor of Entomology


C. A. Musgrave'Assistant Professor of Entomology

This dissertation was submitted to the Graduate Facultyof the College of Agriculture and to the Graduate Council,and was accepted as partial fulfillment of the requirementsfor the degree of Doctor of Philosophy.

December 1979

Dean, Graduate School

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