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7
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a en ns a

see sc An Informal Conference
er On Liriomyza Leafminers

United States
Department of
PXe la Celli pati get

<<
National Agricultural Library

A aH tO

oe ene

FOREWORD

Liriomyza leafminers (Diptera: Agromyzidae) are economically
important pests on ornamental and vegetable crops in many regions of
the world. Because of the importance of current research views on
Liriomyza leafminers, this conference was organized to help
disseminate information and ideas. These reports describe some of
the current leafminer research being conducted on plant
physiological responses to leafminer damage, biological control
tactics, chemical control tactics, interspecific competition and
visual responses to sticky cards.

Dr. Sidney L. Poe (Department of Entomology, Virginia
Polytechnic Institute and State University, Blacksburg, VA 24061)
and I moderated the conference. This informal conference on
Liriomyza leafminers was part of the National Entomological Society
of America meeting held in San Antonio, Texas, December 1984. We
gratefully appreciate the help and ideas of Drs. Hiram G. Larew and
Ralph E. Webb of the Florist and Nursery Crops Laboratory, USDA.

Trade names are used in this publication solely for the purpose
of providing specific information. Mention of a trade name or
product does not constitute a recommendation, guarantee, or warranty
of the product by the U.S. Department of Agriculture or an
endorsement by the Department over other products not mentioned.

The opinions expressed by the participants at this conference are
their own and do not necessarily represent the views of the U.S.
Department of Agriculture. Mention of a pesticide or a proprietary
product does not constitute endorsement by the USDA.

The papers and illustrations in this publication are reproduced
essentially as they were supplied by the authors. Any questions
concerning them should be addressed to the individual authors.

Janet J. Knodel-Montz

Conference Organizer and Editor
Florist and Nursery Crops Laboratory
USDA, ARS

Beltsville, MD 20705

me a ee we

Copies of this publication may be purchased from the National
Technical Information Service, 5285 Port Royal Road, Springfield, VA
22161. ARS has no additional copies for free distribution...

Issued June 1985

CONTENTS

Plant Physiological Responses to Damage:
Physiological response of vegetables to damage by Liriomyza
trifoliic (Diptera :sAcromyzidae). Jen | el climple ce. ce eee et

Biological Control Tactics:
Parasitization of Liriomyza trifolii by Diglyphus
intermedius. Ke Joa Patel@and D...J. Schiictersa: ene ae

The interaction of parasites and leafminers on commercially
grown chrysanthemum. M. P. Parrella, V. P. Jones, and
G. D. GHLLSELOS for Sie oh ee eee se ee See eee nate e@eee0ee0ee @eeeeed 13

Seasonal abundance of Liriomyza leafminers and their
parasitoids in fresh market tomatoes grown on the west
coastvot Florida. sD...) ochuster... AA Oar =

Impact of currently registered insecticides on the
Liriomyza/parasite complex in celery, 1984. G. W. Zehnder
and Ae Te ET UMD Leo ctatate ocala e eccheveleneseterert okie ec oon etches 21

Progress toward development of an IPM program for Liriomyza
trifolii on greenhouse tomatoes in Ohio. R. K. Lindquist
and M. dling; CASA s.ins.s.6.0 016 eiipeie s/eceie eterera ocetiberececetetatataierciets cia clereaeis ia 28

Chemical Control Tactics:
Neem seed extract products control a serpentine leafminer in
a commercial greenhouse. H. G. Larew, J. J. Knodel-Montz,
ANIC OR go bee We Dbioesse cole cise ie ec erste eter en ee eee

Efficacy of Margosan-0, a formulation of neem, against
Liriomyza trifolii (Burgess) on floral crops.
J. J. Knodel-Montz, H. G. Larew, and R. E. Webb.esercceceee 29

Effects of cryamazine (Trigard!™) on Liriomyza
trifolii (Burgess). G. Lei DEG evo oo anise dicine ee oan ee 45

Interspecific Competition:
Response of Liriomyza trifolii to two-spotted spider mites
and their damage on chrysanthemums. J. F. Price and
GAUROGSE] 5 > ace poe cleo cies a aleiceiata tie ticle cies re en ore
Visual Stimuli:
Responses to visual stimuli: vegetable leafminer compared
with greenhouse whitefly. R. E. Webb, F. F. Smith,
A. M. Wieber, H. G. Larew, and J. J. Knodel-Montz......... 2+

Liriomyza leafminers: potential for management - a summary. 43
S. ile POG reheher so eleresiotereterece ls

Physiological Responses of Vegetables to Damage by
Liriomyza trifolii (Diptera: Agromyzidae)

John T. Trumblel
Introduction

The damage potential of the polyphagous agromyzid,
Liriomyza trifolii (Burgess), has been exhaustively docu-
mented by many researchers (Poe 1982, Spencer 1973). Even
though the economic losses attributed to this leafminer have
recently stimulated considerable research designed to pro-
vide information on 1) leafminer biology (Leibee 1981,
Parrella 1984), 2) chemical control strategies (Schuster and
Everett 1983, Webb et al. 1983), 3) resistance management
(Keil and Parrella 1982), 4) ecology (Zehnder and Trumble
1984, 1984b) and 5) integrated control programs (Trumble and
Toscano 1983), little effort has been made to determine the
physiological responses of the host plant to leafminer
infestations. A notable exception is the study by Johnson
et al. (1983) on the effects of feeding by L. sativae
Blanchard on a commercial variety of tomatoes, Lycopersicon
esculentum (Mill.).

Until the invention of the dual isotope porometer,
statistical analysis of factors influencing photosynthesis
and related processes was extremely difficult and tedious.
The problem was primarily due to the variability in location
and photosynthetic activity of chlorophyll in plants
(Boulanger 1958, Bruinsma 1963). Therefore, predicated on
the availability of the porometer, the research reported
here was conducted to determine the impact of adult feeding
and larval mining on such basic physiological processes as
photosynthesis, transpiration, stomatal conductance and
mesophyll conductance. Related investigations in experimen-
tal plantings in Orange County, California, were designed to
document the effects of various levels of leafminer damage
on plant growth patterns and, ultimately, yield. Much of
the research presented here is the result of a cooperative
study with Dr. Irwin Ting and Loretta Bates of the Botany
and Plant Sciences Department of UCR, and will appear in
1985 in Entomologica Experimentalis et Applicata.

Methods

The dual isotope porometer was used to measure rates of
photosynthesis, transpiration, mesophyll conductance, and
stomatal conductance for celery (Apium graveolens L.) plants
subjected to preselected densities of leafminer damage. The
specific design and operation of the porometer is available
(Johnson et al. 1979) and will not be duplicated here. The

1 yepartment of Entomology, University of California,

Riverside, Calif.

gas exchange equations used to calculate the physiological
parameters are as follows:

CO 2
Photosynthesis in mg CO9/area/time = Reasons and

H20
Transpiration in g H)0/area/time = ia ner sai

where C09 = the difference in concentration of carbon

dioxide between the atmosphere and the
leaf surface,

H90 = the difference in water concentration between
the leaf and the atmosphere,

Rg = the stomatal resistance to H90 or C09 exchange
in cm/sec,

Rm = the resistance of the mesophyll to assimila-
tion of COs in cm/sec.

Initially, a series of twenty undamaged celery plants
were evaluated with the porometer to determine how com-
parable photosynthesis and related parameters were between
specific leaves, petioles, and plants. All celery plants
were of the same variety (5270-R) and seedlot, and grown
under identical conditions in the greenhouse (i.e. soil
type, moisture, light, etc.). Thus, the plants were as uni-~
form as possible. Concurrent with measurements taken with
the porometer, a variety of environmental variables were
monitored, including a) ambient temperature, b) leaf surface
temperature, c) relative humidity, and d) incident
radiation.

All comparisons of leafminer damaged and undamaged
leaves were conducted on the first and second pairs of oppo-
site leaves adjacent to the distal leaf on upright celery
petioles. Since such opposite leaves were determined to be
equivalent in terms of photosynthesis rates, leafminers were
confined to the upper surface on one leaf of each pair of
leaves using small styrofoam cages. To assess the impact of
leafmining, one female and two males were confined per cage
for approximately 1-4 hours, allowing oviposition to occur
at a relatively low rate. Cages were then removed, and
plants were returned to the greenhouse where larvae
completed development and exited the leaves. Only leaves
upon which a single leafminer developed were tested.
Porometer samples were taken distally on the leaf, with the
mined area between the petiole and the sample area. The
same location was then sampled from the opposite, undamaged
leaf. Porometer samples were collected from 120 leaves,
providing 60 comparisons of damaged versus undamaged leaves.

In a second experiment, the physiological impact of
adult feeding was evaluated by confining newly emerged, non-
ovipositing females to the upper surface of one of each pair

of opposite leaves. Following approximately 12 hours of
exposure, cages were removed and plants were transferred to
the greenhouse. The number of feeding punctures on each
leaf disk was counted after sampling with the porometer,
allowing values to be readily converted to feeding punctures
per cm*.

As discussed in the results section, not all leaves,
petioles and plants were comparable in terms of photosynthe-
sis rates and related processes. Therefore, direct, quan-
titative comparisons of rates of each physiological variable
between separate plants, or even petioles within the same
plant, would not be statistically valid. However, opposite
leaves in selected locations were equivalent, and proved
suitable as a substrate for assessing the effects of leaf
miner damage. The analyses presented in Tables 1 and 2 were
therefore generated using a paired t-test which evaluated
whether differences between opposite damaged/undamaged
leaves were significant. Thus, the results shown in these
tables are given as levels of significance at which the null
hypotheses (physiology of damaged leaves = physiology of
undamaged leaves) can be rejected.

A variety of plant growth parameters was monitored
weekly for celery plugs and transplants which were exposed
to high and low levels of leafminer infestations in an
experimental planting of 5270-HK celery in Orange County,
California. All plants were germinated from the same
seedlot and grown to transplant size with the same
greenhouse operation. Populations of L. trifolii were man-
ipulated in the field with weekly pesticide applications:
methamidophos at 1.0 lg ai/acre minimized leafminer density
and methomyl at 0.9 1b ai/acre maximized populations.
Treatments of plugs and transplants were randomized in a
complete block design with each treatment replicated 4
times. Each replicate consisted of 4 beds (2 rows/bed) X 65
ft. Data on mean numbers of mined leaves/plant, plant
height, number of total leaves/plant and numbers of
petioles/plant were collected for 8 weeks following the
first pesticide application. Plant growth was also evalu-
ated at harvest. All statistical analyses were generated
with the Duncan's new multiple range test (DMRT).

Results and Discussion

Comparisons of rates of photosynthesis and related phy-
siological processes between plants, petioles and leaf loca-
tion determined that not all plants, petioles within plants,
or leaves upon petioles are equivalent. In spite of the
uniform growing conditions and appearance of the celery ex-
amined, at least three statistically separate groups of
plants were identified out of the 20 tested. Upright
petioles proved to be more uniform in most physiological
parameters than those petioles deviating from vertical.

This effect is not surprising as petioles with an increasing
horizontal aspect frequently had begun to senesce, exacer=
bating the variability in chlorophyll activity.

Fortunately, some opposite leaves were comparable. The
first and second pairs of opposite leaves adjacent to the
distal leaf on vertical petioles were not significantly dif-
ferent in any of the physiological parameters tested for any
of the 20 plants. Leaves at other locations on the petiole
had either much higher or much lower levels of activity.
Therefore, the first and second pairs of opposite leaves
were utilized as sample substrates throughout this study.

The impact of leafmining on celery physiology is pre-
sented in Table 1. A single leafmine significantly reduced
stomatal conductance, mesophyll conductance, transpiration
and photosynthesis. These results are generally in
agreement with those of Johnson et al. (1983), where L.
sativae was shown to cause similar reductions in photo-
synthesis and transpiration. Clearly, a disruption of the
vascular system in celery affects the movement of water
which, in turn, causes changes in turgor pressure. This
results in a reduction in stomatal conductance, which inhi-
bits transpiration and, ultimately, photosynthesis.

The effects of feeding damage by adult L. trifolii on
celery physiology is presented in Table 2. Feeding punc-
tures occurring at a density of less than ca. 13/cm2 did not
affect any of the physiological parameters evaluated.
However, between 13-19 punctures/cm2, a low level, all pro-
cesses were significantly reduced. Since the density of
feeding/oviposition punctures frequently exceeds this level
in the field, the previous view that such damage was negli-
gible may not be valid.

Relative leafminer damage was compared between cultural
and chemical treatments using the data on percentages of
mined leaves per plant (Table 3). No significant differen-
ces in percent of mined leaves per plant were found for
eight week averages. Unfortunately, information on percent
mined leaves per plant does not provide accurate comparisons
between treatments unless several other factors are con-
sidered, including leafminer larval survival and rates of
parasitism. In addition, plant height, number of petioles,
and number of leaves per plant should be taken into account
or data on the percent of mined leaves per plant will not be
biologically significant.

Leafminer larval survival was significantly reduced in
methamidophos treated celery, but survival increased in
plots sprayed with methomyl. Also, percent parasitism
(based on leafminer and parasite emergence) was signifi-
cantly greater in control and methamidophos treatments (ca.
50%) than in celery sprayed with methomyl (ca. 25%). Thus,
even when the percentages of mined leaves were not different

between treatments, more mines contained dead or parasitized
larvae in the methamidophos treatments than celery where
methomyl was applied. A general decrease in the size of
mines and a corresponding reduction in physiological damage
to the test plants resulted.

The effect of leafminer feeding on plant height has
been shown in Table 4. On each sampling date, plants
treated with methomyl were smaller than those treated with
methamidophos. Differences in height were significant
(P=0.05 level, DMRT) between chemical treatments on five of
the eight sampling dates. Since smaller plants have fewer
leaves and less leaf area per leaf, small plants would be
more seriously affected by leafminer damage at a given per-
cent infestation than plants with greater size. A com-
parison of chemically treated plants with control plants
(untreated) found that both damage and plant height param=-
eters were intermediate for control plants, indicating that
leafminer damage and not chemical phytotoxicity was the pri-
Mary cause of variation in plant growth.

The mean numbers of leaves per plant were also signifi-
cantly different (P=0.95, DMRT) between treatments (Table
5). Transplants had more leaves than plugs on every
sampling date, and transplants sprayed with methamidophos
had significantly more leaves than those treated with metho-
myl on six of the eight sampling dates. In four of the last
six samples, plugs treated with methomyl had significantly
fewer leaves than plugs exposed to methamidophos.

As a result of slower growth due to leafminer damage,
plugs sprayed with methomyl developed significantly fewer
petioles than all other treatments (Table 6). By the
seventh week of sampling, plugs treated with methamidophos
had as many petioles as transplants in the methomyl treat-
ment. Only those transplants where leafminer damage was
suppressed with methamidophos produced more petioles.

Acknowledgements

The assistance of H. Nakakihara, W. Carson and J.
Feaster in the field is appreciated. Bud of California pro-
vided the plugs, and Mr. J. Fuji provided seeds and
transplants. This research was supported in part by grants
from the California Celery Research Advisory Board and the
Academic Senate of the University of California, Riverside.

Table 1. Impact of leafmining by L. trifolii on selected physiological
parameters of celery.

Paired

Physiological process Units comparison analysis*
Stomatal conductance cm/sec >0.001
Mesophyll conductance em/sec >0.001
Transpiration g H90/area/time >0.002
Photosynthesis mg CO9/area/time >0.001

ree

=n = 60 comparisons, values indicate level at which the hypothesis

"physiology of damaged leaves = phystology of undamaged leaves"
can be rejected.

Table 2. Relationship between density of feeding punctures of L.
trifolii and celery physiological processes.

re ee a
Feeding Paired comparison analysis®*

punctures Stomatal Mesophyll
per sq- cm conductance conductance Transpiration Photosynthesis
0 - 6.3 NS NS NS NS
6 .4-12.7 NS NS NS NS
1248-1931 NS NS NS 0.1
eS ales 0.01 0.001 0.02 0.001

ee eee eee ee

@NS = not significant at P<0.05; values indicate level at which the
hypothesis “physiology of damaged leaves = physiology of un-
damaged leaves" can be rejected.

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References Cited

Boulanger, L. W. 1958. The effect of european red mite
feeding injury on certain metabolic activities on red
delicious apple leaves. Maine Agric. Expt. Sta. Bull.
570. 34 pp.

Bruinsma, J. 1963. The quantitative analysis of

chlorophylls a and b in plant extracts. Photochem.
Photobiol. 2: 241-249.

Johnson, H. B., P. G. Rowlands, and I. P. Ting. 1979.
Tritium and carbon-14 double isotope porometer for
simultaneous measurements of transpiration and photo-
synthesis. Photosynthetica 13: 409-418.

Johnson, M. W., S. C. Welter, N. C. Toscano, I. P. Ting, and
J. T. Trumble. 1983. Reduction of tomato leaflet pho-
tosynthesis rates by mining activity of Liriomyza
sativae (Diptera: Agromyzidae). J. Econ. Entomol.

76: 1061-1063.

Keil) C.B. J and M. P.)Parrella.” 1982. Lirtomyza trifolii
on chrysanthemums and celery: managing an insecticide
resistant population. pp. 162-167 In: S. L. Poe (ed.),
Proc. Third Annual Ind. Conf. on the Leafminer. Nov.
8-10, San Diego, CA. 116 pp.

Leibee, G. L. 1981. Development of Liriomyza trifolii on
celery. pp. 35-41 In: D. J. Schuster (ed.), Proc.
Second Annual Ind. Conf. on the Leafminer. Nov. 3-4,

Lake Buena Vista, FL. 235 pp.

Parrella, M. P. 1984. Effect of temperature on oviposi-
tion, feeding and longevity of Liriomyza trifolii
(Diptera: Agromyzidae). Can. Entomol. 116: 85-92.

Poe, S. L. (editor). 1982. Proc. Third Annual Industry on
the leafminer. Nov. 8-10, San Diego, CA. 216 pp.

Schuster, D. J., and P. H. Everett. 1983. Response of

Liriomyza trifolii (Diptera: Agromyzidae) to insec-
ticides on tomato. J. Econ. Entomol. 76: 1170-1174.

Spencer, K. A. 1973. Agromyzidae (Diptera) of economic
importance. Ser. Entomologica 9. Dr. W. Junk, The
Hague. 418 pp.

Trumble, J. T., and N. C. Toscano. 1983. Impact of metha-
midophos and methomyl formulations of Lirtomyza species
(Diptera: Agromyzidae) and associated parasites in
celery. Can. Entomol. 1415-1420.

Webb, R. E., M. A. Heinbaugh, R. K. Lindquist, and M.
Jacobson. 1983. Evaluation of aqueous solution of
neem seed extract against Liriomyza sativae and L. tri-~

folii (Diptera: Agromyzidae). J. Econ. Entomol. 76:

Zehnder, G. W. and J. T. Trumble. 1984a. Host selection of
Liriomyza spp. (Diptera: Agromyzidae) and associated
parasites in adjacent plantings of tomatoes and celery.
Environ. Entomol. 13: 492-496.

Zehnder, G. W. and J. T. Trumble. 1984b. Spatial and diel
activity of Liriomyza species (Diptera: Agromyzidae)
in fresh market tomatoes. Environ. Entomol. 13:
1411-1416.

Parasitization of Liriomyza trifolii
by Diglyphus intermedius

K. J. Patell and D. J. Schuster2

Summary

Diglyphus intermedius (Girault) is one of 4 major
parasitoids attacking Liriomyza spp. leafminers which infest
fresh market tomatoes on the west coast of Florida. Despite
the abundance of this parasitoid, relatively little is known
regarding its basic biology. In previous studies, we found
that developmental rates of D. intermedius eggs, larvae and
pupae were quadratically related to temperature with highest
developmental rates occurring at about 27° C. The purpose
of the present investigation was to evaluate the selected
factors affecting oviposition.

Fecundity, longevity and host mortality of D.
intermedius were studied at 5 constant temperatures ranging
from 15.6 to 31.1° C. One-day-old parasitoids were provided
20, 3rd instar L. trifolii (Burgess) larvae in excised tomato
leaflets every 24 hrs. The circadian pattern of oviposition
was studied by providing 5-day-old parasitoid females with 15
3rd instar L. trifolii larvae in excised tomato leaflets
every 4s tow? \hourssotmanl2u:12)) day... To. study host. size
preference, 5-day-old parasitoid females were simultaneously
plovided. 20.4 °2nd yinstanwands 20, 3rdisinstar jbeetrifolid) in
excised tomato leaflets for a 4 hr _ period. kngica 4.
experiments, dead leafminer larvae were dissected from the

foliage and the presence of parasitoid eggs determined.

The fecundity of D. intermedius was related
quadratically to temperature. Oviposition increased slightly
as temperature increased from 15.6 to 19.4° C, but decreased
sharply above 23.3° C. Large numbers of L. trifolii larvae
were killed in the absence of oviposition (host feeding).
The relationship of temperature to host feeding was inversely
linear. This effect was apparently due to the effect of
temperature on longevity which also declined linearly as
temperature increased. D. intermedius oviposition and host
feeding was greatest during the first 4 hours after lights
were turned on. Activity was much less during the next 8 hr
period, and practically ceased after lights were turned
Oli wel. intermedius preferred) Snd\anstaral. ;trifolis wlarvae
for oviposition and host feeding; however, 2nd instar larvae
were also utilized.

IDepartment of Entomology & Nematology, University of Florida,
Gainesville, Fi 32611,

University of Florida, Gulf Coast Research and Education,
5007 60th St. E., Bradenton, FL 34203.

D. intermedius appears to be a very good parasitoid of
L. trifolii when considering the combined mortality inflicted
by oviposition and host feeding. However, these studies
were conducted under conditions of high host abundance.
Searching capacity and efficiency must be further evaluated.
Under high temperature conditions, D. intermedius appears to
be much less suitable since developmental rates, oviposition,
host feeding and longevity are less at high temperatures.
This may at least partially explain why L. trifolii
populations increase dramatically in the spring an Florida.

The Interaction of Parasites and Leafminers
on Commercially Grown Chrysanthemum

M. P. Parrellal, Ver. Jones!, and G. D. Christie!

Biological control of arthropods on an ornamental crop
such as chrysanthemum is generally considered unfeasible due
to the high aesthetic value of the crop. For this reason,
the application of biological control on most ornamentals is
thought to be impossible throughout much of the world
(Lenteren et al. 1980). However, this is not true with
chrysanthemums grown for cut flowers for several reasons.
First, only the upper two-thirds of the plant is harvested
with the remainder left in the bed to be tilled under.

Thus, the lower plant foliage (the first 4-6 weeks of crop
growth) can be damaged without affecting the marketed com-
modity. Second, the leafminer, Liriomyza trifolii
(Burgess), has developed resistance to numerous insecticides
and is very difficult to control even with repeated applica-
tions of highly toxic materials (Keil et al. 1985). There-
fore, growers may be able to obtain a crop of good quality
using biological control of leafminers which would be equal
to that provided by the use of insecticides. This may stim-
late the adaption of biological control on chrysanthemum in
much the same way as the development of pesticide resistance
in Tetranychus urticae Koch (Acari: Tetranychidae) in
Europe after World War II revived the application of biolo-
gical control on vegetables (Lenteren et al. 1980). Third,
effective leafminer insecticides are available which are
compatible with natural enemies (Parrella et al. 1983a,
Pettit et al. 1984). Control exerted by natural enemies and
the pesticide may lessen selective presssure on L. trifolii
to develop resistance to the chemical, therefore, effec-
tively increasing its useful field life. In addition,
growers may be willing to adopt biological control if they
recognize that any new chemical is but a temporary solution
to the problem.

Biological control of the leafminer, Chromatomyia
syngenesiae Hardy, on chrysanthemum has been successfully
achieved in England with several species of parasites (Cross
et al. 1983). This leafminer species has a much lower
reproductive potential than L. trifolii (Parrella et al.
1983b, Cohen 1936), and pupates within the leaf. Conse-
quently, the tactics employed in England may not be applica-

luniversity of California, Riverside, CA 92521.

ble to biological control of L. trifolii on chrysanthemum.
Also, while insecticide resistance has been demonstrated for
C. syngenesiae (Hussey 1969), this species is considered to
be far more susceptible to pesticicides than Geter ifoliys
(Lindquist et al. 1984).

Research on biological control of L. trifolii on chry-
Santhemum has been limited (Prieto and Chacon 1980, Price
et al. 1981). Price et al. (1980) indicated that improved
management techniques for L. trifolii on chrysanthemum are
needed before the full potential of integrated pest manage-
ment on this crop can be realized. Here, we report a brief
summary of a study where parasites alone and parasites plus
an insect growth regulator (IGR) were used in feasibility
Studies to evaluate control of L. trifolii on commercially
grown chrysanthemum. Control obtained through inoculative
releases of parasites and immigration by natural parasite
fauna was compared to normal grower practices. A second
objective was to evaluate the response of the parasites to
an increasing L. trifolii population on chrysanthemum,

Materials and Methods

A greenhouse was chosen in Carpinteria (Santa Barbara
Co.) that encompassed ca. 2.5 ha. Three greenhouse rooms (6
m wide X 30 m long), each with 3000 "Manatee Iceberg' chry-
Santhemum plants, were isolated from One another with fine
mesh screening (40 holes/2.5 cm2). While this did not
completely exclude parasites or flies from moving between
adjacent greenhouses, it did Significantly curtail their
movement. Each greenhouse was a Separate treatment:

Greenhouse #1 - 'Parasite House' with parasite releases
only, no pesticide until late in the crop

Greenhouse #2 - Trigard House with parasite releases plus
Cyromazine 75W at low rates (11.3 g ai/acre)

Greenhouse #3 - 'Grower House' with pesticide applications
of permethrin 3.2 plus microencapsulated methyl
parathion 2E two times per week at recommended rates

The schedule for releases of L. trifolii parasites and
application of cyromazine is provided (Table 1). The para-
site, C. parksi, was selected as the species to release
early in the crop for several reasons: (1) Mass-rearing is
possible, (2) this Species is a larval-pupal parasite and
parasitized pupae can be quickly separated from those
uNparasitized (therefore, pupae can be directly released),

Table l

Schedule for biological control trial, Carpinteria - 1983.

Week Strategy

1/24 Crop planted, 3000 plants/treatment

2/18 600 L. trifolii released (all treatments)?

3/1 700 C. parksi released (parasite and cyromazine
treatment )@

4/8 600 C. parksi released (parasite and cyromazine
treatment )4

5/12 150 C. parksi released (parasite and cyromazine
treatment )?

6/20 cyromazine applied in cyromazine treatment

143 cyromazine applied in cyromazine treatment

8/17 cyromazine applied in cyromazine and parasite
treatment

9/24 cyromazine applied in cyromazine treatment

10/31 cyromazine applied in cyromazine and parasite
treatment

4 50:50 female: male

(3) the fecundity is relatively high and development time
short compared to other genera of leafminer parasites
(Christie 1984), and (4) this species is compatible with low
rates of cyromazine (Parrella et al. 1983a).

Sampling and Analysis.

All plants in each greenhouse were numbered and 16
plants/greenhouse were sampled randomly each week by
removing 3 leaves from the top, middle and bottom strata of
each plant. Leaves were placed in friction sealed petri
dishes and returned to the laboratory where mines with live
larvae were counted with the aid of transmitted light. Dead
mines were also recorded. Leaves were returned to petri
dishes and held for the emergence of pupae and subsequent
emergence of adult flies or parasites.

Eight yellow sticky cards (7.6 cm X 12.4 cm) were
spaced uniformly down the center of each greenhouse. These
were held just above the plant foliage at all times during
the trial. All flies and parasites caught on the traps were
counted weekly and mean numbers of parasites and flies were
calculated per sticky trap/week.

Means were calculated for live mines, dead mines, adult
flies, and adult parasites per leaf/strata/greenhouse.
Percent parasitism (adult parasites/adult flies + adult
parasites) was also determined. ANOVA and Duncan's new
multiple range test were used to Separate means,

Results and Discussion

Throughout most of the season, all three houses had
similar numbers of flies caught on yellow traps. This is a
reflection of the insecticide resistance capability of L.
trifolii at this location. Very few C. parksi were found on
sticky traps or in leaf samples. Preliminary data suggest
that the temperature in these greenhouse (which exceeded
37°C at times) was in excess of what could be tolerated by
C. parksi. A large number of the natural parasite fauna,
which were present around the greenhouse, moved into this
trial in response to the leafminer populations. As
expected, few parasites were trapped in the grower house, a
moderate number in the Trigard house and large numbers in
the parasite house. These consisted mostly of Diglyphus
Spp., and the mention of parasites from now on will refer to
members of this genus. In addition, only data from the
parasite house will be discussed.

Comparing the number of live mines and pupae by strata,
greater numbers were found in the bottom and middle strata
compared to the top. During the middle dates (weeks 6, 7
and 8), more live mines and pupae were found in the middle
strata as compared to the bottom. Dates before this did not
have a middle strata because plants were too short.
Examining Diglyphus spp., the distribution of dead mines and
parasites followed a similar pattern as described above,
although higher numbers were not found in the middle strata
compared to the bottom. This was surprising and suggests
that the parasites are not responding adequately to leaf-
miners in the middle of the chrysanthemum plant. Overall
parasitism throughout the season was low. However, parasi-
tism did reach high levels on specific dates (>85%).

The failure to establish C. parksi was attributed to
excessive greenhouse temperatures but this did point out the
need to augment the natural Parasite fauna. In the parasite
house, the crop produced was not marketable, despite high
numbers of parasites and applications of cyromazine late in
the crop. The need to make parasite releases early when the

infestation of leafminers is low is imperative in order to
insure adequate plant quality. A further complicating fac-
tor was that at planting time, every transplant was infested
with one or more live larvae of L. trifolii. This, together
with releasing L. trifolii in all the treatments, produced a
heavier-than-expected fly population. However, a marketable
crop of chrysanthemums was produced in the parasite plus
Trigard house, which demonstrates the compatibility of these
two methods of control. In addition, the quality of this
crop was as good as that produced in the grower house.

Acknowledgments

We thank Dr. C. B. Keil (Department of Entomology and
Applied Ecology), Mr. J. A. Bethke, A. Urena C. Wait, J.
Virzi and K. L. Robb (Department of Entomology, University
of California, Riverside for technical assistance. This
research was supported by the American Florists Endowment.

Literature Cited

Christie, G. D. 1984. Biological studies on Chrysocharis
parksi (Hymenoptera: Eulophidae), an endoparasite of
Liriomyza trifolii (Diptera: Agromyzidae). Ms. Thesis,
Univ. of Calif., Riverside, 60 pp.

Cohen, M. 1936. The biology of the chrysanthemum leaf-
miner, Phytomyza atricornis Mg. (Diptera: Agromyzidae).
Ann.* Appl] .""BidIh® 23'3 Wh G12-632%

Cross, J. V., L. R. Wardlow, R. Hall, M. Saynor, and P.
Bassett. 1983. Integrated control of chrysanthemum
pests. Proc. Working Group Integ. Control in glass-
houses. Bull. SROP VI/e: 181-185.

Hussey, N. W. 1969. Differences in susceptibility of dif-
ferent strains of chrysanthemum leaf miner (Phytomyza
syngenesiae) to BHC and diazinon. Proc. 5th Br.
Insectic. Fungic. Conf.: 93-97.

Keil, C. B., M. P. Parrella, and J. G. Morse. 1985. Method
for monitoring and establishing baseline data for
resistance to permethrin by Liriomyze trifolii
(Burgess). J. Econ. Entomol. (in press)

Lenteren, J. C., van, P.M.J. Ramakers, and J. Woets. 1980.
Med. Fac. Landbouww. Rijksuniv. Gent. 45/3: 537-544.

Lindquist, R. K., M. L. Casey, N. Helyer, and N.E.A. Scopes.
1984. Chromatomyia syngenesiae and Liriomyza trifolii
control on greenhouse chrysanthemum. J. Agric.
Entomol. (in press)

Parrella, M. P., G. D. Christie, and K. L. Robb. 1983a.
Compatibility of insect growth regulators and
Chrysocharis parksi (Hymenoptera: Eulophidae) for the
control of Liriomyza trifolii (Diptera: Agromyzidae).
J. Econ. Entomol. 76: 949-951.

Parrella, M. P., K. L. Robb, and J. Bethke. 1983b.
Influence of selected host plants on the biology of
Liriomyza trifolii (Diptera: Agromyzidae). Ibid. /76:
112-115.

Pettit, ukteLs. Ct: Se aHalliday.@DogMomocott,sand D. J.
Vondal. 1984. Toxicity of Trigard 75W to Tetranychus
urticae (Acari: Tetranychidae) and the predatory mite
Phytoseiulus persimilis (Acari: Phytoseiidae) and its
effect on egg consumption by the predator. Proc.
Fourth Ann. Indust. Conf. of the Leafminer. Sarasota,
Fla’. taippsg 0-3.

Price, J. F., L. D. Ketzler, and C. D. Stanley. 1981.
Sampling methods of Liriomyza trifolii and its parasi-
toids in chrysanthemums. Proc. IFAS - Ind. Conf. on
the Biol. and Control of Liriomyza Leafminers, Lake
Buena Vista, Fla. pp. 156-157.

Price, J. F., A. J. Overman, A. W. Englehard, M. K. Iverson,
and V. W. Yingst. 1980. Integrated pest management
demonstrations in commercial chrysanthemums. Proc.
Fla. State Hort. Soc. 93: 190-194

Prieto, A. J., and P. Chacon. 1980. Biologia y ecologia de
Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)
minador del crisantemo en el Department del Canca.
Revista Colomb. Entomol. 6: 77-84.

Seasonal Abundance of Liriomyza Leafminers and Their
Parasitoids in Fresh Market Tomatoes Grown
on the West Coast of Florida

D. J. Schuster!
Summary

Hymenopterous parasitoid species are important in the
population dynamics of Liriomyza spp. Many studies have been
conducted to determine the parasitoid species attacking
Liriomyza on tomato. The most abundant parasitoids vary by
location and season. Data from Florida have been collected
from insecticide evaluation plots. The objectives of the
present study were to monitor Liriomyza and parasitoid
species in insecticide sprayed and nonsprayed, fresh market,
Staked tomatoes.

The studies were conducted in the fall production season
of 1980 and the spring production seasons of 1981, 1983 and
1984, In 1980 and 1981 0.4 ha fields of tomatoes were grown
at GCREC Bradenton and were divided into 15 equal sections.
Two to three weeks after planting, one plant was selected
twice weekly from each of at least five sections. At each
sampling, all leaflets containing occupied leafmines were
held” in-*containers’ in’ the) Evaboratory until adults “had
energed> “In 1983, “six commercial fields “were ‘divided
such that there was at least one sampling site per ha. Each
site was sampled twice weekly by examining the terminal three
leaflets of the fourth leaf from the top of six branches.
Leaflets containing occupied leafmines were held in the
laboratory for adult emergence. Two of the six fields were
Similarly sampled in 1984, In 1980 and 1981 the tomatoes
were not sprayed with insecticide. In 1983 and 1984, the
tomatoes were sprayed according to the normal practices of
each grower.

L. sativae Blanchard was the most abundant leafminer in
1980 and 1981, and peaked in the mid to late season. L.
trifolii (Burgess) was more abundant in 1981 and peaked in
the early season. In 1983 and 1984, L. trifolii was the most
abundant leafminer. L. sativae was much less abundant and
peaked in the early season. Over 95% of the hymenopterous
parasitoid yacults* recovered” were of” four “species.” Opius
sp. and Chrysonotomyia formosa (Westwood) were most abundant
in 1980; Diglyphus intermedius (Girault) was most abundant in
1981; and C. formosa was most abundant in 1983 and 1984.
Opius sp. and D. intermedius were of moderate abundance in
1983 and Halticoptera circulus (Walker) was of moderate

abundance in 1984.

lUniversity of Florida, Gulf Coast Research and Education
Center, 5007 60th St. E., Bradenton, FL 34203.

Lhe

During the course of these Studies there was an apparent
shift in predominant leafminer species from L. sativae (most
abundant in 1980) to L. trifolii (most abundant in 1984).
This apparent shift may be due to a displacement of one
Species by another because of competition or, perhaps more
likely,» because’ of themuse of insecticides. Permethrin and
methamidophos were the insecticides used early in 1984 at the
time L. sativae densities decreased. The relative abundance
of parasitoid species varied from one season to another.
Considering Proportions, QOpius sp. and D. intermedius were
more abundant in nonsprayed tomatoes than in sprayed
tomatoes. Conversely, C. formosa was more abundant in
Sprayed tomatoes.

Impact of Currently Registered Insecticides on the Liriomyza/Parasite
Complex in Celery, 1984.

Geoffrey W. Zehnder. and John T. mrumbles

Abstract

Six insecticides (Ambush 25W, Diazinon 50W, Dibrom 8E, Monitor 4E,
Phosdrin 4E, and Thiodan 50W) were evaluated for control of Liriomyza species
leafminers in celery and impact on associated parasite species. Pupal tray
surveys indicated that Ambush treatments resulted in significantly higher leaf-
miner populations and greater parasite mortality than other insecticide treatments
Or the control. Differential parasite survivorship occurred among treatments.
A greater percentage of Chrysonotomyia punctiventris emerged from organophosphate-
treated leaf samples, while Ambush treatments yielded a higher percentage of
Diglyphus species parasites.

Introduction

Liriomyza trifolii (Burgess) has become an increasingly serious pest in
California celery since its introduction from Florida in the late 1970's
(Parrella et al. 1981). Resistance of L. trifolii to most classes of insecti-
cides has been documented in Florida (Leibee 1981), where pesticides have been
widely applied to celery for approximately 30 years. A 20-fold increase in
resistance to permethrin has been reported for DL." tereols1 collected” from’ green-
houses in California (Parrella and Keil 1984). The importation of resistant flies
from Florida is undoubtedly a factor in the failure of most insecticides used for
control of this pest in California.

In recent years, methamidophos Henin 4 has been one of the few insecticides
proven effective in controlling leafminers in celery without suppressing parasite
populations (Trumble and Toscano 1983). Unfortunately, residue levels at harvest
have exceeded legal tolerances and use of methamidophos has been restricted in
California. Other registered compounds have not recently been evaluated for
control of leafminers and concurrent effect on associated parasite species. We,
therefore, conducted field experiments to compare five compounds, currently
registered for leafminer control in celery, with a standard methamidophos treatment.

Materials and Methods

Tall Utah 52-70 HK celery was transplanted August 10, 1984, at the University
of California south Coast Field Station, Santa Ana, California. The crop was
sprinkle-irrigated for three weeks and furrow-irrigated thereafter. Treatments
were applied to single-bed replicates, 30 feet long with 3.5 feet of untreated
row, Or one untreated bed between replicates. Each bed contained two rows of
plants 6 - 8 inches apart. Treatments were replicated four times in a randomized
complete block design. Insecticides were applied weekly with a B&G co. hand

bagel Truck and Ornamentals Research Station, Rte. 1, Box 133, Painter,
Virginia 23420.

enepe: of Entomology, University of California, Riverside, Calatornva 9252 1%

faa

Sprayer from September 14 through October 26. ‘Two drop nozzles were utilized
per bed with D3 orifice discs and #25 cores. The delivery rate was 100 gallons/
acre with a wand pressure of 40 psi. All insecticide treatments included 0.04
percent spreader-sticker (Leaf Act 40).

Four plants per replicate were randomly selected and one mined (active or
inactive) trifoliate from the upper and lower portion of each plant was sampled
(8 trifoliate samples per replicate). Leaf samples were taken every other week
from September 20 through October 18. Parasites emerging from leaves were counted
and identified to species. The numbers of dead leafminer larvae in the leaves
were also recorded.

Four 8 x 4 inch styrofoam pupal trays per replicate were placed between rows
of plants from October 4 through November 1. Numbers of leafminer pupae and dead
leafminer parasites in the trays were recorded weekly.

Results

Liriomyza pupal counts averaged for the entire season were higher in all
of the insecticide plots than in the control, with significantly more pupae in
the Ambush, Dibrom, and Phosdrin plots than in the control (Table 1). Fewer
dead Liriomyza larvae were observed in the Ambush-treated leaves than in the
control (Table 2), also suggesting that Ambush was not effective in controlling
leafminer populations.

A possible factor contributing to the low efficacy of Ambush may be selective
toxicity towards leafminer parasites. Greater numbers of dead leafminer parasites
were observed in pupal trays under Ambush-treated plants than in other treatments
Or the control (Table 3). Analysis of data from leaf samples indicated that
approximately 1.5 parasites per 2 trifoliates emerged from Ambush-treated leaves
On September 20, 6 days after the first spray application. Parasite numbers in
the Ambush plots continued to decrease thereafter, with less than 0.2 parasites
per 2 trifoliates emerging from the October 18 sample.

The three most common parasite species reared from leaf samples were Diglyphus
intermedius (Girault), D. begini (Ashmead), and Chrysonotomyia punctiventris
(Crawford) (Table 4). In the Organophosphate-treated plots (Dibrom, Diazinon,
Monitor, Phosdrin) 51-60 percent of emerged parasites were C. punctiventris.

In contrast, the Ambush plots yielded OnlYpoz percent C. punctiventris and 68 per-
cent Diglyphus species. This data suggests that C. punctiventris may have some
level of tolerance to the organophosphates while Diglyphus species are susceptible
to organophosphates and not affected by Ambush, a synthetic pyrethroid. In another
Study utilizing larger plot size, Diglyphus species proved to be tolerant and

C. punctiventris was more susceptible to the Organophosphate, methamidophos
(Trumble and Toscano 1983). These contrary results suggest that other factors

may be involved in apparent differential susceptibility between parasite species.

Additional work needs to be done to determine relative toxicity of the more
frequently used insecticides towards leafminer parasites. Recent field studies
have demonstrated that leafminer Parasites are able to discriminate between
potential habitats or leafminer host species (Zehnder and Trumble 1984). Know-
ledge of parasite host or habitat preference, along with information on relative
toxicity of various insecticides to endemic parasites, would be useful in
managing leafminer pesticide Programs to conserve natural enemies.

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References Cited

Leibee, G. I. 1981. Development of Liriomyza trifolii (Burgess) on celery.
pp. 35-41. In D. J. Schuster (ed.), Proc. IFAS-Ind. Conf. Biol. Control
Liriomyza Leafminers. II. Lake Buena Vista, Fla.

Parrella, M. P., W. W. Allen, and P. Morishita. 1981. Leafminer species causes
California mum growers new problems. Calif. Agric. 35:28-30.

Parrella, M. P., and C. B. Keil. 1984. Insect pest management: the lesson of
Liriomyza. Bull. Ent. Soc. Am. 302) 222-25.

Trumble, J. T. and N. C. Toscano. 1983. Impact of methamidophos and methomyl
on populations of Liriomyza species (Diptera: Agromyzidae) and associated
parasites in celery. Can. Ent. 115:1415-1420.

Zehnder, G. W. and J. T. Trumble. 1984. Host selection of Liriomyza species
(Diptera: Agromyzidae) and associated parasites in adjacent plantings of
tomato and celery. Environ. Entomol. 13:492-496.

PROGRESS TOWARD DEVELOPMENT OF AN IPM PROGRAM
FOR Liriomyza trifolii ON GREENHOUSE TOMATOES IN OHIO

R. K. Lindquist and M. L. Casey
Department of Entomology
OARDC/OSU
Wooster, OH 44691

The goal of this project is to develop a practical IPM program for
greenhouse tomatoes. Leafminers are major components of a pest complex
that also includes whiteflies, spidermites, thrips, aphids and caterpillars.
Our work with leafminers includes insecticide evaluation, selecting
leafminer-resistant plants, leafminer parasite biological studies, and
economic injury level evaluations. As a part of these studies, an experiment
was conducted on greenhouse tomatoes during 1984. After a L. trifolii
infestation was established on transplanted tomatoes, Diglyphus parasites
were released. Following this, treatments consisting of parasites only,
methomyl sprays every 14 days, and cryomazine sprays every 14 days were
established in the greenhouses. Four plants were treated with each pesticide.
We recorded leafminer and parasite adult activity during the cropping season
using yellow sticky traps. Also, the number of completed, active and
parasitized/dead leafmines on entire plants was recorded on several
occasions. Pupae were collected in trays below plants and counted. Finally,
fruit yields were recorded.

Results from yellow sticky traps indicated that adult leafminer activity
peaked in week 3 (after transplanting) and week 10. Diglyphus adult
activity peaked on weeks 12 and 18, with few or no adults trapped prior to
week 10.

Significantly more pupae were collected from methomyl-treated plants
than on untreated (parasites only) or cryomazine-treated plants, indicating
an adverse effect of methomyl on parasites. By the end of the experiment,
however, parasites had become well established on methomyl-treated plants,
so this effect was temporary. Similarly, higher numbers of dead/parasitized
larvae were recorded initially from cyromazine-treated plants than on
methomyl-treated plants. Untreated plants (parasites only) had intermediate
numbers of dead/parasitized larvae.

Fruit yields (weight only) were not Significantly different among any
of the treatments. We are presently evaluating the number of leafmines
per leaf to determine the actual leafminer population on individual plants
at various times during the crop.

Neem Seed Extract Products Control
a Serpentine Leafminer in a Commercial Greenhouse!

Hiram G. Larew, 2 leis Knodel-Montz, 2
and Ralph E. Webb2

Abstract

Applied as a soil drench to bed grown chrysanthemums, 0.4% crude
neem seed extract and 0.33% Margosan-O” (an experimental
formulation of neem seed extract) caused significant pupal mortality
of Liriomyza trifolii (Burgess) in an infested commercial
greenhouse. Both crude neem seed extract and Margosan-O were as
effective as Trigard! in disrupting the insect's life cycle.

Summary of Experimental Design and Results

Seeds of the neem tree (Azadirachta indica A. Juss) have long
been used as a source of insect repellents and insecticides
(Jacobson 1981). The systemic activity of neem seed extract has
been reported (Gill and Lewis 1971; Larew et al. in press). We
conducted our experiment in a commercial greenhouse (Perry Hall, MD)
infested with L. trifolii. We compared efficacies of crude neem
seed extract and Margosan-O to that of Trigard!M (Ciba-Geigy), an
insecticide known to be effective against leafminers (Price, 1984).

Lh Mention of a product does not constitute an endorsement by
the USDA.
Florist and Nursery Crops Laboratory, Building 470, Beltsville
Agricultural Research Center, USDA/ARS, Beltsville, MD 20705
3/ Submitted for EPA registration and for patent by Vikwood, Ltd.,
Sheboygan, WI.

Daytime temperatures in the greenhouse ranged from 25-359,
Weekly monitoring with 29.5 cm x 15.0 cm Sticky Strips!M (0lson
Products) indicated a constant and heavy infestation of Mic gmesni ow tal
throughout the experiment (mean = 1805 adults/strip/wk). The
greenhouse was continuously planted with chrysanthemums (i.e. there
were plants of various ages in the greenhouse while we conducted the
experiment). For our experiment, rooted cuttings of cv. Hartmann's
Dignity were planted 10 per row in a 23 m by 1.5 m section of ground
bed on March 19, 1984. The crop was grown in topsoil to which 1
bale of peat moss per 23 m2 of bed space had been added. Plants
were grown as single stem disbuds (LD from planting until April 10;
SD from April 11 until bloom; disbudded May 14; bloomed June 13,
1984).

Treatment plots were 2.3 m long (15 rows/plot; 150
plants/plot) and were marked off next to each other along the bed.
Plots were partitioned with plastic from the soil surface down to 15
cm below ground, and 4 rows of plants between plots were left as
unsampled buffer zones. There was one plot per treatment and
treatments were randomly assigned. Treatments began one week after
planting and continued biweekly until 2 weeks before bloom.

Sampling began two weeks after planting and continued biweekly until
1 week before bloom. Plots were both treated and sampled five times
each. At sampling, four plants from each treatment were removed and
the leaf area for each plant was measured. Leafminers were reared
from the leaves at 24°C (18 hrs light: 6 hrs dark). Treatments
included water, 0.1% and 0.4% (aqueous, w/v) crude neem seed extract
made from concentrate (sample A13-42845 (AN 4.57); obtained from the
Biologically Active Natural Products Laboratory, ARS, Beltsville,
MD. Crude neem seed extract concentrate was made by extracting
seeds in 95% EtOH, drying the extract, and then resuspending the
extract in an equal weight of 95% EtOH. Crude neem seed extract
concentrate contained 2300 ppm azadirachtin, one of the insecticidal
principles in neem seed. Treatments also included 0.08% and 0.33%
(aqueous, v/v) Margosan-O (concentrate contained 3000 ppm
azadirachtin). We applied 15.6 liters of each treatment to the
assigned plot as a soil drench on each treatment date. Another plot
was sprayed on each treatment date with Trigard™ at a rate of

140.7 g Al/ha (0.125 1bs AI/acre). A last plot was treated by the
growers ("Grower" in Table 1) when they treated the rest of the
greenhouse. They sprayed irregularly with MavrikIM (Zoecon) and
Pramex!M (Penick) and applied Temik!M (Union Carbide) twice to

the soil, all at recommended rates.

Mean pupal and adult counts from plants sampled at week 6 are
given in Table 1. The data from week 6 are given because this was
when the largest mean number of adults were reared from the
water-treated plot. Only Trigard!M significantly reduced the mean
number of pupae compared to the water treatment. The mean number of
reared adults on week 6 was significantly lower in TrigardIM, 0.4%

crude neem seed extract, and 0.33% Margosan-O plots than with any
other plots. An indication of treatment effects through the season
is given by the total number of pupae and adults reared from all 20
plants harvested from each plot. Trigard,!M 0.4% crude neem seed
extract and 0.33% Margosan-O dramatically reduced the number of

reared adults. We felt that neither 0.1% crude neem seed extract or'

0.08% Margosan-O gave adequate control. No growth inhibition or
other signs of phytotoxicity were observed on any of the treated
plants.

Crude neem seed extract and Margosan-O did not protect the
crop's foliage from damage. A 0.4% solution of neem and 0.33%
solution of Margosan-0, however, greatly reduced the number of flies
reared from the treated crop. Thus, insecticidal constituents of
soil-applied crude neem seed extract and Margosan-O were taken up by
chrysanthemums, were fed upon by leafminer larvae, and caused
significant pupal death. The delay between time of application and
observed effect suggests that neem acts as an insect growth
regulator against L. trifolii. We are studying this possiblity.

We recommend that a commercial formulation of neem seed
extract such as Margosan-O be considered further for possible use on
chrysanthemums against L. trifolii.

Acknowledgements

Neem seed extract was provided by David Warthen, USDA,
Beltsville, MD. Robert Larson of Vikwood Ltd., Sheboygan, WI
donated the Margosan-O. Garry Se of Ciba-Geigy Corp.,
Greensboro, NC donated the Trigard.! George Rye and Howard Rye
in Perry Hall, MD let us use their commercial greenhouse for our
experiments. Maureen Gough provided technical assistance. This
project was funded in part by The Fred C. Gloeckner Foundation.

a A a a LE Fl Ue ae a tes Sh ee

Table 1: Results of Commercial Greenhouse Experiment

a a ETE TE SL

Mean Mean
Treatment Pupae Adults Totall Totall

(Wk 6) (Wk 6) Pupae Adults
Water 42be 32a 332 205
“Grower” 30c 23b 261 186
0.1% Neem 65a 14c 394 85
0.4% Neem 38be Usod 189 2
0.08% Margosan-0 48ab 33a 362 220
0.33% Margosan-0 55ab 3d 350 16
Trigard TM Od Od 4 ih

er meres cero ra ed LS

N = 4 plants/treatment. Means within a column are not significantly
different at K-ratio = 100 (5% level), Waller-Duncan K-ratio t test.

1 Total reared from all plants (20/treatment) sampled during
experiment.

Literature Cited

Gill ele Oe and Geel ehewlse meLo7ie Systemic action of an insect
feeding deterrent. Nature 232:402-403.

Jacobson, M. 1981. Neem research in the U.S. Department of
Agriculture: Chemical, biological and cultural aspects,
pp- 33-42. In H. Schmutterer, K. R. S. Ascher, and H. Rembold.
[eds.], Proc. lst Intl. Neem Conf., Rottach-Egern. German Agency
for Technical Cooperation (GTZ). Eschborn.

Larew, H. G., J. J. Knodel-Montz, R. E. Webb, and J. D. Warthen.
In press. Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)
controlled on chrysanthemum by neem seed extract applied to
soil. J. Econ. Entomol.

Price, J. F. 1984. Results of recent field experiments with
Trigard, Avid and other pesticides on flower crops in Florida.
pp- 139-150. In S. L. Poe [ed.], Proc. 4th Ann. Indus. Conf,
Leafminer, Sarasota, FL (Sponsored by the Growers Division,
SAF--The Center for Commercial Floriculture; Alexandria, VA).

Efficacy of Margosan-O, a formulation of neen,
against Liriomyza trifolii (Burgess) on floral crops

Janet J. Knodel-Montzt, Hiram G. Larewt, and Ralph E. Webbt

Abstract

Efficacy of soil-applied Margosan-O, a formulation of neem, was
evaluated against Liriomyza trifolii (Burgess) on four floral
crops: chrysanthemum, marigold, zinnia, and snapdragon. Leafminer
control varied depending on the floral crop treated. Concentrations
of 0.17% and 0.33% Margosan-O were efficacious in killing larvae and
pupae reared from chrysanthemums. The highest concentration of
Margosan-O (0.33%) also caused a significant decline in the number
of adults reared from marigolds. Reductions in the number of adults
reared from zinnias were not significant from control. Too few
adults emerged from snapdragons to make efficacy determinations.
Leafminers preferred chrysanthemums, marigolds, and zinnias for
stippling and oviposition over snapdragons.

Introduction

The botantical insecticide, neem, comes from a tropical tree
(Azadirachta indica A. Juss) grown primarily in the arid regions of
Asia and Africa (Radwanski 1977). The insecticidal property of neem
has been known for over 20 years It is believed to act as an insect
feeding inhibitor and/or growth regulator (Warthen 1979). Warthen
(1979) compiled a list of seven insect orders that are affected by
neem's insecticidal activity. Because neem appears to be a potent
natural insecticide and may offer an environmentally safe method of
insect control, a neem product called Margosan-02 has been
developed in the United States for commercial use on ornamentals.

Crude neem seed extracts applied as foliar sprays, soil
drenches and leaf dips have been found to be effective in
controlling the serious leafmining pest, Liriomyza trifolii
(Burgess) (Diptera: Agromyzidae) (Fagoonee and Toory 1984;

1. Florist and Nursery Crops Laboratory, BARC-East, B-470, USDA,
ARS, Beltsville, MD. 20705.

2. Submitted for EPA registration and for patent by Vikwood Ltd.,
Box 554, 1221A Superior Avenue, Sheboygan, WI. 53081.
Mention of a product does not constitute an endorsement by the

USDA.

Larew et al. 1984, in press; Webb et al. 1983, 1984). Liriomyza
trifolii is a polyphagous insect attacking a large array of floral
crops (Poe 1984). In 1981, this leafminer is estimated to have
caused $17 million in damages to the chrysanthemum industry of
California alone (Parrella and Jones 1984). The systemic uptake of
crude neem extracts has been demonstrated in chrysanthemums and
several agricultural crops (Gill and Lewis 1971; Larew et al. 1984,
in press; Webb et al. 1984). Since our preliminary studies have
shown Margosan-O to be taken up systemically (Knodel-Montz et al. in
preparation), we investigated whether soil-applied Margosan-0O
affected the survival of L. trifolii on four floral crops.

Materials and Methods

Leafminer colony

Chrysanthemums cv. Iceberg were used to rear Aiegb cL LOLs.
Chrysanthemums were grown singly in 10 cm plastic square pots in a
mixture of 50% Luna Rock!™M (Pennsylvanina Perlite Corp., LeHigh
Valley, PA) and 50% Promix!M (Premier Brand, Inc., New Rochelle,
NY). Plants were left unpinched and fertilized weekly with
20N:20P:20K. Chrysanthemums were grown in a greenhouse at 23-30°9C
until exposure to leafminers. The leafminer colony was maintained
at 24°C, with a long day photoperiod (16L:8D) at 5600 lux (high
pressure sodium lamps and incandescent bulbs).

Margosan-O

Margosan-O contains 3,000 ppm azadirachtin, one of the active
insecticidal components in neem (Warthen 1979). Dilutions of
Margosan-O were prepared with water as volume/volume solutions.

Chrysanthemum experiment

This experiment was conducted from 29 March to 11 May, 1984.
Chrysanthemums cv. Iceberg were treated with concentrations of
0.0083%, 0.083%, 0.17%, and 0.33% Margosan-O and water as control.
Each treatment contained five, 3-week old chrysanthemums grown from
cuttings. Each plant (pot) was drenched with 150 ml of its
treatment solutions resulting in slight drainage. Plants were
returned to the greenhouse for 3 days to allow for chemical uptake.
Plants were then placed randomly in the leafminer colony cage and
exposed to 75-100 leafminer adults for 24 hrs. After exposure,
plants were returned to the greenhouse and the number of first
instar mines (less than 1 cm in length) were counted (usually three
to four days later). When larvae matured (third instar), damaged

leaves longer than 2.5 cm (petiole and midvein) were removed, passed
through an area meter (Li-Cor, Inc., Lincoln, NE), and placed in
plastic meat trays. Trays were examined daily for crawling
prepupae. Prepupae were collected in gauzed-covered glass vials.
Vials were kept in an environmental chamber at 26°C, 14L:10D
photoperiod until adult eclosion. The numbers of pupae and adults
were counted. Densities of mines, pupae, and adults were calculated
on 100 cm* leaf area and comparisons between treatment plants and
different floral crops were made.

Marigold, zinnia, and snapdragon experiments

All three floral crops were purchased from a local nursery
(Beltsville, MD). The following cultivars were selected: marigold
cv. Honeycomb; zinnia cv. Thumbelina Mix; and snapdragon cv. Yellow
Rocket. Plants were transplanted into 10 cm square plastic pots
using the same potting medium as chrysanthemums. Treatment
concentrations and experimental procedures were identical to those
described in the chrysanthemum experiment. However, a sample size
of four plants per treatment was used, and the number of stipples
(in addition to mines, pupae, and adults) was counted. Time periods
were 8 June to 27 July for the marigold experiment; 18 June to 6
August for the zinnia experiment, and 14 June to 6 July for the
snapdragon experiment.

Statistical Analysis

Means of first instar mines, pupae, adults, and stipples were
analyzed by analysis of variance (ANOVA) and separated by the
Waller-Duncan K-ratio t-test at the K-ratio = 100 (5% level). Means
for the host plant preference study were analyzed using ANOVA and
Duncan's Multiple Range test (P = 0.05).

Results and Discussion

First instar mines

In Table 1, the mean number of first instar mines and mine
densities are shown for various concentrations of Margosan-O on all
four crops. There were no significant differences caused by the
various concentrations of Margosan-O for any of the crops. However,
the number of mines and mine densities decreased on chrysanthemums
at the higher concentrations. Other studies have shown no
deterrance of early larval development when crude neem seed extract
was applied to the soil (Larew et al. 1984, in press; Webb et al.
1984).

Pupae

The mean number of pupae and pupal densities for
chrysanthemums, marigolds, zinnias, and snapdragons at the various
concentrations of Margosan-O are illustrated in Table 2. For
chrysanthemums, concentrations of 0.17% and 0.33% Margosan-0O
significantly reduced the number of pupae and pupal densities
compared to water-treated chrysanthemums. Marigolds, zinnias, and
snapdragons had no significant differences in any treatments,
although the higher concentrations seemed to increase larval
mortality. Margosan-O effectively reduced the mean number of larvae
surviving to pupation on chrysanthemums, but not on marigolds,
zinnias, or snapdragons. This variability indicates that Margosan-0O
differed for these floral crops.

Adults

The mean number of adults and adult densities for various
concentrations of Margosan-O against L. trifolii on floral crops are
shown in Table 3. A concentration of 0.083%, 0.17%, and 0.33%
Margosan-O significantly reduced the mean number of adults reared
from chrysanthemums. All tested concentrations of Margosan-O
significantly decreased the mean adult densities on chrysanthemums.
For marigolds, the highest concentration of Margosan-0 significantly
decreased the mean number of adults and adult densities. No
significant differences were observed for any concentrations on
zinnias and snapdragons, although a 0.33% concentration on zinnias
had lower mean adult counts and densities. Again, Margosan-O seemed
to affect leafminer development differently depending on the floral
crop. Margosan-O was effective in decreasing the number of adult
leafminers reared from chrysanthemums and marigolds.

Stipples

The number of stipples was not counted for chrysanthemums.
Mean number of stipples and stipple densities for marigolds,
zinnias, and snapdragons are given in Table 4. No significant
differences in the number of stipples and stipple densities were
observed for zinnias and snapdragons. For marigolds, a
concentration of 0.17% Margosan-O0 resulted in a higher stipple count
than a concentration of 0.0083% Margosan-0, and a higher stipple
density than 0.083% Margosan-O and water. On all three bedding
crops, Margosan-O did not decrease the stippling (feeding and
ovipositional) activity of female leafminers. Larew et al. (1984, in
press) and Stein (1984) also observed that soil-applied crude neem
seed extract did not repel females from feeding or ovipositing.

Host Plant Preference

Comparisons of counts and densities of mines, pupae, adults and
stipples for water-treated floral crops are shown in Table 5.
Snapdragons had significantly lower counts and densities for all
variables compared to chrysanthemums and marigolds. Snapdragons had
significantly lower counts and densities from zinnias for the
following variables: mean number of mines, pupae, adults and
stipples, and mean pupal and adult densities. This suggests that
snapdragons were the least preferred host plant compared to
chrysanthemums, marigolds, and zinnias. Since stippling was
initially lower on snapdragons, the nonpreference probably caused an
effect on the later counts (mines, pupae, adults). Observations of
other cultivars of snapdragons have shown that certain cultivars are
heavily attacked by leafminers suggesting that the nonpreference
observed for snapdragons was a factor of cultivar selection by
leafminers.

Chrysanthemums, marigolds and zinnias were not significantly
different in regards to either counts on densities of pupae and
adults. This indicates that all three crops were equally good hosts
for leafminer development. Interestingly, significantly more
stippling on marigolds than zinnias did not yield significantly more
mines, pupae or adults. This suggests that female leafminers
preferred to feed on marigolds compared to zinnias, but showed no
preference for egg laying. Further host plant preference studies
need to be conducted to determine feeding and oviposition
preferences of host plants by leafminers.

Conclusion

In conclusion, the efficacy of Margosan-O is variable depending
on the floral crop treated. For example, a concentration of 0.33%
Margosan-O was effective in killing leafminer pupae reared from
chrysanthemums and marigolds, but not from zinnias or snapdragons.
This was probably due to differential uptake of the product by the
crops. When effective, Margosan-O appeared to prevent the larval
and pupal stages from surviving. According to Larew et al. (1984,
in press) and Webb et al. (1984), a 0.1% or higher concentration of
crude neem seed extract applied to the soil of chrysanthemums
resulted in significant larval and pupal mortality. Margosan-0O has
chemical control potential for leafminers; however, the variability
of effects on different floral crops needs to be considered.
Applying higher concentrations that are not phytotoxic or using
different application techniques (i.e. foliar spray vs. soil drench)
or varying the soil type (Webb et al. 1984) could overcome the
problem of differential efficacy of Margosan-O on floral crops.

Acknowledgements

Authors are grateful to Robert 0. Larson, for providing the
Margosan-O, and Yoder Bros., Inc. of Florida for providing the
chrysanthemums. Technical assistance was provided by Rhonda Borisko
and Maureen Gough. We sincerely thank The Fred C. Gloeckner
Foundation for supporting this project.

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Literature Cited

Fagoonee, I. and V. Toory. 1984. Contribution to the study of the
biology and ecology of the leaf-miner Liriomyza trifolii and its
control by neem. Insect Sci. Appl. 5: 23-30.

Gill, J.S. and C.T. Lewis. 1971. Systemic action of an insect
feeding deterrent. Nature 232: 402-403.

Larew, H.G., J.J. Knodel—Montz, R.E. Webb, and J.D. Warthen. In
press. Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)
controlled on chrysanthemums by neem seed extract applied to
soil. J. Econ. Entomol. #78.

Larew, H.G., R.E. Webb and J.D. Warthen. 1984. Leafminer controlled
on chrysanthemum by neem seed extract applied to potting soil.
pp. 108-117 In: S.L. Poe (ed.), 1984, Proc. 4th Ann. Ind. Conf.
Leafminer, Jan. 16-18, Sarasota, FL. 191 pp.

Parrella, M.P. and V.P. Jones. 1984. Coping with the ‘leafminer
crisis’. .Calit mAgric.. 06: o1/—-19.,

Poe, S.L. (editor). 1984. Proc. 4th Ann. Ind. Conf. on the leafminer.
Jan. 16-18, Sarasota, FL. 191 pp.

Radwanski, S. 1977. Neem tree 1: Commercial potential
characteristics and distribution. World Crops & Livestock 29:
62-007, 05-00.

Stein, U. 1984. The potential of neem for inclusion in a pest
management program for control of Liriomyza trifolii on
chrysanthemum. M.S. Thesis, Univ. CA., Riverside, 86 pp.

Warthen, J.D. 1979. Azadirachta indica: a source of insect feeding
inhibitors and growth regulators. U.S.D.A. Agric. Rev. Man.
ARM-NE-4, 21 pp.

Webb, R.E., M.A. Hinebaugh, R.K. Lindquist and M. Jacobson. 1983.
Evaluation of aqueous solution of neem seed extract against
Liriomyza sativae and L. trifolii (Diptera: Agromyzidae). J.
Econ un tomol.1.6 so G-002.

Webb, R.E., H.G. Larew, A.M. Weiber, P.W. Ford and J.D. Warthen.
1984. Systemic activity of neem seed extract and purified
azadirachtin against Liriomyza leafminers. pp. 118-128 In S.L.
Poe (ed.), 1984, Proc. 4th Ann. Ind. Conf. Leafminer, Jan.
16-18, Sarasotay kG. 190 pp.

Effects of Cyromazine (Trigard™) on
Liriomyza trifolii (Burgess)

Gary L. Leibee!
Abstract

A bioassay procedure was developed to evaluate the dosage-mortal ity
response of Liriomyza trifolii (Burgess) to cyromazine using infested
cowpea, Vigna sinensis, plants. The LDs5g and LDgp values for the larval
stage were 6 ppm and 15 ppm, respectively. The number of deformed
puparia developing from surviving larvae increased with dosage. A
decrease in adult eclosion was associated with deformity of the puparia.
Nine out of 14 generations of L. trifolii larvae were subjected to LDs5o
(6 ppm) pressure with cyromazine. LD and LD 9 values indicated that
no resistance had developed.

Introduction

Cyromazine, the active ingredient in Trigara™ (Ciba-Geigy), is a
very effective development inhibitor against Liriomyza trifolii (Burgess).
Cyromazine has had limited use on celery for leafminer control. Ciba-
Geigy is pursuing full registration for the use of cyromazine on a
variety of crops. Since Liriomyza leafminers have a history of develop-
ing resistance to insecticides dates! 1981), it would be valuable to
develop base-line data on the dosage-response relationship of L. trifolii
to cyromazine to monitor populations for resistance after widespread use
of cyromazine occurs.

This project was conducted to: (1) develop a relatively easy
method of bioassaying insecticides against L. trifolii larvae, (2)
generate base-line data for Trigard against L. trifolii, and (3) use
these data and methods to attempt to select for cyromazine resistance in

Petri folit.
Methods and Materials

Dosage-Response. 'California blackeye' cowpeas, Vigna sinensis,
were seeded in vegetable plug mix in bedding plant trays (Com-Packs,

Model D812, T. 0. Plastics, Inc.) and maintained at 25°C until the primary
leaves were fully developed (approx. 7 days). These plants were placed
into infestation cages containing newly emerged L. trifolii adults. The
number of adults used varied due to availability. The plants were

removed 24 to 48 hours later depending on the number of stipples present.
A 48-hour maximum time of exposure to the adults was used to avoid
hatching of the eggs before exposure to the insecticide.

‘Univ. of Florida, Institute of Food and Agricultural Sciences, Central

Florida Research and Education Center, P. 0. Box 909, Sanford, FL
Cr AL:

Solutions of cyromazine for dipping the plants were Prepared from a
40 ppm stock solution of cyromazine made from 0.16 gram of Trigard 75 WP
and 3000 ml of distilled water. The appropriate amounts of stock solution
were diluted to 1800 ml to prepare 2, 4, 6, 8, 10, 12, and 14 ppm
solutions of cyromazine. A wetting agent, 0.63 ml/1 of X-77 (Chevron
Chemical Co.), was added to the solutions to promote wetting of the
cowpea leaves. A solution of distilled water and X-77 alone was used
for the untreated check.

Each infested plant was removed from the plant tray, the leaves and
part of the stem submersed for 5 seconds in the solution, and returned
to the same plant tray. Ten plants were used for each dosage. The
treated plants were maintained at 25°C until it was evident that larvae
were about to exit the leaves. At this time, the leaves were excised
and the leafmines counted. The leaves were then placed in plastic Petri
dishes lined with filter paper and sealed with Parafilm(R) to prevent
the leaves from drying out. After 7 days at 25°C, the pupae were
retrieved and placed in plastic pill cups. The pupae were maintained at
25°C for 2 weeks to allow the adults to emerge and die. The puparia
were examined and classified according to morphology as either normal,
larviform, or otherwise abnormal. Adult emergence was recorded for each
morphological type. Larval survival was calculated by dividing the
total number of puparia (all morphological types) collected from a plant
by the total number of leafmines it had contained. Abbott's formula was
used to correct for mortality in the untreated check.

Resistance Study. Liriomyza trifolii adults reared from infested

carrot foliage collected from a commercial vegetable farm in Zellwood,
FL, were divided into two populations; one population to be selected at
the LD59 level and the other population to serve as an unselected check.
The selected population was exposed to cyromazine by placing the adults
in an infestation cage containing cowpea plants that had been dipped in

6 ppm of cyromazine as described Previously. Undipped plants were used
in the infestation cage for the unselected populations. The plants were
replaced every 2-4 days until there were very few stipples present on

the leaves. After the last plants were removed, the cages were cleaned
thoroughly to remove the flies. The plants were maintained as previously
described. When the larvae were about to exit the leaves, the leaves
were excised and placed onto 6.5 mm wire cloth TN? 22E9AX937 1X10. 58m
deep, polystyrene boxes with lids (No. T295C, Tri-State Molded Plastics,
Dixon, Kentucky). ‘The bottoms of these boxes were lined with paper
towels (No. 227, Veltex Singlefold Towels, Fort Howard Paper Co., Green
Bay, Wisconsin) to absorb excess moisture to prevent the larvae from
drowning. The pupae were retrieved from the boxes daily and placed into
plastic pill cups. The pupae were stored at 10°C to arrest development
until all the pupae from a generation were collected. All the pupae

were then transferred to 25°C to allow development to the adult Stage.
All the adults were then introduced back into the infestation cage to
repeat the procedure for the next generation. If the number of adults
from a generation was low enough to endanger survival to the next
generation, the selection process was Skipped (leaves were not dipped in
cyromazine) to remove deteterious effects of the cyromazine and allow the
number of adults to increase to a level that insured survival to the next
generation and still allowed selection.

Results and Discussion

Dosage-Response. Larval survival decreased with increasing
cyromazine concentration as expected (Table 1). The LDs5g and LDgg were
6 and 15 ppm, respectively. The dosage-mortality response occurred over
a low and narrow range of concentrations (0-14 ppm) relative to the field
rate of 300 ppm recommended for leafminer control on celery. This
difference in the level of activity is not unexpected due to the inherent
differences of these two systems, such as, plant species, application
techniques, environmental conditions,and insect pressure.

The number of larviform and otherwise abnormally shaped puparia
tended to increase with dosage (Table 2). There was a 5.8-fold increase
in deformed (larviform + abnormal) puparia from 4 ppm to 6 ppm. Within
each shape category there was no significant (P > .05) difference in
adult eclosion due to dosage. A decrease in adult eclosion was associated
with deformity. The mean percent adult eclosion + SE over all dosages for
each shape: category was 793.5 tole S,gloscen 4.7, and 52.5:+05325for. the
normal, larviform, and abnormal puparia, respectively.

Resistance Study. Nine generations out of 14 were subjected to
LDsg (6 ppm) pressure. F 3, 5, 6, 10, and 12 were not subjected to
pressure because the number of adults from the preceding generation was
considered too low to provide enough larvae to subject to pressure and
still insure survival to the next generation. Examination of the LDs5o
and? LOgq values fonvFlso. 934] 4s"and lo sfor thesselected and tunselected
populations (Table 3) indicate that resistance had not developed.

Table 1. Dosage related survival of L. trifolii larvae in cowpea
leaves dipped in cyromazine.

ppm of cyromazine
0 2 4 6 8 10 NZ 14
% larval :
mOCtal i ty oo, C cay to 0 ot! 71.0 feeeos eo DC a3 eeaecd. 33.0.d UshbuS ie: 9.0 e

@Means followed by the same letter are not significantly different

(P < 0.05; Duncan's [1955] new multiple range test). ANOVA performed
on transformed (sine-!/x) data.

Table 2. Percent composition of puparia shapes resulting from ic,
trifolii larvae exposed to different levels of cyromazine.

pm of

p
cyromazine Normal Larviform Abnormal
a

0 98.6 a 02056 lv4e
a 97.0 a Os08e 3.0 e
4 90.6 a 2.8 be 6.5 de
6 5Oa0RD 21.5 ab 22. 5a
8 29/4 bc 255904 44.7 be
10 2 ae 23.2 ab 64.1 ab
12 Paw sae 16.1 abc 62.3 ab
14 Lae4ec 7.9 abc 1/7 ima

oMeans followed by the same letter in each column are not Significantly
different (P < 0.05; Duncan's [1955] new multiple range test). ANOVA
performed on transformed (sine-!/x) data.

Table 3. Responses to cyromazine of a population of L. trifolii
subjected to LDsq pressure by cyromazine compared to an unselected popu-
lation from the same parental stock.

Unselected Selected

: a,b a,b aes a,b
Generation LD LDgo LDE 9 LDgo
Santa ee ge ere OUR Me Wee One O te

] Jae 1520 -- --
8 7.0 24.0 ewe Z0S0
9 6y2 13.5 4.0 9.4
14 43 9.0 4.3 120
15 bag 11.0 Os2 14.0
a

ppm

Biades are estimates determined from line fitted by eye to data plotted
On log-probit paper.
Literature Cited

Leibee, G. L. 1981. Insecticidal control of Liriomyza spp. on vegetables,

pp. 216-220. In D. J. Schuster [ed.], Proc. IFAS-Ind. Conf. Biol.
Control Liriomyza Leafminers. II. Lake Buena Vista, FL.

Response of Liriomyza trifolii to Twospotted Spider Mites
and Their Damage on Chrysanthemum

HR
James F. Price and Cheryl Roesel

Abstract. Twospotted spider mites (Tetranychus urticae
Koch) colonize and feed upon the lower surfaces of
chrysanthemum (Chrysanthemum X morifolium Ramat.) leaves.
Their activity on upper surfaces of leaves is minimal except
alter populations sinenease greatly: j.lnacontrast,,adult
Liriomyza trifolii (Burgess) leafminers feed and oviposit in
upper surfaces of chrysanthemum leaves and leafminer larvae
develop there. Even though the two species largely occupy
different leaf surfaces of the plant previous research data
indicated that leafmining increased in chrysanthemum when
twospotted spider mites were restricted to low densities by
Mebec ides. hoses studtes indicated hat activities of
leafminer parasitoids were not reduced by the miticides and
had no effect on the increased leafmining. This study was to
determine if the twospotted spider mite or its effects on
leaves could result in reductions in leafminer
feeding/oviposition punctures and mining in chrysanthemum,

In experiment 1, 5 treatments were applied to plots in 6
randomized complete blocks. Treatments were O, 5, 10, 15 or
20 adult, female, twospotted spider mites placed on the lower
surface of each of 3 leaves on one ‘Manatee Iceberg'
chrysanthemum plant. After 5 days of mite infestation the
plants Wwene wut into a cage Tor) ) day to permit leafminer
flies to feed and lay eggs. Five days later the numbers of
feeding/oviposition punctures and mines were counted. In
Experiment 2, four treatments in 12 randomized complete
blocks were included. Experimental units were 'Manatee
Iceberg’ chrysanthemum plants with all but 2 leaves removed.
Fifteen adult, female, spider mites were placed on each of 2
leaves of plants in 2 of the treatments. Plants for’ the
other 2 treatments were not infested at that time. Four days
later leaves from one of the treatments infested were washed
thoroughly to remove mites and their eggs; 15 adult, female
spider mites then were applied to 2 leaves of plants in one
of the previously uninfested treatments. All plants
subsequently were exposed to adult leafminers for 1 day.
Resulting oviposition/feeding marks and leafmines were
counted 5 days later.

University of Florida, IPAS; GultsGoast’ Research and
Education Center, Bradenton, §FlL.9°34203) and New College,
Department of Natural Sciences, Sarasota, FL, 34243
Tespectively. Orvionse wor tnt ouctidyewere performed as an
independent research project of the junior author.

In Experiment 1 numbers of feeding/oviposition marks and
numbers of mines were greatly reduced when 5 mites were
applied to leaves; further reductions in punctures and mines
occurred from additional increments of nites.” lr olxpertment
2, the highest numbers of punctures and leafmines occurred
when no mites had been applied to the leaves or when mites
were applied on the day chrysanthemums were introduced to
adult flies. Large reductions in punctures and mines were
evident when mites were allowed to develop on leaves for 5
days, both when mites were removed by washing or when they
remained on the” leavees

These data Support field observations that Colonuzarion
of chrysanthemum leaves by twospotted spider mites reduces
leafminer oviposition/feeding puncturing and subsequent
mining. These data further indicate that these biological
parameters are affected by leaf conditions caused by spider

mites and not simply the presence of spider mites on the
leaves.

The Comparative Responses of the Vegetable Leafminer, Liriomyza
sativae (Blanchard) (Diptera: Agromyzidae) and the Greenhouse
Whitefly, Trialeurodes vaporariorum (Westwood)
(Homoptera: Aleyrodidae), to Visual Stimuli.

Ralph E. Webb,+ Floyd F. Smith,! Anne M. Wieber,2
Hiram Larew 11,1 and J. J. Knodel-Montz?

Abstract

The responses of the vegetable leafminer, Liriomyza sativae
(Blanchard) (VLM), and the greenhouse whitefly, Trialeurodes
vaporariorum (Westwood) (GHWF), to sticky yellow boards placed in
various arrays in a greenhouse were compared in a series of 11 studies
at Beltsville, MD and Baltimore, MD. Study 1 demonstrated, that for
both L. sativae and a closely related serpentine leafminer, L. trifolii
(Burgess), males and females were equally attracted to sticky yellow
boards. Study 2 showed that there was a pronounced tendency for adult
female L. trifolii to be caught on yellow sticky monitoring cards placed
among a crop of chrysanthemums in a commercial greenhouse in Baltimore,
MD. In Study 3, GHWF was influenced by board size by a factor greater
than unity, while VLM landed in similar numbers on all boards,
apparently ignoring board size. Study 4 demonstrated that proximity to
the point-of-release was even more important than relative board size
for GHWF. In contrast, VLM ignored both board size and distance from
the release site in choosing a landing site. In Studies 5-10, GHWF
preferred vertical to horizontal boards, while VLM generally preferred
horizontal boards, apparently preferring a thin edge to a large area.
Again, GHWF always preferred larger areas to smaller ones, and nearer
objects to more distant ones, while VLM was unaffected by these
parameters. VIM preferred to fly outwards rather than downwards from
the point-of-release. GHWF always went preferentially to the object
that would be perceived as larger when viewed from the point-of-release,
and would readily fly downward if a lower board was perceived as being
larger than an upper board. In Study 11, when boards were placed
vertically or at 60° or 45° angles, at various heights, GHWF went
preferentially to that board perceived as being larger from the
perspective of the release point, while the VLM always preferred the
45° board to the 60° one, and the 60° board to the vertical,

I Florist & Nursery Crops Laboratory, Bldg. 470, BARC-East, USDA,
Beltsville, MD 20705.

é Maryland Department of Agriculture, 50 Harry S. Truman Parkway,
Annapolis, MD 21401.

3 Department of Entomology, University of Maryland, College Park,
MD 20742.

ou!

regardless of height of placement. In summary, GHWF responded very
differently, often exactly the opposite, than did VLM to arrays of
yellow sticky boards. The practical significance of these results is
that, when attempting to improve catch of GHWF, both board area and
proximity to the infestation should be maximized. When attempting to
maximize catch of VLM, small yellow cards should be distributed at
many locations throughout the greenhouse, or, thin sticky tapes should
be strung down the middle of the greenhouse bench or bed, just above
the level of the canopy.

Previous work at Beltsville, MD (Affeldt et al. 1983) determined
the phototactic sensitivity level of the greenhouse whitefly (GHWF)
(Trialeurodes vaporariorum (Westwood)) and the vegetable leafminer
(VIM) (Liriomyza sativae (Blanchard)) to six series of color
pigments. Results demonstrated that maximum response of both species
occurred in the yellow-green region of 500- to 600-nm, and that
capture of both species was inhibited by blue light energy from 400 to
490 nm. Generally, GHWF responded strongly to 5- to 10-nm shifts of
spectra in the critical range of 510- to 540-nm, whereas VLM response
to such shifts, while similar, was not strong enough to be
statistically significant. The present study continues the analysis
of the comparative visual behavior of these 2 species by comparing and
contrasting their responses to yellow boards of varying size placed at
varying distance from the point of release, and by varying the height
of the boards and the position of the boards, as well as the angle of
the boards, relative to the point of release. A second issue resolved
is whether there are differences between sexes in the visual response
of 2 leafminer species, L. sativae and L. trifolii (Burgess).

Methods and Materials

General Methods. All boards used in this study, unless otherwise
specified, were made of Almac Yellow Plastic 2037 (Almac Plastics of
Maryland, Inc., Baltimore, MD), the reflectance spectrum of which is
given in Affeldt et al. (1983). This was the most attractive surface
for both leafminers and whiteflies evaluated in that study. All
boards were coated with Tack Trap® (Animal Repellents, Her oeyy

Griffin, GA). The study was conducted in a 45-m2 greenhouse, on the
center bench of which 2 rings were established around a central
release point (Fig. 1). The inner ring was 77-cm in diameter while
the outer ring was 154-cm in diameter. Each ring was divided into 4
quadrants. The experimental design was a randomized block with 4
blocks with boards positioned in a repeated pattern in each block.
The correct height, position, and angle of the boards was achieved
either by suspending the boards from a plastic ring as per Affeldt et
al. (1983), or by using ring stands. Adult whiteflies and adult
leafminers were collected in the same glass vial by aspiration
techniques, and this vial was placed into a 3.8-1 widemouth glass
bottle placed on a ring stand so that the top of the bottle, which was
considered the actual release point, was 76-cm above the surface of

the bench (see Affeldt et al. 1983 for illustration). Thus the
whiteflies and the leafminers were released simultaneously. The lid
to the widemouth jar was suspended 8-cm directly above the top of the
jar in order to orient them toward the trap array by preventing them
from billowing straight upwards.

Studies 1 and 2. Sex-Ratio Studies. The studies reported here assume
that male and female leafminer adults exhibit a similar response to
visual stimuli. We tested this assumption in 2 ways. First, we
released known numbers of each sex from our central release point.
After 24-h we counted the numbers of each sex captured on a 30.6 x
30.6 x .3-cm board placed in each quadrant of the inner ring (at
Position A in Fig. 1). We also mapped the position of each insect
captured. In these trials, the release point was 60-cm above the
bench while the top of the boards was 76-cm above the bench. There
were 4 trials, 2 each for L. sativae and L. trifolii. Secondly, we
evaluated the sex ratio found on sticky cards that had been placed at
weekly intervals in a commercial chrysanthemum greenhouse to monitor
L. trifolii populations. We evaluated 3 cards from each of 10 dates
beginning March 8, 1984 and ending October 9, 1984. This permitted us
to ascertain whether response to yellow boards varied in either sex by
season. The monitoring cards used were 14.5 x 30.8-cm commercial
sticky traps produced by Olson Products, Inc., Medina, OH.

Study oe Comparative response of GHWF and VLM to Board Size. GHWF

and VLM adults were released into an array consisting of 4 sizes of
sticky panels, including 3 Almac boards 30.6 x 30.6 x 0.3-cm, 20.4 x
20.4 x 0.3-cm, and 10.2 x 10.2 x 0.3-cm, and an irregularly shaped
commercial stake ("Sticky Bars,” Reuter Laboratories, Inc., Haymarket,
VA) circa 20 x 4 x 0.1-cm (73-cm2 actual area). The yellow of the
Reuter stake was virtually identical to that of the Almac boards. The
boards were randomized for each quadrant of the outer circle, and
placed at the 4 points C, D, E, and F in Fig. 1. The release point in
this and all subsequent experiments was 76-cm above the bench. The
experiment was run twice. Statistical analysis was done using the
General Linear Models Procedure whereby linear regression for board
size against % capture was computed for each species, and the
significance of difference between the 2 regression coefficients was
determined by means of ‘the t-test. In this and all subsequent studies
percentages were converted to angles using the arcsine transformation.

Study 4. Effect of Interceptor Board Size and Relative Distance from

the Release Point on the Degree of Protection Provided for a Target
Board against GHWF and VLM. In this experiment an “interceptor” board

was placed (on Point A in Fig. 1) between the release point and a
second, “target” board (placed on Point B in Fig. 1). The target
board was always the 20.4 x 20.4-cm board used in the previous study,
while the interceptor board was either the 10.2 x 10.2-cm (Case 3),
the 20.4 x 20.4-cm (Case 1), or the 30.6 x 30.6-cm (Case 2) boards
used in the previous study. Thus the interceptor board had either
greater, equal, or less attractive surface than the target board. One
such board-pair was placed in each quadrant for each trial, and there
were 2 trials for each type of pairing. GHWF and VLM adults were

simultaneously released into the center of the array for each trial as
in the previous experiment, and we recorded their subsequent capture
on the board 24-h after release. After weighting our data to
eliminate directional effects, we compared our observed data for each
individual species, using the Chi-Square Test, against theoretical
values based on the following assumptions: A) That size and distance
had no effect on capture; that is, there should be a 50:50
distribution on the boards on the inner and outer ring. B) That
relative board catch is proportional to board size; therefore,

% Capture on Inner Board = ah a, ee il (Formula 1),
XO XO

and @Capture on Outer Board = 4} /2 SM Fy (Formula 2),
XO

where xi = area of the inner board and xo = area of the outer board.

C) That relative board catch is based on relative distance from the
release point; therefore,

do /do + 1
di di

% Capture on Inner Board (Formula 3)

and

(Formula 4),

4 Capture on Outer Board = 1/9 Lo ae

di
where do = distance of the outer board, and di = distance of the inner
board, from the release point.

D) That relative board catch is equally influenced by board size and
relative distance from release point; therefore,

% Capture on Inner Board -#) ayes (a2) + 1 (Formula 5),

KO \di oy) Walak)
and
% Capture on Outer Board = i (8) - (20) neal (Formula 6),
xO: i)

where xi, xo, di, and do are as above.

E) The same as Assumption D, but the effect of distance is squared;
therefore,

Aa, 104/ uae
4 Capture on Inner Board Tesh es ee ieg (Formula 7),
\x0} \di// \xo i/

and
Ree d b
% Capture in Outer Board = ] (2): (de) ahve (Formula 8),

where xi, xo, di, do are as above, and b = 2.

F) The same as Assumption D, but the effect of distance is taken to
the fourth power; therefore,

Formula 9 is the same as Formula 7,
and
Formula 10 is the same as Formula 8, except that b = 4.

G) This assumption is the same as assumption F except that it provides

a modest increase in the importance of relative board area by raising
relative area by a power of 1.4; therefore:

; Dye:
4 Capture of Inner Board +) Ves (20h, 1 (Formula 11),
fo) di fo) di,

a
% Capture of Outer Board = (=) : (204

and

- it (Formula 12),
xO di

where xi, xo, di, do are as above, a = 1.4 and b

Studies 5-8. Effect of Vertical versus Horizontal Placement. We
conducted a series of 4 experiments (Studies 5-8) comparing horizontal
versus vertical placement of target boards. In study 5, the boards
were placed either horizontal or vertical to the point of release, and
were alternated along the inner circle (Points A and G in Fig. 1).

The horizontal board was placed level with the bottom edge of the
vertical board; that is, 56-cm from the surface of the bench. Study 6
was similar to Study 5, except that a second vertical board was hung
at the same height as the first on the outer circle (at Point H in
Fig. 1). Study 7 was the same as Study 5 except that the vertical
board was moved from the inner circle to the outer circle (to Point B
in Fig. 1), with the horizontal board left at Point G. Study 8 was
similar to the other 3 studies in this series except that a vertical
board was suspended at Point A 76-cm above bench level, a horizontal
board was placed at Point A 15-cm above bench level, and a horizontal
board was placed at Point B on the outer circle, also 15-cm above
bench level.

All target boards used in these 4 studies were the 20.4 x 20.4-cm
boards used in Studies 3 and 4, and adult GHWF and VLM were released
as above. There were 2 trials for each study. Each array was
repeated in each quadrant for each trial in each study.

We initially ran a 2-way ANOVA for all 3 studies with "species" as
one factor and “position” as a second factor. However, for all 3
studies we obtained a significant species x position interaction.
Therefore, for each study, we ran a l-way ANOVA for each species to
determine the significance of position, and paired t-tests to compared
the 2 species at each position.

Study 9. Horizontal Boards Placed at 3 Heights. Three 20.4 x 20.4
x .3-cm Almac Plastic 2037 yellow boards were placed horizontal to the

release point on a pole, one above the other, at 3 heights: 25-, 51-,
and 76-cm. One such pole was placed (at Point B on the outer circle
in Fig. 1) in each of the 4 quadrants. As in the preceding studies,

oy)

adult GHWF and VLM were simultaneously released from a central release
point that was 76-cm above the bench. There were 2 trials, so results
are based on counts of 8 boards at each height. To determine whether
the distribution of capture of the 2 species on the boards were
different, statistical analysis was done using the General Linear
Regression Models Procedure where by linear regression for board
height against % capture was computed for each species, and the
significance of difference between the 2 regression coefficients was
determined by means of the t-test.

Study 10. Boards Placed at 45° Angle to the Release Point at 3
Heights. Study 10 was identical to Study 9 except that the horizontal
boards of Study 9 were rotated 45° with respect to the release point.

Study 11. The Effect of Board Angle on the Ca ture of adult GHWF and
VLM, at 3 Heights. Study 11 was a set of 3 experiments in which 20.4
x 20.4 x .3-cm Almac Plastic 2037 yellow boards were placed on poles
at 3 angles relative to the release point: 90°, 60°, and 45°.

One board was placed per pole. The boards were randomized for each
quadrant of the outer circle, and placed at the 3 points H, I, and J
in Fig. 1. The first experiment in Study 11 was done with the center
(pivot line) of the boards at 76-cm. In the second experiment the
boards were placed at 5l-cm, and in the third experiment, the boards
were placed at 25-cm. As in the preceding studies, adult GHWF and VLM
were simultaneously released from a central release point that was
76-cm above the bench. There were 8 trials at the 76-cm height, and 4
trials at the 5l-and 25-cm heights, so that results represent totals
for 32, 16, and 16 boards for each angle at the respective heights.

Each experiment was statistically analyzed using the General
Linear Regression Model whereby linear regression for board angle
against % capture was computed for each species, and the significance
of difference between the 2 regression coefficients was determined by
means of the t-test.

Results

Sex Ratio Study 1. As seen in Table 1, most adult leafminers of both
sexes for both species were caught within 24-h of release. There was
no sign of a sex bias for capture for either species.

Sex Ratio Study 2. As seen in Table 2, there was no consistent trend
for a sexual bias in the numbers of adult L. trifolii caught on
monitoring yellow cards taken from a natural population infesting a
commercial chrysanthemum greenhouse near Baltimore, Maryland.
Although more females than males were trapped on most dates, we feel
that this may well reflect actual population trends in the
greenhouse. Significantly more females than males were caught during
4 of 10 trapping periods.

Study 3% Comparative Response of GHWF and VLM to Board Size. As seen

in Fig. 2, GHWF adults responded to the largest board more strongly
than would be expected based on its relative area in the array. GHWF
showed decreasing response to board size as board size decreased.
Conversely, VLM adults responded less than expected to large boards
and more than expected to small boards. Linear regression of board
size against % capture yielded a regression equation of y = — 18.5x
+ 72.0 with a regression coefficient of 3.6 for GHWF, and Vat S3u2x
+ 37.8 with a regression coefficient of 1.1 for VLM. These regression
coefficients were significantly different at the 1% level using the
t-test, indicating a significant difference in response of the 2
species to board size.

Study 4. Effect of Relative Board Size and Relative Distance from
Release Point on the Degree of Protection Provided for a Target Board
against GHWF and VLM. Results of Study 4 are given in Fig. 3. Adult
VLM's distributed themselves in a much different pattern than did GHWF
adults. Percent VLM adults landing on inner versus outer boards were
51:49; 51:49, and 54:46, respectively, for Cases 1, 2, and 3. In all
3 cases, these results were not significantly different by Chi-Square
Analysis from the 50:50 results expected from Assumption A. Thus, VLM
adults seemingly ignored both board size and relative distance from
release point under the conditions of this study. On the other hand,
observed catch of adult GHWF on inner versus outer boards was 94:6,
98:2, and 69:31 for Cases 1, 2, and 3, respectively. Obviously, both
board size and distance from release point affected % board catch of
GHWF. The relative importance of these 2 factors can be deduced by
comparing the observed pattern of capture with expected captures based
on Assumptions B-G. Assumption B was that relative board size was the
only important factor. Using Formulas 1 and 2, this assumption
predicted inner:outer board catches of 50:50, 69:31, and 20:80 for
Cases 1, 2, and 3, respectively. Clearly, Assumption B was wrong.
Assumption C was that expected board catch was proportional to the
distance from the release point. Since board size was ignored and the
relative distance from the release point was 2 for all 3 Cases used in
this study, the expected ratios, based on Formulas 3 and 4, would
always be 67:33. While this was closer to observed values than
Assumption B, and was a plausible fit for Case 3, Assumption C was
obviously not the entire story. Assumption D was that relative board
catch was equally influenced by board size and relative distance from
the release point. Expected ratios calculated from Formulas 5 and 6
were 67:33, 82:18, and 33:67 for Cases 1-3, respectively. Again,
Assumption D did not agree with observed results. Assumption E was
the same as Assumption D, except that the role of distance was
emphasized by squaring this factor. Using Formulas 7 and 8, ratios of
80:20, 90:10, and 50:50 were calculated for Cases 1-3, respectively.
While still fairly distant from observed results, Assumption E seemed
to be heading in the right direction. Assumption F increased the role
of distance still more by raising this factor to the fourth power.
Using Formulas 9 and 10, we calculated ratios of 94:6, 97:3, and 80:20
for Cases 1-3, respectively. While quite close to observed values, we

et)

felt we needed to increase the influence of board size, especially
since Study 3 had demonstrated that the influence of board size was
greater than unity. We found that modifying Assumption F by raising
the influence of area to the 1.4 power (Assumption G) resulted, using
Formulas 11 and 12, in calculated ratios of 94:6, 98:2, and 70:30.
This was similar to observed values in all 3 cases, and for the first
2 cases, were statistically in agreement by Chi-Square Analysis.

Studies 5-8. Effect of Vertical versus Horizontal Placement. Results
of Study 5 are given in Fig. 4 A. Distribution of GHWF adults on the
horizontal versus the vertical boards were 95:5 in favor of the
vertical. On the other hand, VLM adults distributed themselves 59:41
in favor of the horizontal. Results of a 2-way ANOVA test for GHWF
versus VLM as one factor and horizontal versus vertical placement as a
second factor gave a highly significant interaction for insect x
position, indicating that GHWF adults responded to the board array
differently than did the VLM. When 1-way ANOVA's were run
independently for GHWF and for VLM, the GHWF preference for the
vertical was significant at the 1% level while the VIM preference for
the horizontal was significant at the 5% level. Paired t-tests run
independently for the vertical and for the horizontal board positions
showed that the means of the GHWF and the VLM were significantly
different at the 1% level for both board positions, another indication
that the 2 species responded differently to the array.

Results of Study 6 are given in Fig. 4 B. Percentages of GHWF
adults landing on the 3 board positions (inner horizontal: inner
vertical: outer vertical) were 1:96:3, while results for VIM results
were 45:30:25. Again, GHWF showed a strong preference for the
vertical board over the horizontal, and the inner vertical board over
the outer vertical board, and again, VIM showed a preference for the
horizontal board over the vertical board, but little preference for
the inner vertical board over the outer vertical board. Results of a
2-way ANOVA test for GHWF versus VLM as one factor and the 3 board
placement positions as the second factor gave a highly significant
interaction for insect x position, once again indicating that GHWF
adults responded to the board array differently than did the VIM
adults. When l-way ANOVA's were run independently for GHWF and for
VLM, positional effects were significant at the 1% level for GHWF and
at the 54 level for VIM. Paired t-tests run independently for all 3
board positionings showed that capture means of the GHWF and the VIM
were different at the 1% level for all 3 positionings, again
indicating that the 2 species responded differently to this array.

Results of Study 7 are given in Fig. 4 C. Distribution of GHWF
adults on the inner horizontal boards compared to the outer vertical
boards were 87:13 in favor of the inner horizontal position. The VLM
adults also favored the inner horizontal boards, but by a less
pronounced ratio of 58:42. However, 2-way ANOVA still gave a
significant insect x position interaction, indicating that the 2
species did not respond to the array exactly the same way. When 1l-way
ANOVA's were run independently for GHWF and VLM, positional effects
were significant at the 14 level for GHWF but non-significant for

VIM. Paired t-tests run independently for both positionings were
non-significant for % species captured for either board positioning.

Results for Study 8 are given in Fig. 4 D. Percentages of GHWF
adults landing on the 3 board positions (inner vertical-high, inner
horizontal-low, outer horizontal-low) were 79:18:3 for GHWF and
65:15:20 for VLM. Although the response to this array was very
similar for the 2 species, enough difference occurred to result in a
significant species x position interaction in the 2-way ANOVA test.
When l-way ANOVA's were run independently for GHWF and for VLM,
positional effects were significant for both species. Paired t-tests
comparing % capture for the 2 species were run independently for each
of the 3 board positionings. Significant differences in catch was
seen for the inner vertical (5% level) and the outer horizontal (1%
level) positionings, but not for the inner horizontal positioning.

Study 9. Horizontal Boards Placed, at 3 Heights. Results for Study 9

are seen in Fig. 5. The 2 species responded in almost the exact
opposite manner to this array. The ratio of GHWF capture was 9:33:58
for the 76-cm, 5l-cm, and 25-cm boards, respectively, while the ratio
of VLM capture was 59:32:9. Linear regression of board height against
% capture yielded a regression equation of y = 16.7x + .5 with a
regression coefficient of 2.9 for GHWF, and y = - 17.0x + 67.7 witha
regression coefficient of 2.0 for VLM. These regression coefficients
are significantly different at the 1% level using the t-test,
indicating a significant difference in response of the 2 species to
this array.

Study 10. Boards Piaced at a 45° Angle to the Release Point at 3
Heights. Results for Study 10 are given in Fig. 6. The ratio of GHWF

capture was 45:21:34 for the 76-cm, 5l-cm, and 25-cm boards,
respectively, while the ratio of VIM capture was 55:29:17. Linear
regression of board height against % capture yielded a regression
equation of y = - 3.5x + 41.9 with a regression coefficient of 3.5 for
GHWF and a regression equation of y = 17.6x + 59.8 with a regression
coefficient of 2.5 for VLM. These regression coefficients were not
significant at the 5% level using the t-test, indicating that response
of the 2 species to this array was similar.

Study 11. Effect of Board Angle, at 3 Heights. Results for Study 11
are given in Fig. 7. At the 76-cm height, the ratio of GHWF capture

was 42:35:23 for the 90°, 60°, and 45° boards, respectively,

while the ratio of VIM capture was 26:35:38. Linear regression of
board angle against % capture yielded a regression equation of y =
6.8x + 21.1 with a regression coefficient of 2.1 for GHWF and a
regression equation of y = - 3.7x + 42.4 with a regression coefficient
of 1.1 for VLM. These regression coefficients were significantly
different at the 1% level using the t-test, indicating a significant
difference in response of the 2 species to board angle at the /6-cm
height.

At the 5l-cm height, the ratio of GHWF capture was 35:33:32 for
the 90°, 60°, and 45° boards, respectively, while the ratio of
VLM capture was 21:33:46. Linear regression of board angle against %
capture yielded a regression equation of y = -.1x + 35.3 with a
regression coefficient of 1.9 for GHWF and a regression equation of
y = — 8.2x + 51.3 with a regression coefficient of 1.4 for VLM.
Again,these regression coefficients were significantly different at
the 1% level using the t-test, indicating a significant difference in
response of the 2 species to board angle at the 5l-cm height.

At the 25-cm height, the ratio of GHWF capture was 35:33:32 for
the 90°, 60°, and 45° boards, respectively, while the ratio of
VLM capture was 17:33:49. Linear regression of board angle against %
capture yielded a regression equation of y = 1.0x + 33.2 with a
regression coefficient of 1.3 for GHWF, and a regression equation of
y = ~ 10.2x + 55.2 with a regression coefficient of 1.0 for VLM. Once
again, these regression coefficients were significantly different at
the 14 level using the t-test, indicating a significant difference in
response of the 2 species to board angle at the 25-cm level.

Discussion

Working in fields of tomato and celery in California, Zehnder and
Trumble (1984) reported that a greater proportion of male L. trifolii
and L. sativae were caught on sticky yellow traps in their studies
than females, while pupae reared from foliage indicated that such
catches should have been equal. They suggested that the skewed sex
ratios might be explained in behavioral terms; that is, the females
might spend more time on the leaves during oviposition or the males
might visit a greater number of leaves in search of food and females.
These findings might suggest that sticky yellow cards would be of
little use in the direct control of leafminers if females tended to
avoid such traps. Conditions in both Study 1 and Study 2 of the
present paper were far different from those of Zehnder and Trumble, so
direct comparisons are not warranted. However, Study 1 did indicate
that skewed sex ratios would not be expected in Studies 3-11 of this
paper, especially because there was no plant foliage in these studies
to distract either the males or the females. Study 2, conducted with
chrysanthemums under greenhouse conditions in Baltimore, MD, was not
accompanied by the rearing of individuals from the host foliage to
determine the expected sex ratios. Thus we cannot determine whether
the greater percentage of females than males caught in this study
reflected a behavioral bias or merely reflected an actual skewed sex
ratio in this population. However, we can conclude that Ge etrirolit
females were attracted to and caught on yellow sticky cards in large
numbers, and under certain circumstances may be useful in leafminer
population suppression. Indeed, Herbert et al. (1984) concluded from
tests in commercial greenhouses that growers might be expected to
reduce foliar damage to chrysanthemum crops caused by L. trifolii by
half by hanging sticky yellow boards at 1.5-m spacings. The question
of skewed sex ratios in leafminer populations is an interesting one,
and deserves further study.

Studies 3-11 compared and contrasted adult GHWF responses with
those of VLM adults to arrays of sticky yellow boards. Generally,
GHWF responses were very different, often exactly the opposite, to
those of the VLM. As seen in Study 3, GHWF was influenced by board
size by a factor greater than unity. That is, more GHWF landed per
unit area on the larger boards than the smaller ones. Just the
opposite was seen with VLM, with similar numbers of leafminers landing
on all boards, apparently ignoring board size. Although Study 4
confirmed that GHWF was influenced by board size to a degree greater
than unity, it also demonstrated that distance from the release point
was a far more important factor than mere board size for GHWF. On the
other hand, VLM was as little affected by distance from release point
as it was by board size--it seemingly ignored both. In Study 5, GHWF
greatly preferred the vertical boards to the horizontal ones. This
agrees with results from Studies 3 and 4, since, when viewing the
boards from the release point, the horizontal board would be
perceived as a thin edge, while the vertical board would appear far
larger. On the other hand, VLM apparently preferred the 'thin edge.'
Herbert et al. (1984) compared horizontal boards to vertical boards
for trapping L. trifolii, with mixed results. However, because their
boards were positioned with bottoms 15-cm above the canopy, the boards
would appear somewhat different to flies at canopy level than our
array would appear at our release point. Therefore, results of the 2
studies are not strictly comparable.

Results for Study 6 for GHWF capture was virtually identical to
results for Study 4, with GHWF choosing the larger, closer silhouette
(inner vertical board), while VLM showed a slight preference for the
inner horizontal over the outer vertical board, but no preference for
the inner vertical over the outer vertical board.

Results for Study 7 again demonstrated that GHWF preferred a
closer object that would have been perceived as smaller at the release
point over a more distant, larger silhouette. The VIM also preferred
the inner horizontal board to the outer vertical one, although to a
much less degree than seen for GHWF. This was the first array that
yielded similar capture trends for the 2 species. However, since
2-way ANOVA still gave a significant insect x position interaction, it
is apparent that the 2 species did not respond to the array in exactly
the same way.

Results for Study 8 showed that GHWF preferred the inner vertical
board at 76-cm over the inner horizontal board at 15-cm by a ratio of
79:18. This is less pronounced than the 95:5 ratio seen for vertical
vs horizontal boards placed at the same height in Study 5. This was
because, seen from the point-of-release, the lower horizontal board
would not appear as a thin edge, but would appear larger than the same
board placed at 76-cm. This also probably explains why VLM preferred
the higher vertical board to the horizontal boards placed at 15-cm,
unlike results seen in Study 5. Apparently both GHWF and VLM prefer
to fly outward rather than downward from the point-of-release.

Results in Study 9 were fully consistent, for both pest species,
with the previous results seen in Studies 3-8. As seen from the
point-of-release, the topmost horizontal board would appear to be a
thin edge, while the middle and bottom boards would appear
progressively larger. Thus more whiteflies flew to the apparently
larger silhouette (bottom board) than to the apparently smaller middle
board or to the ‘thin edge' (top board). Conversely, VLM went
preferentially to the 'thin edge' (top board) and progressively less
to the 2 lower boards.

When the horizontal boards of Study 9 were rotated by 45° (Study
10), their perception at the point-of-release was radically altered.
The bottom board would still seem somewhat larger than the other 2
boards, and thus it attracted its share of GHWF. However, the upper
board would now be much more apparent, and being the closest board to
the release point, was the most favored. The VLM once again seemed to
prefer to fly outward to the top board than downward to the 2 lower
boards.

In Study 11, the vertical boards at the 76-cm level would be more
prominent to an observer at the point-of-release than the boards
placed at 60°, which in turn would be more prominent than the boards
placed at 45°. This explained the GHWF preference for 90° over
60° over 45°, As the boards were placed at increasingly lower
levels, all boards would tend to be equally prominent, and thus GHWF
went to all boards equally when they were placed at 5l-cm or 25-cm.
On the other hand, VLM preferred the 45° boards over the 6(0°
boards, and the 60° boards over the vertical boards, when the boards
were placed at 76-cm. This preference successively increased as the
boards were lowered, first to the 5l-cm height, and then to the 25-cm
height. The reason for this preference was not clear, and might form
the basis for future studies.

All of the above has obvious practical significance. When
attempting to catch GHWF, both board area and proximity to the
infestation should be maximized. Other parameters important for using
sticky yellow boards effectively against GHWF are discussed elsewhere
(Webb et al. 1985). For maximum effectiveness, the boards should be
combined with the use of the parasitoid Encarsia formosa Gahan (Webb
and Smith 1980). When attempting to catch VLM, board area and
proximity to the infestation are less important. Thus, the best
strategy for capturing VLM is either to distribute small sticky yellow
cards at many points throughout a greenhouse, or to string thin yellow
sticky tapes just above the crop canopy down the middle of the
greenhouse bed or bench. Placing the card or tape at an angle may
help, but this needs more clarification. In all cases, the small
cards or tapes should be placed just above the crop canopy. —

Acknowledgements

Authors thank Dr. Paul Schwartz, Jr., Beltsville, MD, for advice
on the statistical treatment of the data, Teri Bennett for running the
statistical analyses, and Rhonda Borisko for help with the art work.
Mention of a commercial product in this paper does not constitute
endorsement by the authors or the United States Department of
Agriculture.

Table 1. Release and subsequent recapture after 24-h of adult males
and females of 2 leafminer species. Results of 2 trials
for each species.

Males Females
No. No. No. No.
Trial Released Recaptured Released Recaptured
Liriomyza sativae
1 D2 52 45 43
2 20 19 24 20
be tritotit
1 21 19 25 15
i) 24 i 24 A?

Table 2. Sex ratio of Liriomyza trifolii adults trapped on yellow
sticky cards in a commercial chrysanthemum greenhouse by
dates. Average percentage of 3 boards counted per date.

Total adults ys
Date counted Female
3/8-3/13/84 816 55.0) 2408
3/13-3/20 631 69t 16.5%
3/20-3/27 1473 49+ 8.6
3/27-4/3 2931 60+ 28.6
4/3-4/10 2726 67% 20.7
5/1-5/8 1611 S306 0
6/5-6/12 617 67+ 10.8%
7/3-7/10 611 70* 6.5%
8/7-8/14 3455 61t 4.9%
10/2-10/9/84 376 628) 151.0

* The confidence intervals indicate that significantly more females
than males caught on these dates.

B
Pe CH P
= D
| |
D A 2
eS ilk F
See A Hat Nasa B NW
rears G
g
J 2 Gi saa
= A A
| |
D
S 4 J E
Gor Beak

Figure 1. Diagram of experimental rings, with the position of
boards on the rings designated by the appropriate
letters.

30.6 x 30.6 B04 °x%72.0 4 WOee x. LO. 2

2
Board Size: Gagein

Expected: CH l2 oo 2.12% 6.8% 4.8%
Observed:
Whitefly: 8 1a7o 14.5% 2.9% 1.4%
Leafminer: 33.1% ie ot % 28.9% 15.4%

Figure 2. Effect of board size on % capture of greenhouse whitefly and vegetable
leafminer adults.

Inner Board Outer Board
Pare 277 cm4747742> <A" 777.77 Cm’+7 >—>

Case #1
20.4 x2 04 20.4 x 20.4

% Whitefly: 94

% Leafminer: 51

Cc #
ears ge 30.6 x 30.6 BO 2 084

% Whitefly:

% Leafminer:

Case ¥3
2 10.2 x 10.2 20.4 x 20.4
% Whitefly: 69 37
% Leafminer: 54 46

Figure 3. Effect of board size, and distance from the point-

of-release, on % capture of greenhouse whitefly and
vegetable leafminer adults.

Release Point

Dmarscee7 v CM4+7777 2;

(eaeaaeaeeaa> ——

NJ
(o>)
QO
=.

[«-------

Wrro5
LM:41

Release Point

FIL LAIST

bs |
ro)
2)
3

|n«-------

Figure 4.

Effects of vertical versus horizontal placement on
% capture of greenhouse whitefly (WF) and vegetable
leafminer adults (LM).

Results of horizontal boards (56-cm) vs. vertical
boards (76-cm) placed alternately on the inner ring.
As in 4A, plus an additional vertical (76-cm) board
on the*outer ring.

Release Point

Qeeareen7 i omerer we |emr ree s7 7 cms7s772>>

ba |
o
eo)
3

| SPAM POP PMOL E SS YE y

WE:13

LM:42

56\cm

‘

\
a

Release Point

Peveeee77 CM477-2>..

FLL L SELES

~“N
oO)
(eo)
3

Jaae-eeeee

Figure 4C.

gtrrrra[ 7 Cm 4744772 |

WF:79
LM:65

¢
.
15\cm

Vv
amen

As for 4B, except the vertical (76-cm) board on the
inner ring was removed.

Results of vertical (76-cm) vs. a horizontal board
(15-cm), both on the inner ring, vs. a horizontal
board (15-cm) on the outer ring.

% Whitefly

Release Point % Leafminer

ie; Zoeon ce
9 J, 59

; ,

yy 7

G 7

4 51cm

4 oo 7 32

4 7

4 4

yl ql
764cm y

; ;

4 25 cm

4 58 4 9

4 y,

4 4

y y

‘4

— NANNANAAAAAAAAAAANAAS 5 4 EMA AM |

Figure 5. Effect of horizontal boards placed at 3 heights (25cm,5lcm,76cm) on %
capture of greenhouse whitefly and vegetable leafminer adults.

Release Point

AANAAAAN BS <Ds

NS
(o>)
NWRNAANANR

2)
=

| -—@ \NNNANAANAAAAYR

% Whitefly
45

mal

% Leafminer

<a WS ENAANAAAAARAAAAAAAAAAY 154 cm HENERENRRRRAAAAAAAAAAAAAAA |

Figure 6. Effect of boards placed at a 45°
(25cm,51em, 76cm), on % capture of
miner adults.

angle to the release point

Release Point

ts 7ggg77-) 54 cmrs4s 77777 >>

% Whitefly: 42) 959.23
%Leafminer: PA ey Mie 283!

N
fon)
(7 IS PPP POPPE MPEP

re)
=|

N
rep)

(SOMME PAM L S YD y
oO

Release Point

\
\
\
76\cm
Near ggg 154 CV 47777777742 >
\ \
\ \
\ \
\ 51scm
. . % Whitefly: B5 oct 32
Y . % Leafminer: DAs Ot HAG
iv.

Figure 7. Effect of board angle, at 3 heights, on % capture of
greenhouse whitefly and vegetable leafminer adults.
A. Boards placed at 76-cm.
Dap hcoards placedvat Sl-cm.

Release Point

76cm

mniet eel 54 CM 444477777 yp

. .

25cm

een
% Whitefly: 3 Syeaa 32
% Leafminer: LT 33549

Figure 7C. Boards placed at Zo CMe

References Cited

Affeldt, H.aA., Rows Thimijan, F. F. Smith, and R. E. Webb. 1983.
Response of the greenhouse whitefly (Homoptera: Aleyrodidae) and
the vegetable leafminer (Diptera: Agromyzidae) to photospectra.
J. Econ. Entomol. 76(6):1405-1409.

Herbert hem) oe Rens Smith, and K. B. McRae. 1984. Evaluation of
non-insecticidal methods to reduce damage to chrysanthemums by the
leafminer Liriomyza trifolii (Diptera: Agromyzidae).

Can. Ent. 116(9):1259-1266.

Webb, R. E. and F. F. Smith. 1980. Greenhouse whitefly control of an
integrated regimen based on adult trapping and nymphal
parasitism. Bulletin S.R.0.P./W.P.R.S. III/3:235-246,

Webb, R. E., F. F. Smith, H. A. Affeldt, R. W. Thimijan, R. F. Dudley,
and H. F. Webb. 1985. Trapping greenhouse whitefly with colored
surfaces: variables affecting efficacy. Crop Protection.

Accepted for publication 12/31/84.

Zehnder, G. W. and J. T. Trumble. 1984. Spatial and diel activity of

Liriomyza species (Diptera: Agromyzidae) in fresh market
tomatoes. Environ. Entomol. 13(5):1411-1416.

Liriomyza leaf miners: Potential for Management - A Summary
Sidney L. Poe!

Space in the Entomological Society of America Program for an Informal
Conference on Liriomyza in 1984 is welcome, though not unusual. During
the past few years many state, branch, national and even international
conferences have found time and space for scientists to discuss leaf
MinerSsemelm L951, 1982" 1983 and 1984 special meetings have been called
by leaders of industry and the land grant colleges to address the concerns
raised by the tiny leaf mining flies. Nor is it unusual to have a pro-
ceedings of the conference produced. These have been compiled and issued
for 1981 (Proceedings of the IFAS-Industry Conference on Biology and
Control of Liriomyza leafminers); 1982 (Proceedings of the 3rd Annual
Industry Conference on the Leaf miner, San Diego, CA); and 1984 (Pro-
ceedings of the 4th Annual Conference on the leaf miner, Sarasota, FL).

In addition International conferences in Britain and in Hamburg, Germany
have carried symposia and special sessions on the biology and management
of Liriomyza.

The current meeting represents a continued effort to promote the
excellent communication established among scientists and industry on
this problem. The threat of leaf miners has welded industry leaders,
researchers, and producers together with speed_and in a manner that is
nothinigusnert oc: remarkable. “Other crop industries threatened by other
Species or pests have used the leaf miner as a model for University-
Industry cooperation. That is a major achievement in itself.

Relative to the miner question, what possible new information can
be garnered from this meeting, especially when its participants have
contributed repeatedly to other conferences, even during ‘the. current
year? For one thing, audiences vary from place to place, but at the
ESA meeting entomologists address other entomologists. Consequently,
it provides a forum for critical feedback from colleagues about the
intrinsic worth and potential value of research data obtained in dif-
ferent situations. For another thing, such a forum can be used to
update and report the progress of research and compare notes on the
cyclical population phenomena around the country.

Physiological Plant Response

The emphasis on damage, particularly physiological plant response
to leaf miners, is welcome research since it clearly demonstrates what
growers have attested for years: a high degree of plant part variability
irrespective of insect attack. It is interesting to note that even a
single leaf miner significantly reduced celery viability, and that a
dozen punctures per leaf were sufficient to indicate a significance in
variation. The common assumption that impairment of plant response, 1.¢.
reduced stomatal and mesophyll conductance, transpiration and photosyn-
thesis, at any level is economically detrimental needs ClarificaLvon.

“eae Polytechnic Institute and State University, Department of
Entomology, 216 Price Hall, Blacksburg, VA 24061,

The contrast in control and parasitism between methomyl and methamidophos
is useful in cases where biological mortality is substantial and should
be “sustained,

Biological Control Tactics
ee ee LES:

Species of parasites respond differently to chemical pesticides,
much as does the leaf miner, Organophosphates generally depress parasite
emergence. This was found to be true for Diglyphus, but OP's seemed to
favor Chrysonotomyia. Just the Opposite was true for the pyrethroid
Ambush®, However, relative toxicity of pesticides to both parasite and
host, with concomitant and changing levels of host aVallabiiity 1S. 4
tangle for future students to unravel,

Basic study of parasite biology continues to yield information
that can be translated into a management strategy. High temperatures
of ( > 23.3°C) retarded D. intermedius Oviposition on tomatoes, increased
mortality and resulted in fewer larvae killed per parasite. Host feeding
by this parasite yielded a substantial mortality apart from oviposition.

That species of Liriomyza as well as their parasites vary with the
season has been reaffirmed. Results from a four year Survey reveal that
in Florida the predominant pest leaf miner species shifted from L. sativae
in 1980 tov. trifolii in 19840 Thee data confirm what was surmised to
have occurred in the agricultural semi-tropics when new Practices or
chemical products are introduced,

A practical IPM program for leaf miner and other pests of glass
houses appears to be much closer for Ohio vegetables than for California
chrysanthemums, Parasites released onto populations of leaf miners in
Ohio tomatoes suppressed miner populations to a level where impact on
yield weight was not Sioniticant. Biological control by parasite re-
leases in California was considered a failure due to excessive tempera-
tures)

The success of biological/chemical integrated programs is now a
matter of releasing the best adapted species of parasite into a host
level at a time when the population can be curbed before damage results,

Chemical Control Tactics

An exciting botanical extract of the neem seed has been the sub-
ject of intense study by the USDA. Margosan-O, used as a pot drench,
demonstrates a varied efficacy with host plant species. Generally, the
toxicant reduced larval and pupal development and the emergence of adults.
Life cycle disruption was noted when drenches were applied to beds of
floral plants.

Interspecific Competition

Research into the interactions of two widely different pest species
that attack a common host at the same time provides basic insight into
pest management. The presence of one species tended to suppress the

Be Pe Ses ates of spisc sites «> |
pressed levels of leaf miners. Favorable mite control (with acaricides) 022404876
increased the need to control leaf miners. Miticides had little effect

on parasite activity. The implications of these population phenomena

may in some way be related to the physiological response or celery sto

physical damage noted in an earlier paper.

Visual Response to Sticky Cards

Studies over several years on the response of Liriomyza to visual
stimuli (yellow card) suggest that sex differences do not exist even
though larger numbers of females may be trapped on yellow cards in
chrysanthemums. Likewise, size of the trap and distance from release
point was not significant for the flies, although yellow traps placed
at a 45° angle was preferred over 60° angle and vertical. ‘Practical
use of these responses is given in the advice to distribute a large
number of small yellow cards at many sites throughout the greenhouse.

Conclusions

From the discussions at this conference it is evident that entomolo-
gists know much about Liriomyza spp. that was not known a few years ago.
We can sample the adults, larvae and pupae and do so routinely, in many
different ways. We can count punctures, mines, measure plant height,
weight and physiological responses to the leaf miner. We have developed,
screened, and evaluated a range of chemical toxicants and can predict
mortality under different use patterns. We have recruited natural enemy
parasites trom dirterent’ areas’ of the world’ to help us in our battle to
Control the pest.. We have subjected them (the parasites) to ‘the unnatural
environmental conditions of greenhouse, saranhouse and laboratory chamber
and to the added stress of high or low pest density and an assortment of
chemical fixes.

We have, in short, generated reams of research data about the pest.
But, what have we done to manage the pest? Improved sanitation, i.e. a
clean plant to begin with, has a season-long advantage. A few products
(e.g. Trigard) reduces numbers substantially while nurture of parasites
provides additional mortality. Timing applications for larval control
has®its advantages, sInespite of allthis, many growers still experience
unaccountably large and damaging populations. Why?

The thesis of differing ssusceptibility to insecticides could'be
tested by alternation of product or by judicious use of tank mixes on
a large scale. Host plant resistance, biological control and plant growth
regulators, all proven in experiments to be useful for control have yet
to be integrated into a truly long term managed program. I believe that
soon soil, plant, cultural, environment, chemicals and biological variables
will be included in a strategy to bring leaf miner control in as an integral
part of crop management. Combining entomological knowledge with that of
other crop disciplines and specialists: plant pathologists, weed scientists,
horticulturists, and others will undoubtedly provide the broad framework in
which our theories are real-world tested. We can then assess our progress
on a par with the producer.

June 1985

NATIONAL AGRICULTURAL LIBRARY

wii

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