The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
9 HiUME LIBRAi,,
AGRICULTURAL RESEARCH & EDUCATION CENTER LIPRAI
tm IFAS, University of Florida
Bradenton, Florida OCT 1979
UTILIZATION OF INSECTICIDES FOR INSECT PEST MANAGE ,FRA.S.- Univ. of Florid.
ON TOMATOES IN FLORIDA ---
D. J. Schuster, D. E. Dougherty, P. H. Everett
Bradenton AREC Research Report GC1979-9 May 1979
Tomatoes in Florida are attacked by many insect pests including the tomato
pinworm, Keiferia lycopersicella (Walsingham), the southern armyworm, Spodoptera
eridania (Cramer), the cabbage looper, Trichoplusia ni (Hubner), and the vegetable
leafminer, Liriomyza sativae Blanchard. Damage to the plants is inflicted during
the larval or immature stages of the insects' life cycles. All but the leafminer
are "worms" which feed on the foliage and the fruit and are considered primary pests.
The leafminer attacks only the foliage and is considered a secondary pest. That is,
under "normal" conditions in nature, environmental (unfavorable temperature, rain-
fall, etc.) or biotic (parasites, predators and diseases) factors keep population
densities below economically damaging levels. When the balance between the leaf-
miner and ,ts parasites is upset by the heavy use of chemicals such as methomyl
(Lannate\ NudrintRJ) to control primary pests, outbreaks of the leafminer have
been shown to occur (Oatman and Kennedy 1976). In addition to the danger of
inducing outbreaks of secondary pests, the heavy use of insecticides.commonly leads
to the development of resistance in the pest insects to the chemicals applied for
their control. This is the situation which apparently existed in the Spring of
1977 when treated tomato plants suffered up to 90% defoliation by L. sativae
(Schuster 1978). Later investigations indicated no significant control of this
insect with chemicals available in 1977 (Schuster 1979). Although newer, more
effective insecticides have since been registered, the development of resistance
to these chemicals may occur in the future. Secondary pest outbreaks and resistance
of pests to chemicals have prompted the everincreasing demand for pest management.
"Pest management may be defined as the reduction of the pest problems by
actions-selected after the life systems of the pest are understood and the
ecologic as well as economic consequences of these actions have been predicted,
as accurately as possible, to be in the best interest of mankind" (Eabb 1970).
Although insect pest management (IPM) on tomatoes has not yet reached the refined
state implied by the above definition, sufficient advances in knowledge, particu-
larly with regards to insecticide use, have been made to implement IPM on the
grower level. Of the so-called "primary" insect pests mentioned earlier, the
tomato pinworm is probably the most important because of the difficulty to control
it. Heavy use of insecticides aimed at this pest causes, at least in part, the
periodic outbreaks of leafminers experienced by tomato growers in south Florida.
As a result, much of the work reported here is directed at controlling the tomato
pinworm, as well as other lepidopterous pests, with a minimum of disturbance of
the vegetable leafminer and its parasites. Work will also be described which
focuses on the control of the leafminer, when this becomes necessary, with as
little upset as possible of the leafminer parasite complex.
IPM, as it is now being most widely practiced in Florida tomato production,
involves the periodic application of insecticides for the control of lepidopterous
larvae and other insect pests. The insecticides selected for this type of
preventive program are those which have the least detrimental impact on the
parasites of the vegetable leafminer. Poe et al. (1978) demonstrated that
significantly more leafmine(R arasites emgrged from foliage from tomato plots
treated weekly with Phosvel' + Thiodan than from untreated foliage (check)
or foliage treated with any of the other insecticides or insecticide combinations
tested (Table 1). Although the number of leafminers was reduced by all insecticide---_
treatments, the average number of leafminers exceeded the economic threshold of
25 miners/6 trifoliates (42/10 trifoliates) established by Pohronezny and
Waddill (1978) in all cases except for Lannate plus a reduced rate of Vydate.
FoliagR from plots sprayed with Bolstar R), Monitor(R) and a higher rate of
,Vydate yielded fewer parasites than untreated foliage. Oatman and Kennedy
(1976) demonstrated that the 0.45 lb. rate of Lannate, when applied alone, induced
increases in the number of leafminers, in part, by reducing the percent parasitism
of this pest (Table 2). This effect on the number of leafminers was not apparent
until after 8 applications, although the effect on parasitism a noted afhtr as
few as 3Rapplications. Bacillus thuringiensis Berliner (Dipel Bactur' ,
Biotrol ') is apparently non-toxic to leafminer parasites. In order to determine
if this material might play a role in IPM, Dipel was applied weekly to tomatoes
alone or in combinations with Lannate or Thiodan. Even though no insecticide
treatment reduced pinworm damaged to foliage, all treatments reduced foliar
damage of other lepidopterous larvae (primarily southern armyworm and cabbage
-looper) (Table 3). All treatments increased the number of undamaged fruit while-
/ only Thiodan (1.0 lb) plus Dipel reduced the number damaged by the pinworm.
Reductions in fruit damaged by lepidopterous larvae were noted for all treatments
relative to the check. Reduced rates of Lannate in combination with Dipel at
rates as low as 0.25 lb. were as effective as the higher Lannate rate (0.45 lb.).
Although the impact of this rate of Lannate on leafminer parasites is not known,
it should be less detrimental than the higher rates presently used. Adding Dipel
to the Thiodan increased the control of the tomato pinworm on fruit.
Selection of insecticide or insecticide combinations that are less toxic
to parasites than are alternatives for inclusion into a regular, preventive
spray schedule is one step in IPM. Ideally, however, insecticides would not be
administered until pest populations approached levels that would economically
damage the tomato crops. In this type of program, regular scouting by trained
personnel would keep the grower or his adviser informed of the insect situation
in the field. Insecticides, especially those with minimal impact on natural
enemies (parasites) of the pests, would be applied 'as needed'. In order for
this approach to work, however, insecticides must be identified which efficiently
control the target pest with one application. Toward this end, several studies
have been completed on fruiting tomato plants which were being heavily damaged
by either the tomato pinworm or the southern armyworm. Acceptable control
(> 80%) of the pinwr m with registered insecticides was obtained with only
Lannate or Guthions (Table 4). Best control was noted with the synthetic
pyrethroids AmbushM and Pounce(R, neither of which is cleared for this pest
on tomatoes. In an experiment where the majority of southern armyworm larvae
were large (Fall 1977), Lannate alone gave the most rapid control (Table 5).
However, Lannate at 0.25 lb plus Dipel, Thiodan at 1.0 lb plus Dipel, Monitor and
Guthion gave good control 7 days after spraying. When a greater proportion of
small larvae were present (Fall 1978) these same treatments plus Thiodan alone
controlled the pest up to 7 days after application. Knockdown was also quicker
with these treatments in the 1978 experiment.
If the population densities of leafminers increase to damaging levels despite
efforts to conserve parasites by selecting less toxic insecticides or applying
insecticides as needed for control of the pests, there are currently two
insecticides, Vydate and Monitor, which are registered in Florida and which
are still effective (Schuster 1979). Weekly applications of these insecticides
at normal use rates have significantly reduced the number of leafminer parasites
while reducing the number of mines on foliage by a maximum of 64% (Table 1).
When Vydate was applied at different intervals on two tomato cultivars, one
application every two weeks on 'Walter' and one every week on 'Floradel' were
required to reduce the number of leafmineson foliage (Table 6). However, even
at frequencies of application as high as two per week, the degree of control was
only 58.8% on Walter and 59.8% on Floradel. The number of leafminer adults
emerging from foliage of either cultivar was not significantly reduced while
applications as frequent as one per week reduced the number of emerging parasite
adults on both cultivars. When Vydate and Monitor were applied only once,
significant reductions in the number of emerging leafminers were observed after
only one day posttreatment (Table 7). No significant effect on the number of
emerging parasites was detected for any spray. As a result, the percent
parasitism was significantly increased one and three days posttreatment for
Monitor and the highrate of Vydate. Not only, then, were immediate reductions
in the leafminer population apparent, but the increased parasitism noted could
further reduce the population in the future.
Thiodan alone, or in combination with Dipel, and Lannate at reduced rates
in combination with Dipel were shown as effective as higher rates of Lannate when
applied in preventive (scheduled) spray programs or as 'clean-up' sprays for
southern armyworm larvae. The application of insecticides as-needed is preferred
since development of resistance by the target insects would be slower. Both
Thiodan and Lannate are cholinesterase inhibitors and might rapidly result in
insect resistance if used in a regular, protective schedule. More work needs
to be completed to determine if the above insecticidal combinations are effective
in controlling the tomato pinworm'in a treat as-needed' program. Vydate and
Monitor applied regularly may be counter productive since marginal leafminer
control and high parasite mortality (89.7 95.1%) was observed in experimental
Trade names have been used for the convenience of the reader. Use of trade
names is with the understanding that no discrimination is intended and no
endorsement by the University of Florida or the authors is implied, to the
exclusion of other, equally effective materials.
Oatman, E. R., and G. G.
sativae on tomato.
Kennedy. 1976. Methomyl induced outbreak of Liriomyza
J. Econ. Entomol. 69:667-668.
Poe, S. L., P. H. Everett, D. J. Schuster, and C. A. Musgrave. 1978. Insecticidal
effects on Liriomyza sativae larvae and their parasites on tomato. J. Ga.
Entomol. Soc. 13:322-327.
Pohronezny, K. L., and V. Waddill. 1978. Integrated pest management development
of an alternative approach to control of tomato pests in Florida. Univ. Fla.
Ext. Plant Pathol. Rept. No. 22. 7 pp
Rabb, R. L. 1970. Introduction to the conference. Pages 1-5 in R. L. Rabb and
F. E. Guthrie, eds. Concepts of pest management. North Carolina State Univ.
Schuster, D. J. 1978. Vegetable leafminer control on tomato, 1977. Insecticide
Acaricide Tests 3:108.
Schuster, D. J. 1979. Vegetable leafminer control on tomato, 1977-78. Insecticide
Acaricide Tests 4: (in press).
Schuster, D. J., C. A. Musgrave, and J. P. Jones. 1979. Vegetable leafminer and
parasite emergence from tomato foliage sprayed with oxamyl. J. Econ. Entomol.
72: (in press).
Table 1. Effect of weekly insecticide applications on the vegetable
and its parasites on tomato (from Poe et al. 1978).
Lb. ai/ Leafmines/10 No. adults emerged/20 trifoliates
Material 100 gal. trifoliates Leafminers Parasites % parasites
Lannate 1.8L + 0.45 39.2 a1 32.0 N.S. 8.8 ab 21.5 a-c
Vydate 2L 0.38
Vydate 2L 0.75 42.9 ab 30.3 5.5 a 15.4 a
Polstar 6EC 1.00 47.2 ab 33.3 7.0 a 17.4 ab
Monitor 4EC 0.50 47.7 ab 26.0 5.3 a 16.8 ab
Phosvel 45WP + 0.75 48.6 ab 50.0 9.3 ab 18.4 ab
Vydate 2L 1.00
Monitor 4EC + 0.25 52.2 bc 22.0 12.5 ab 36.2 b-d
Orthene 75SP 0.25
Orthene 75SP. 0.50 61.7 c 36.0 14.3 ab 28.4 a-c
Lorsban 4EC 1.00 62.2 c 30.0 10.0 ab 24.8 a-c
Phosvel 45WP + 0.75 87.9 d 34.5 43.8 c 55.9 d
Thiodan 50WP 0.50
Check 108.6 e 29.8 21.0 b 41.4 cd
significantly different -':
1f:eens v:ithin columns followed by the same letter are not
the P = C.05 level, least significant difference.
Table 2. Effect of Methomyl (Lannate, Nudrin) applications on the number of leafmines
and percent parasitism of the vegetable leafminer on tomato (from Oatman and
Cumulative No. mines/man-hour search % parasitism
Sample number of Methomyl Methomyl Untreated Methomyl Methomyl Untreated
date applications (0.90 lb) (0.45 lb) (0.90 lb) (0.45 lb)
6/26 1 18.7 a1 15.7 a 24.0 a 80 94 96
7/23 4 364.7 a 417.3 a 354.7 a 48 58 80
8/20 8 4097.3 a 4513.3 a 2922.6 b 12 8 69
9/3 9 9585.0 a 11390.7 a 5220.0 b 5 12 55
1Means in horizontal rows followed by the same letter are not significantly different
at P = 0.05, Duncan's multiple range test.
Table 3. Control of lepidopterous larvae on tomatoes sprayed weekly with insecticides.
Lepidopterous larval Number of fruit
Lb. ai/ foliar damage 1 Pinworm Other
Material 100 gal. Pinworm Other Undamaged damaged damaged
Thiodan 2EC 0.45 32.0 ab2 6.8 a 129.5 a 21.2 ab 4.2 a
Lannate 1.8L 1,00 12.5 a 3.3 a 127.5 a 26.2 ab 6.5 a
Dipel WP 1.50 57.8 bc 0.5 a 105.7 a 16.0 ab 4.0 a
Dipel WP 1.00 37.0 a-c 1.8 a 129.2 a 26.2 ab 2.7 a
Dipel WP 0.50 55.3 bc 1.5 a 119.0 a 26.5 ab 12.0 a
Lannate 1.8L + 0.225 27.0 ab 0.5 a 129.0 a 26.5 ab 0.5 a
Dipel WP 0.50
Lcnnate 1.8L + 0.225 30.0 ab 1.5 a 125.8 a 19.7 ab 1.0 a
Dipel WP 0.25
Thiodan 2EC + 1.00 43.5 a-c 0.8 a 135.7 a 13.5 a 2.7 a
Dipel WP 0.50
Th-cdan 2EC + 0.50 70.8 c 1.8 a 143.0 a 25.7 ab 5.2 a
Dipel WP 0.50
Check 39.0 a-c 15.0 b 59.0 b 32.0 b 34.7 b
1Other lepidopterous larvae
present were primarily the southern armyworm and the
Means within columns followed by the same letter are not significantly different at
the P = 0.05 level, Duncan's multiple range test.
Table 4. Percent control (relative
larvae on tomato on 1 and
to the untreated check) of tomato pinworm
3 days following a single insecticide
Material lb. ai/100 gal 1 day 3 days
Pounce 3.2EC 0.1 99.5 a1 94.1 a
Ambush 2EC 0.1 91.9 ab 94.9 a
Duter 19WP 1.5 88.1 a-c 70.5 b-d
Lannate 1.8L 1.0 85.4 b-d 76.8 bc
Orthene 75SP 1.0 84.6 b-d 72.1 b-d
Guthion 50IP 1.0 80.8 b-d 85.4 ab
Pydrin 2.4EC 0.1 77.8 b-e 61.9 c-e
Vydate 2L 1.0 75.0 b-e 75.9 bc
Thiodan 2EC 1.0 74.3 b-e 70.0 b-d
Vendex 50WP 1.5 70.3 b-e 57.0 de
Azodrin 5EC 1.0 69.8 b-e 76.8 bc
Dylox 80SP 1.0 67.3 c-e 31.3 f
Diazinon 50UP 1.0 65.0 c-e 57.5 e
Bolstar 6EC 1.0 63.5 c-e 62.4 c-e
Monitor 4EC 1.0 66.0 de 73.0 b-d
Dibrom 8EC 1.0 62.9 de 51.3 e
Trithion 4EC 1.0 61.2 de 63.5 c-e
Plictran 50WP 0.5 50.2 e 62.0 c-e
Cygon 2.67EC 0.5 46.8 f 64.9 c-e
Marlate 50UP 1.5 24.9 g 33.8 f
Check 0.0 h 0.0 g
1Means within columns followed
ferent at the P = 0.05 level,
Table 5. Percent control
on tomato 1, 3,
by the same letter are not significantly dif-
Duncan's multiple range test.
(relative to the untreated check) of southern armyworm larvae
and 7 days following a single insecticide application.
Lb. ai/ Fall 1977 Fall 1978
Material 100 gal 1 day 3 days 7 days 1 day 3 days 7 days
Monitor 4EC 1.00 57.6a-c1 62.2a-e 92.0ab 97.6a 99.2a 97.8a
Guthion 50UP 1.50 44.4bc 56.7a-e 87.4ab 58.5b-d 90.2ab 97.8a
Marlate 50UP 3.00 41.8a-c 53.0b-e 71.0a-c 30.2de 73.2ab 63.7b
Diazinon 501P 0.25 31.8cd 40.8b-e 33.6de -
Dipel UP 1.50 43.6a-c 48.1b-e 67.4a-d 41.4c-e 72.6ab 81.1ab
Dipel UP 1.00 11.4cd 18.8ef 54.1b-d 51.6b-d 79.5ab 80.6ab
Dipel UP 0.50 36.7bc 30.5d-f 80.lab 10.3ef 45.7b 56.1b
Thiodan 2EC 1.00 19.0cd 37.7c-f 41.2cd 86.7a 98.0a 98.5a
Lannate 1.8L 0.90 90.3a 96.8a 98.8a 96.0a 99.2a 94.7a
Lannate 1.8L 0.45 94.9a 89.0ab 97.8a 95.0a 99.6a 98.5a
Lannate 1.8L + 0.25 86.6ab 80.0a-c 95.9a 97.4a 97.7a 94.1a
Dipel UP 1.00
Lannate 1.8L + 0.25 96.6a 98.3a 96.9a
Dipel UP 0.50
Thiodan 2EC + 1.00 48.7a-c 67.4a-d 88.8ab 83.3ab 99.6ab 98.2a
Dipel UP 1.00
Thiodan 2EC + 1.00 81.4a-c 95.3a 93.5a
Dipzl IP 0.50
Thiodan 2EC + 0.50 21.2cd 21.5d-f 35.7cd -
Dipel WP 1.00
Check 0.Od 0.Of 0.Oe O.Of 0.Oc 0.Oc
the P = 0.05
columns followed by the same letter are not significantly different at
level, Duncan's multiple range test.
Table 6. Effect of Vydate applications (0.5 ai/100 gal) on the vegetable leafminer
and its parasites on two tomato cultivars (from Schuster et al. 1979).
anpi' cati on Leafmi nes/10 Number adults emerged/30 trifoliates
frT':,icy. trifoliates Leafminers Parasites % parasites
2 per week 49.1 al 35.8 N.S. 6.4 a 17.5 a
1 per week 80.7 b 56.2 31.4 ab 34.2 ab
1 per 2 weeks 86.9 b 60.4 37.2 bc 37.5 b
1 per 3 weeks 98.6 bc 60.2 51.8 bc 42.7 b
None 119.3 c 62.0 62.4 c 50.8 b
2 per week 32.7 a 43.0 a 3.6 a 8.9 a
1 per week 53.7 b 61.0 a-c 27.2 ab 29.4 bc
1 per 2 weeks 62.0 bc 80.6 bc 28.8 ab 28.6 b
1 per 3 weeks 70.9 bc 58.0 ab 51.6 bc 46.4 d
None 81.3 c 89.6 c 74.0 c 40.0 cd
1Means within columns followed by the same letter are not significantly different at
the P = 0.05 level, Duncan's multiple range test.
Table 7. Effect of a single insecticide application on the vegetable leafminer and
its parasites on tomato (from Schuster et al. 1979).
Lb. ai/ Number adults emerged/50 trifoliates
Material 100 gal. Leafminers Parasites % parasites
1 Day Posttreatment
Monitor 4EC 0.75 25.7 al 156.7 N.S. 91.5 a
Vydate 2L 1.00 56.7 ab 169.7 74.1 ab
Vydate 2L 0.50 52.3 ab 131.3 73.2 b
Vydate 2L 0.25 89.7 b 189.7 68.5 bc
Check 186.3 c 222.3 54.2 c
3 Days Posttreatment
Monitor 4EC 0.75 17.7 a 112.0 N.S. 90.9 a
Vydate 2L 1.00 -51.3 a 116.7 70.2 bc
Vydate 2L 0.50 47.0 a 150.7 77.1 b
Vydate 2L 0.25 56.0 a 140.0 68.4 bc
Check 106.0 b 158.0 60.5 c
7 Days Posttreatment
Monitor 4EC 0.75 9.7 a 116.0 N.S. 87.7 N.S.
Vydate 2L 1.00 7.0 a 119.7 92.1
Vydate 2L 0.50 20.3 ab 208.7 91.2
Vydate 2L 0.25 39.7 b 210.0 81.1
Check 70.7 c 167.3 71.0
within columns followed by the same letter are
= 0.05 level, least significant difference.
not significantly different at