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Group Title: Research Report - University of Florida Agricultural Research and Education Center ; GC1981-4
Title: Insecticides for management of insect pests on tomatoes in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00056126/00001
 Material Information
Title: Insecticides for management of insect pests on tomatoes in Florida
Series Title: Research Report - University of Florida Agricultural Research and Education Center ; GC1981-4
Physical Description: Book
Language: English
Creator: Schuster, David J.
Price, J. F.
Everett, P. H.
Publisher: Agricultural Research & Education Center, IFAS, University of Florida
Publication Date: 1981
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Bibliographic ID: UF00056126
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 62381503

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HISTORIC NOTE


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not reflect current scientific knowledge
or recommendations. These texts
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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
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(EDIS)

site maintained by the Florida
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Copyright 2005, Board of Trustees, University
of Florida





AGRICULTURAL RESEARCH & EDUCATION CENTER
IFAS, University of Florida
Bradenton, Florida
Bradenton AREC Research Report GC1981-4 May 1981

INSECTICIDES FOR MANAGEMENT OF INSECT PESTS ON TOMATOES IN FLORIDA
D. J. Schuster, J. F. Price, and P. H. Everett

INTRODUCTION
Tomatoes in Florida are attacked by many insect pests including the tomato pin-
worm, 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; i.e. in most seasons,
environmental (unfavorable temperature, rainfall, etc.) or natural factors (para-
sites, predators and diseases) keep population densities below economically damaging
levels. When.the balance between the leafminer and its parasites is upset by the
weekly applications of chemicals such as methomyl (Lannate, Nudrin ) to control pri-
mary 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 in-
discriminate use of insecticides frequently leads to the development of resistance in
the pest insects to the chemicals applied for their control. This is the situation
which might have existed in the spring of 1977 when treated tomato plants suffered
up to 90% defoliation by leafminers (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 ever increasing
demand for integrated pest management (IPM).

"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" (Rabb 1970). Although insect pest
management on tomatoes has not yet reached the refined state implied by the above
definition, sufficient advances in knowledge, particularly with regards to insecti-
cide 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. Frequent use of insecticides
aimed at this pest may cause, at least in part, the periodic outbreaks of leafminers
experienced by tomato growers in south Florida. As a result, much of the work re-
ported here is directed at controlling the tomato pinworm, as well as other lepidop-
terous pests, with a minimum of disturbance of the vegetable leafminer and its para-
sites. Work will also be described which focuses on the control of the leafminer,
when this becomes necessary, with minimum disruption of the leafminer parasite
complex.

EXPERIMENTAL FINDINGS
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 with insecticides applied as needed for leafminer
control. The insecticides selected for this type of preventive program are those
which have the least detrimental impact on the parasites of the vegetable leafminer.





-2-


Poe et al. (1978) demonstrated that significantly more leafminer parasites emerged
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 leafmines was
reduced by all insecticide treatments, the average number of leafmines exceeded
the economic threshold of 25 mines/6 trifoliates (42/10 trifoliates) established
by Pohrgnezny and Waddill (1978) in all cases. Foliage from plots sprayed with
Bolstar and Monitor yielded fewer parasites than untreated foliage. Oatman and
Kennedy (1976) demonstrated that the 0.45 lb AI 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 was noted
after as few as 3 applications.
Bacillus thuringiensis Berliner (Dipel Bactur Biotrol ) does not kill
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 damage to foliage,
all treatments reduced foliar damage of other lepidopterous larvae (primarily
southern armyworm and cabbage looper) Table 3). All treatments produced higher
numbers of undamaged fruit while only Thiodan (1.0 lb AI) plus Dipel reduced the
number damaged by the pinworm. Reductions in fruit damaged by lepidopterous larvae
were noted for all insecticides compared 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 AI).

One step in IPM is the selection of insecticide or insecticide combinations
that are less toxic to parasites than are alternatives for inclusion into a regular,
preventive spray schedule. Ideally, however, insecticides would not be applied
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. Insecti-
cides, 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 infested with larvae of the tomato pinworm, the southern
armyworm, the tomato fruitworm, or cabbage looper. Acceptable control ( > 80%) of
the pinworm with registered insecticides was obtained with only Lannate or Guthion
(Table 4). Best control was noted with the synthetic pyrethroids Ambusho and
Pounce 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 AI plus
Dipel, Thiodan at 1.0 lb AI 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. In the final test in a commercial tomato field, Lannate alone, Lannate
at 0.225 lb AI plus Dipel at 0.5 lb, Ambush, Thiodan alone and Thiodan at 1.0 lb AI
plus Dipel at 0.5 lb gave good control of cabbage looper and tomato fruitworm larvae
one day after treatment (Table 6). All treatments except those containing Thiodan
gave good control of southern armyworm larvae after one day. Two days later treat-
ments containing Lannate or Thiodan controlled larvae of all of the above species
of lepidopterous larvae. Control of larvae of the southern armyworm and tomato
fruitworm was not significant 3 days after treatment with Ambush. Sprays with
Thiodan and the reduced rate of Lannate were least detrimental to the percentage
of leafminer parasites emerging from treated foliage.







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 is currently one insecticide,
Monitor, which is registered in Florida and which is still effective (Schuster 1979).
Weekly applications of this insecticide at a normal use rate has significantly re-
duced the number of leafminer parasites while reducing the number of mines on fol-
iage by a maximum of 56% (Table 1). However, when Monitor was applied only once,
a significant reduction in the number of emerging leafminers was observed after
only one day posttreatment (Table 7). No significant effect on the number of
emerging parasites was detected. As a result, the percent parasitism was signi-
ficantly increased one and three days posttreatment. Not only, then, were imme-
diate reductions in the leafminer population apparent, but the increased parasitism
noted could further reduce the population in thelfature.

DISCUSSION

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 cer-
tain lepidopterous 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. Applying Monitor
regularly may be counter productive since leafminer control may be counter balanced
by high parasite mortality (89.7 95.1%).

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.
REFERENCES CITED
Oatman, E. R., and G. G. Kennedy. 1976. Methomyl induced outbreak of Liriomyza
sativae on tomato. 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 CaroliniaState Univ., Raleigh.

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).





-4-


Table 1. Effect of weekly
its parasites on


insecticide applications on the vegetable
tomato (from Poe et al. 1978).


leafminer and


Lb. ai/ Leafmines/10 No. adults emerged/20 trifoliates
100 gal. trifoliates Leafminers Parasites % parasites
Bolstar 6EC 1.00 47.2 a1 33.3 7.0 a 17.4 ab
Monitor 4EC 0.50 47.7 a 26.0 5.3 a 16.8 ab
Monitor 4EC + 0.25 52.2 ab 22.0 12.5 ab 36.2 b-d
Orthene 75SP 0.25
Orthene 75SP 0.50 61.7 b 36.0 14.3 ab 28.4 a-c
Lorsban 4EC 1.00 62.2 b 30.0 10.0 ab 24.8 a-c
Phosvel 45WP + 0.75 87.9 c 34.5 43.8 c 55.9 d
Thiodan 50WP 0.50
Check 108.6 d 29.8 21.0 b 41.4 cd

1Means within columns followed by the same letter are not significantly different at
the P = 0.05 level, least significant difference.


------ -------- w---------------------




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
Kennedy 1976).

Cumulative No. mines/man-hour search % parasitism
Sample number of MethomyI Methomyl Untreated Methomyl Methomyl Untreated
date applications (0.90 lb) (0.45 lb) (0.90 lb) (0.45 1b)

6/26 1 18.7 al 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 11890.7 a 5220.0 b 5 12 55

IMeans in horizontal rows followed by the same letter are not significantly different
at P = 0.05, Duncan's multiple range test.






-5-


Table 3. Control of lepidopterous larvae on tomatoes sprayed weekly with insecticides
(ARC-Immokalee, spring 1978).


Lepidopterous larval Number of fruit
Lb. ai/ foliar damage Pinworm Other
Material 100 ga. Pinworm Other1 Undamaged damaged damaged

Thiodan 2EC 1.00 32.0 ab2 6.8 a 129.5 a 21.2 ab 4.2 a
Lannate 1.8L 0.45 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 55.8 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
Lannate 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
Thiodan 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


10ther lepidopterous larvae
cabbage looper.


present were primarily the southern armyworm and the


2Means 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 to the
larvae on tomato on 1 and 3 days
application (AREC-Bradenton, spri


untreated check) of tomato pinworm
following a single insecticide
ng 1977).


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 50WP 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 50WP 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 50WP 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,


by the same letter are not significantly dif-
Duncan's multiple range test.








Table 5. Percent control (relative to the untreated check) of southern armyworm larvae
on tomato 1, 3, and 7 days following a single insecticide application (AREC-
Bradenton).

Lb. ai/ Fall 1977 Fall 1978
Material 100 gal. 1 day 3 days 7 day 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 50WP 1.50 44.4bc 56.7a-e 87.4ab 58.5b-d 90.2ab 97.8a
Marlate 50WP 3.00 41.8a-c 53.0b-e 71.0a-c 30.2de 73.2ab 63.7b
Diazinon 50WP 0.25 31.3cd 40.8b-e 33.6de -
Dipel WP 1.50 43.6a-c 48.1b-e 67.4a-d 41.4c-e 72.6ab 81.1ab
Dipel WP 1.00 11.4cd 18.8ef 54.1b-d 54.1b-d 79.5ab 80.6ab
Dipel WP 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 96.3a 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.Oa-c 95.9a 97.4a 97.7a 94.1a
Dipel WP 1.00
Lannate 1.8L + 0.25 -- 96.6a 98.3a 96.9a
Dipel WP 0.50
Thiodan 2EC + 1.00 48.7a-c 67.4a-d 88.8ab 83.3ab 99.6ab 98.2a
Dipel WP 1.00
Thiodan 2EC + 1.00 81.4a-c 95.3a 93.5a
Dipel WP 0.50
Thiodan 2EC + 0.50 21.2cd 21.5d-f 35.7cd -
Dipel WP 1.00
Check O.Od O.Of O.Oe O.Of O.Oc O.Oc

1Means within columns followed by the same letter are not significantly different at the
P = 0.05 level, Duncan's multiple range test.








Table 6. Effect of a single insecticide application on lepidopterous larvae and leafminer
(Manatee County, spring 1979).


parasitism


No. larvae/man-hour search % leafminer
1 day post-treatrient 3 days post-treatment parasitism
Treatment and Southern Cabbage Tomato Southern Cabbage Tomato 3 days -
lb ai/acre armyworm looper fruitworm armyworm looper fruitworm post-treatment

Lannate 90SP 0.90 0.0 a1 0.3 a 0.0 a 0.0 a 0.0 a 0.3 a 18.9 d
Lannate 90SP 0.225
+ Dipel WP 0.50 0.7 a 1.6 a 0.0 a 2.0 ab 0.7 a 0.3 a 32.5 bc
Ambush 2EC 0.10 3.1 a 0.9 a 0.0 a 10.3 bc 0.9 a 1.3 ab 20.2 cd
Thiodan 50WP 1.00
+ Dipel WP 0.50 6.4 ab 1.6 a 0.0 a 4.7 ab 0.0 a 0.3 a 38.3 ab
Thiodan 50WP 1.00 11.3 ab 2.3 a 0.3 a 3.6 ab 2.9 a 0.7 a 37.5 ab
Water check 22.0 b 6.7 b 2.0 b 19.6 c 10.9 b 4.7 b 52.2 a


1MHans within a column followed by
Duncan's multiple range test.


the same letter are not significantly different at the 5% level by











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 Post-treatment

Monitor 4EC 0.75 25.7 a1 156.7 N.S. 91.5 a
Check 186.3 b 222.3 54.2 b
3 Days Post-treatment

Monitor 4EC 0.75 17.7 a 112.0 N.S. 90.9 a
Check 106.0 b 158.0 60.5 b

7 Days Post-treatment

Monitor 4EC 0.75 9.7 a 116.0 N.S. 87.7 N.S.
Check 70.7 b 167.3 71.0


1Means within columns followed by the same letter are
at the P = 0.05 level, least significant difference.


not significantly different




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