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ROUNDUP-INSECTICIDE SYNERGY EVALUATION ON THRIPS, 2005

ROUNDUP-INSECTICIDE SYNERGY EVALUATION ON THRIPS, 2005 (F32) COTTON: Gossypium hirsutum L., ‘DP 543 BGII/RR’ Fred R. Musser Department of Entomology and Plant Pathology Mississippi State University P.O. Box 9775 Mississippi State, MS 39762 Phone: (662) 325-2085 Fax: (662) 325-8837 E-mail: fm61@msstate.edu Angus L. Catchot E-mail: acatchot@entomology.msstate.edu Thrips, primarily tobacco thrips: Frankliniella fusca (Hinds) Many insecticide applications are now being done in conjunction with an application of glyphosate herbicide. Since formulated glyphosate alters the leaf chemistry of the crop, it was suspected that the efficacy of insecticides may be improved when applied with this herbicide. To test this hypothesis, a field test was conducted at the Plant Science farm at Mississippi State, MS. The trial consisted of 4 replications of 6 treatments in a RCB. The treatments were Bidrin + Roundup, Orthene + Roundup, Bidrin, Orthene, Roundup and an untreated check (Table 1). Each plot was 4 rows wide (38- inch rows) and 40 ft long and planted 10 May in conventionally tilled ground. Treatments were applied to the middle two rows of each plot on 25 May for thrips control using a backpack sprayer calibrated to spray 10 gpa. Thrips populations were monitored 2 and 7 DAT by removing 5 randomly selected plants from each plot and placing them in a plastic bag. In the laboratory, each plant was washed and sieved, and thrips were collected on filter paper where they were counted under a microscope. Data analysis was conducted using PROC MIXED in SAS 9.1. Data was transformed by square root to equalize variance. Statistical differences were measured using LSD with P=0.05. To evaluate the impact of Roundup on the efficacy of Bidrin and Orthene together, an ESTIMATE statement was used within PROC MIXED with both sampling dates evaluated together as repeated measures. At 2 DAT, all the treatments containing insecticide reduced adult and immature thrips populations below those treatments without insecticides and there were no differences between insecticide treatments with and without Roundup. At 7 DAT, immature populations in the untreated check and Roundup alone treatments were lower than at 2 DAT. No treatments had adult thrips densities significantly different from the untreated check. However at 7 DAT, all insecticide treatments except Orthene had immature populations significantly lower than the untreated check. When combining the adult and immature populations at 7 DAT, the only treatments significantly lower than the untreated check were the treatments with insecticide plus Roundup. However there were no significant differences among the four insecticide treatments at any time in the trial. An overall estimate of the impact of Roundup on the efficacy of the two insecticides on total thrips populations was marginally significant at P=0.079. Therefore it appears that mixing Roundup with insecticides slightly increases the efficacy of insecticides against thrips. Mean number of thrips per 5 plants 2 DAT 7 DAT lb (AI)/ Treatment/formulation acre Adults Nymphs Total Adults Nymphs Total Bidrin 8EC 0.20 1.0a 1.0a 2.0a 2.0a 3.0a 5.0a + Roundup Weathermax 0.75 Orthene 90S 0.20 0.8a 3.8a 4.5a 1.8a 1.5a 3.2a + Roundup Weathermax 0.75 Bidrin 8EC 0.20 0.8a 2.8a 3.5a 3.5ab 4.8a 8.2ab Orthene 90S 0.20 0.0a 2.5a 2.5a 3.0ab 9.0ab 12.0abc Roundup Weathermax 0.75 5.2b 50.2b 55.5b 7.0b 13.8b 20.8c Untreated check --- 5.5b 44.0b 49.5b 3.8ab 14.2b 18.0bc Means within columns followed by the same letter are not significantly different (Fisher’s Protected LSD; P = 0.05) based on square root transformed data. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Arthropod Management Tests Oxford University Press

ROUNDUP-INSECTICIDE SYNERGY EVALUATION ON THRIPS, 2005

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Oxford University Press
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© Published by Oxford University Press.
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2155-9856
DOI
10.1093/amt/32.1.F32
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Abstract

(F32) COTTON: Gossypium hirsutum L., ‘DP 543 BGII/RR’ Fred R. Musser Department of Entomology and Plant Pathology Mississippi State University P.O. Box 9775 Mississippi State, MS 39762 Phone: (662) 325-2085 Fax: (662) 325-8837 E-mail: fm61@msstate.edu Angus L. Catchot E-mail: acatchot@entomology.msstate.edu Thrips, primarily tobacco thrips: Frankliniella fusca (Hinds) Many insecticide applications are now being done in conjunction with an application of glyphosate herbicide. Since formulated glyphosate alters the leaf chemistry of the crop, it was suspected that the efficacy of insecticides may be improved when applied with this herbicide. To test this hypothesis, a field test was conducted at the Plant Science farm at Mississippi State, MS. The trial consisted of 4 replications of 6 treatments in a RCB. The treatments were Bidrin + Roundup, Orthene + Roundup, Bidrin, Orthene, Roundup and an untreated check (Table 1). Each plot was 4 rows wide (38- inch rows) and 40 ft long and planted 10 May in conventionally tilled ground. Treatments were applied to the middle two rows of each plot on 25 May for thrips control using a backpack sprayer calibrated to spray 10 gpa. Thrips populations were monitored 2 and 7 DAT by removing 5 randomly selected plants from each plot and placing them in a plastic bag. In the laboratory, each plant was washed and sieved, and thrips were collected on filter paper where they were counted under a microscope. Data analysis was conducted using PROC MIXED in SAS 9.1. Data was transformed by square root to equalize variance. Statistical differences were measured using LSD with P=0.05. To evaluate the impact of Roundup on the efficacy of Bidrin and Orthene together, an ESTIMATE statement was used within PROC MIXED with both sampling dates evaluated together as repeated measures. At 2 DAT, all the treatments containing insecticide reduced adult and immature thrips populations below those treatments without insecticides and there were no differences between insecticide treatments with and without Roundup. At 7 DAT, immature populations in the untreated check and Roundup alone treatments were lower than at 2 DAT. No treatments had adult thrips densities significantly different from the untreated check. However at 7 DAT, all insecticide treatments except Orthene had immature populations significantly lower than the untreated check. When combining the adult and immature populations at 7 DAT, the only treatments significantly lower than the untreated check were the treatments with insecticide plus Roundup. However there were no significant differences among the four insecticide treatments at any time in the trial. An overall estimate of the impact of Roundup on the efficacy of the two insecticides on total thrips populations was marginally significant at P=0.079. Therefore it appears that mixing Roundup with insecticides slightly increases the efficacy of insecticides against thrips. Mean number of thrips per 5 plants 2 DAT 7 DAT lb (AI)/ Treatment/formulation acre Adults Nymphs Total Adults Nymphs Total Bidrin 8EC 0.20 1.0a 1.0a 2.0a 2.0a 3.0a 5.0a + Roundup Weathermax 0.75 Orthene 90S 0.20 0.8a 3.8a 4.5a 1.8a 1.5a 3.2a + Roundup Weathermax 0.75 Bidrin 8EC 0.20 0.8a 2.8a 3.5a 3.5ab 4.8a 8.2ab Orthene 90S 0.20 0.0a 2.5a 2.5a 3.0ab 9.0ab 12.0abc Roundup Weathermax 0.75 5.2b 50.2b 55.5b 7.0b 13.8b 20.8c Untreated check --- 5.5b 44.0b 49.5b 3.8ab 14.2b 18.0bc Means within columns followed by the same letter are not significantly different (Fisher’s Protected LSD; P = 0.05) based on square root transformed data.

Journal

Arthropod Management TestsOxford University Press

Published: Jan 1, 2007

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