Evaluation of Seed Treatments and in Furrow Sprays for Control of Tobacco Thrips in Cotton, 2016

Selected insecticide treatments were evaluated for control of tobacco thrips in cotton at Lee Farm in Hayward, MO, which is the field location for the Fisher Delta Research Center. Cotton was planted in 9 Jun. The variety planted was PHY339WRF, which is a Roundup Ready variety that includes the two-gene insect protection trait that expresses two proteins from Bacillus thuringiensis (Bt) in cotton plants: Cry1F protein and the Cry1Ac protein. All of the seed also had a standardized fungicide treatment. The test was arranged in an RCB design with four replicates. Individual plots were 13 × 40 ft and planted at a rate of 41,414 seeds per acre. Treatments were either seed treatments of insecticides or insecticides applied in furrow (IF) while planting (Table 1). In-furrow applications were made by TeeJet 0004 StreamJet nozzle operated at 3 mph and 15 psi and applied a solid stream of solution into the furrow approximately 2 inches behind the seed tube at 5 gallons per acre. Granular in-furrow applications were applied with a band applicator operated at 3 mph. An untreated control with untreated cotton seed was also planted. Plots were sampled either by visual inspection for thrips damage and by beating the plant onto a white, Styrofoam serving platter. On each date, 10 samples were taken from the center two rows of all four-row plots. A sample consisted of inspecting all of the plants in five row feet per each of the inner rows. Tobacco thrips, adults and immatures, were counted in each sample and total number of thrips was recorded. Insect control was evaluated 20 Jun—11 days after planting (DAP) at first leaf, 28 Jun at second leaf (19DAP), and 6 Jul at third leaf (27DAP). Data were subjected to ANOVA and means were separated using a protected LSD.

All insecticide treatments resulted in significantly lower numbers of total thrips compared with the untreated check at first leaf evaluation (Table 1). At second leaf, the only treatments that resulted in significantly less thrips than the untreated check were Aeris, Sivanto, and AgLogic IF. At third leaf, only Sivanto IF and Aeris had significantly fewer thrips than the untreated check. Sivanto IF and Aeris seed treatment reduced the number of thrips threefold at first leaf, approximately fourfold at second leaf, and 10-fold at third leaf (27 DAP). Overall, Sivanto IF and Aeris ST offered the best control of thrips when cotton was most vulnerable to damage. No phytotoxicity was observed with any treatment. This research was partially supported by industry gifts of pesticide and seed.

Author notes