Efficacy of selected foliar insecticides against thrips in cotton, 2024

Efficacy of Acephate, Dimethoate, Intrepid Edge, Plinazolin, Radiant, and Transform broadcast against thrips in cotton was evaluated at Suffolk, VA in 2024. “Deltapine 2333 B3XF” seed (with the stored seed protection rate of imidacloprid) were planted on 16 May in a strip-tilled field. No at-plant insecticides were applied. Plots were 4 rows wide (36-in row centers) by 35-ft long, in a 4-replicate RCB design. Treatments were broadcast at the early first true leaf stage on 31 May with a CO₂-pressurized backpack sprayer calibrated to deliver 14.8 gpa through XR110015-VS nozzles (2 nozzles per row). The adjuvant “Dyne-Amic” was tank-mix applied with all products. Thrips injury and populations were assessed at 4-5DAT (second true leaf stage) and 11DAT (4-5 true leaf stage). Thrips injury was estimated visually on a 0 to 5 scale, where 0 = no injury and 5 = dead plants. Thrips counts were taken by collecting 5 plants per plot in Mason jars containing soapy water; thrips were separated from the solution using vacuum filtration onto gridded filter paper, then immatures and adults were counted under magnification. Plant vigor was evaluated visually at 11 days after treatment (DAT) on a scale of 1-9, where 9 equaled the best vigor. Data were analyzed using analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) statistical procedures.

For thrips injury, there were no differences among treatments at 5DAT (Table 1). At 11DAT, all products except Transform had lower thrips injury than the untreated check. All insecticides except Transform reduced the number of immature thrips on both sample dates relative to the untreated check. Adult thrips counts differed at 4DAT, but not at 11DAT. Intrepid Edge, Plinazolin, and both rates of Acephate had a lower number of adult thrips relative to the untreated control. Plant vigor ratings ranged from 3.3 to 4.8, with the low rate of Radiant and Intrepid Edge having higher plant vigor relative to the untreated control. Adult thrips species composition averaged across treatments and sample dates was 49% tobacco thrips, 44% western flower thrips, and 7% other or not identified.¹

Footnotes