Evaluation of foliar-applied insecticides for control of plant bugs in cotton, 2024

The efficacy of selected foliar-applied insecticides on tarnished and clouded plant bugs infesting cotton was evaluated at the West Tennessee AgResearch and Education Center in Jackson, TN, in 2024. Cotton seed (‘DP 2038 B3XF’) was planted on 16 May in a no-till field. This test was arranged in an RCB design with 4 replicates. Individual plots were 12.7 × 35 ft and planted at a rate of 4 seeds per row ft on 38-inch row spacing. Treatments were applied with a MudMaster 4WD Multi-Purpose Sprayer equipped with a compressed air high-clearance mounted multi-boom calibrated to deliver 9.4 gpa with 8001 flat fan nozzles. The foliar application was made on 30 Jul to flowering cotton with a plant bug infestation exceeding the UT Extension recommended treatment threshold of 6 plant bugs per 10 row ft. Plant bug nymph and adult population densities were determined by taking 2 drop cloth samples with a standard 2.5 × 2.5 ft black cloth shake sheet in the middle 2 rows of each plot. Plant bug control was evaluated on 1 Aug (2 DAT), 8 Aug (9 DAT), 15 Aug (16 DAT), and 22 Aug (23 DAT). Yield was assessed on 17 Oct by harvesting the 2 center rows of each plot with a spindle picker modified to collect data for small plot research trials and converted using a 40% gin turnout. Data were analyzed using ANOVA statistical procedures, and appropriate transformations were applied when necessary to satisfy model assumptions. Means were separated using Fisher’s Protected Least Significant Difference (P ≤ 0.05). At 2 DAT, Vydate, both rates of Orthene, Brigade + Orthene, and Bidrin significantly reduced immature tarnished plant bug densities compared to the untreated check (Table 1). There were no significant differences among treatments for total plant bug densities at 2 DAT. At 9 DAT, all the insecticide treatments, except Centric, Alias + Orthene, and Couraze Max, significantly reduced immature tarnished plant bug densities. Plots treated with Transform, Brigade + Orthene, and Plinazolin had significantly fewer total plant bugs compared to all treatments except both rates of Orthene, Bidrin, and Diamond at 9 DAT. At 16 DAT, all the insecticide treatments, except Centric, Bidrin, and Couraze Max, significantly reduced immature tarnished plant bug densities compared to the untreated check. Plots treated with Plinazolin had significantly reduced total plant bug densities, compared to all treatments except Brigade + Orthene and Diamond at 16 DAT. At 23 DAT, plots treated with Orthene at 1.1 lb/acre and Plinazolin had significantly reduced immature tarnished plant bug densities compared to all treatments except Orthene at 0.77 lb/acre, Brigade + Orthene, and Diamond. Plots treated with Plinazolin had significantly reduced total plant bug densities compared to all insecticide treatments except Orthene at 1.1 lb/acre, Brigade + Orthene, and Diamond at 23 DAT. There were no differences in yield among treatments. No phytotoxicity was observed with any treatment. Means within columns followed by a common letter are not significantly different (Fisher’s Protected LSD, P > 0.05). Immature tarnished plant bugs. Tarnished + clouded plant bugs, adults + immatures. oz wt/acre. fl oz/acre. lb/acre. lb ai/acre. v/v in %. This research was supported in part by Cotton Incorporated and industry gifts of pesticide and seed. None declared.