Evaluation of Insecticides For Control of Plant Bugs in Flowering Cotton, 2017

Selected insecticides, alone or in tank-mixtures, were evaluated for control of tarnished and clouded plant bugs in flowering cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 16 May 2017. The test was arranged in an RCB design with four replicates. Individual plots were 12.67 × 40 ft and planted at a rate of four seeds per row ft on 38-inch row spacing. Treatments were applied with a high clearance sprayer calibrated to deliver 9.2 gpa at 40 psi with 8001 flat fan nozzles. The first application was made 24 Jul (Appl 1) to flowering cotton when plant bugs exceeded the economic threshold of six plant bugs per ten row feet. A second application was made (7 Aug, Appl 2) as populations in most treated plots again exceeded this threshold. Plots were sampled with a standard 2.5- × 2.5-ft black cloth shake sheet by placing the sheet between two rows and vigorously shaking plants to dislodge insects. On each date, two shake sheet samples were taken on the center two rows (10-row ft total) of all plots. Plant bug control was evaluated 28 Jul, 4 d after initial application (4 DAT1), 1 Aug (8 DAT1), 4 Aug (11 DAT1), and 11 Aug (4 DAT2). Yield was taken 9 Oct by harvesting the two center rows with a spindle picker modified to collect data for small plots. Data were analyzed by analysis of variance (ANOVA) and means were separated by an F-protected Least Significant Difference (LSD, P < 0.05). Nontransformed means are presented in the table.

All insecticide treatments significantly reduced plant bugs numbers found at all evaluation timings compared with the untreated check (Table 1). At 4 DAT1, plots treated with Dimethoate had more immature tarnished plant bugs than those that received any of the other insecticide treatments. Also, Orthene alone reduced total plant bug numbers more than Dimethoate and the Orthene plus Diamond tank-mixture. By 8 DAT1, plots treated with Orthene alone had fewer immature tarnished and total plant bugs than those treated with Dimethoate or Bidrin. Plots treated with Dimethoate had more total plant bugs than those that received any of the other insecticide treatments, except Bidrin at 11 DAT1. At 4 DAT2, plots treated with the tank-mixture of Orthene plus Diamond had fewer total plant bugs than those treated with Bidrin or Transform alone. All insecticide treatments increased seed cotton yield compared with the untreated check. Plots treated with Orthene alone yielded more than plots treated with Bidrin alone. No phytotoxicity was observed with any treatment.

This research was partially supported by industry gifts of pesticide and seed.