Miticide Efficacy Against Twospotted Spider Mites on Cotton, 2019

Selected miticides were evaluated for control of a twospotted spider mite (TSM) infestation on cotton in a grower field in Gleason, TN that had surpassed the economic threshold of 30–50% of plants showing injury with mites present. Cotton was planted on 8 May 2019 on a 30-inch row spacing. The test was arranged in an RCB design with four replicates. Individual plots were 12.5 × 40 ft. Treatments were applied with a high clearance sprayer calibrated to deliver 9.4 GPA at 40 PSI with 8001 flat fan nozzles. The foliar application was made 3 Jul to flowering cotton with a spider mite infestation well in excess of the recommended treatment threshold. Adult and immature TSM were counted in a 1-inch² area from the underside of 10 leaves of plants from the center two rows (10 inch² total) of all plots. TSM were counted 6 and 9 DAT. Data were subjected to ANOVA, and means were separated using a protected LSD.

All miticide treatments significantly reduced the number of TSM at the initial evaluation timing compared with the untreated check (Table 1). At 6 DAT, plots treated with an unregistered experimental compound had significantly fewer TSM than all other treatments except Oberon. Oberon provided significantly more reduction in TSM than Apollo and the lower rate of Denim. By 9 DAT, the experimental treatment reduced TSM numbers more than any other treatment, and plots treated with Oberon had fewer TSM than did those treated with Apollo or Denim. No phytotoxicity was observed with any treatment.¹

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