Efficacy of foliar-applied insecticides on thrips in Mississippi cotton, 2023

On 9 May 2021, an insecticide trial was planted at the Delta Research and Extension Center in Stoneville, MS, to evaluate the efficacy of foliar-applied insecticides for thrips management. Plot size was 4 rows wide by 40 feet in length on 40-inch centers. Field studies were implemented as a randomized complete block design with 4 replications. All plots received applications with a MUDMASTER, 4WD Multi-Purpose Sprayer (Bowman Manufacturing, Newport, AR) equipped with a compressed air high-clearance mounted multi-boom calibrated to deliver 10 gallons per acre at 50 PSI using TX-6 Hollow Cone nozzles (2 nozzles per row) (TeeJet Technologies, Glendale, IL). Thrips density samples and damage ratings were taken at 3, 5, and 11 DAT. At each sample date, 5 plants were randomly selected from the innermost 2 rows and placed in self-sealing plastic bags to be taken to the lab for processing. Plants were soaked in a bleach, dish soap, and water solution to subdue thrips and then washed onto filter paper. The filter paper was then vacuum suctioned, and thrips were counted under a microscope. Damage ratings were conducted by assessing the average plant damage on a whole plot scale of 0–5, with 0 being no damage and 5 being plant death.

At 3 DAT, Orthene 90S at 0.52 lb. ai/ac had the lowest damage rating and was the only treatment that was not similar to the untreated check. At the same sample date, Intrepid Edge 3F, Orthene 90S at 0.52 lb. ai/ac, and Torac 1.29SC had the lowest adult thrips densities and were the only treatments that separated from the untreated check. There were no differences in immature thrips among any treatments (Tables 1 and 2). At 5 DAT, there was no mean separation among treatments for damage thrips or thrips densities (Tables 1 and 2). At 11 DAT, Plinazolin 400DC had the lowest damage rating, and it was the only treatment to separate from the untreated check. At the same sample date, Orthene 90S at 0.52 lb. ai/ac, Radiant 1SC, Bidrin 8EC, Plinazolin 400DC, and Renestra 0.64DC + Orthene 90S had the lowest number of immature thrips and were only similar to Torac 1.29SC, Dimethoate 4EC, Orthene 90S at 0.21 lb. ai/ac, and Intrepid Edge 3F. No differences were observed among treatments for the adult thrips densities (Tables 1 and 2).¹

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