Second-generation Glyphosate-Resistant Cotton Tolerance to Combinations of Glyphosate with Insecticides and Mepiquat Chloride

Abstract

Field trials were conducted in 2005 and 2006 to evaluate application of glyphosate alone or plus the plant growth regulator mepiquat chloride with 20 different insecticides to second-generation glyphosate-resistant cotton at the pinhead square or first bloom growth stages. At 7 DAT, averaged across cotton growth stages and herbicide treatments, combination with insecticides profenofos and methomyl resulted in 5 and 9% plant injury, respectively, and were the only insecticide combinations that resulted in injury greater than glyphosate or glyphosate plus mepiquat chloride applied alone. By 14 DAT, cotton injury was less than 2% for all treatments. Averaged across cotton growth stages and insecticides, addition of mepiquat chloride to glyphosate resulted in a 4 and 6 cm height reduction at 7 and 28 DAT, respectively. Seed cotton yield and percent first harvest were similar for all treatments, indicating that cotton injury and height reductions observed after application did not result in yield reductions or maturity delays. Glyphosate combined with insecticides and mepiquat chloride, in accordance with herbicide labeling for second-generation glyphosate-resistant cotton, offers producers the ability to integrate pest and crop management strategies and reduce application costs with minimal effect on the crop.Nomenclature: Acephate, acetamiprid, bifenthrin, cyfluthrin, cypermethrin, dicrotophos, dimethoate, emamectin benzoate, gamma-cyhalothrin, glyphosate, imidacloprid, indoxacarb, lambda-cyhalothrin, mepiquat chloride, methomyl, novaluron, oxamyl, profenofos, spinosad, thiamethoxam, thiodicarb, zeta-cypermethrin, cotton, Gossypium hirsutum L