ABSTRACT

Cotton defoliants Dropp, Def, and Prep, carried in water or oil and applied with a direct-injection sprayer, an irrigation system simulator, or an irrigation center pivot, were evaluated in field plats of cotton during 1990 and 1991. Defoliants applied with the direct-injection sprayer generally removed a higher percentage of leaves with more consistency than did defoliants applied with the irrigation system simulator. Defoliants applied with the simulator removed a higher percent of the leaves when they were mixed with a non-emulsifiable oil than when they were mixed with water. The effectiveness of defoliants was not influenced by carriers when they were applied with the direct-injection sprayer. Dropp and Def chemigated in combination were consistently more effective as defoliants of cotton than when either chemical was applied independently. A mixture of Dropp (0.06 lbs AI/A) + Def (0.94 lbs Al/A) chemigated with oil as a carrier removed from 80 to 95% of the cotton leaves, thus indicating that chemigation can be an acceptable method for applying cotton defoliants.