The amenability of electrostatic-charged sprays to a wide array of pesticides with different chemistries should be a useful tool in combating insect resistance. Results reported here suggest that the potential exists for obtaining increased efficacy against whiteflies using an electrostatic spray charging system, and that additional research will be required to improve charge-to-mass (Q/M) ratio in order to increase deposition of pest control materials to the lower surfaces of cotton leaves where the whiteflies reside.

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Sweet potato whiteflies (SWF), Bemisia argentifolii, live on the bottom surface of cotton leaves. Except crawlers, nymphal stages of the insect will not move about to contact insecticides. Aerial sprays to suppress SWF require improved application techniques designed to increase spray deposition and penetration to the lower layers of cotton canopy. Using Rotary atomizers, Winglets, and Trumpet nozzles with combination of air speed and boom heights, fenpropathrin 2.4E + acephate 90S at 0.22 + 0.56 kg active ingredient/ha, respectively, were applied at 46.7 L/ha on furrow-irrigated cotton near Maricopa, Arizona. Deposition of active ingredients and season long efficacy against SWF were determined and compared with conventional CP-03 nozzle. Neither spray deposit nor percentage coverage of active ingredients significantly varied consistently between aerial delivery systems. Rotary nozzles produced significantly smaller droplet size and higher droplet density compared to Winglets, Trumpet, and CP-03 nozzles. There was no consistent trend favoring one aerial delivery system over the other treatments against suppression of B. argentifolii on cotton. Further improvements in aerial delivery systems are needed to achieve increased control of insects that live and feed on the bottom surface of cotton leaves.

The % by weight content of leaf-like, stem, boll, seed, and weed materials sifted (3360 mum greater than particle size greater than or equal to 595 mum) from visible wastes of the Shirley Analyzer was determined for a lint sample taken after ginning but before cleaning and for a second lint sample taken after one stage of saw-type cleaning. The % by weight content for bract and leaf increased with decreasing trash particle size. The content of cotton seed coat fragments decreased with reduction in trash particle size. Approximately 1/4 of the botanical wastes consisted of weed materials, including grass particles. Lint cleaning was ineffective in reducing the % by weight content of leaf-like trash. Some selective removal of stem trash occurred as a function of lint cleaning.

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