Insecticide application and coverage: Drop nozzles and higher gallonage applications improve aphid control on lettuce

Good control of the green peach aphid, Myzus persicae (Sulzer), has been obtained during the past few seasons on north coastal counties lettuce and crucifer crops when proper spray or dust coverage was obtained with the recommended insecticides. These trials were conducted in areas of northern California where resistance to the recommended insecticides was claimed. Almost all failures to achieve adequate control could be traced to improper coverage, insufficient gallonage, or incorrect insecticide dosage. Nozzle arrangement and variations in pressure were studied in relation to gallonage output, but these were not found to be so important as speed of travel for achieving proper coverage and eventual control of the aphids attacking lettuce. Some of these trials were compared to commercial applications made by custom operators.