Integration of a Photoelectrically Operated Intermittent Sprayer with Action Level Thresholds for Control of Lepidopteran Pests of Cabbage

A photoelectrically operated intermittent (POI) sprayer and a continuous sprayer were used both on a weekly basis and in conjunction with the attainment of action level, insect density thresholds to apply methomyl to spring- and summer-planted cabbages for the control of the imported cabbage worm, Pieris rapae (L), and cabbage looper, Trichoplusia ni (Hubner). In the spring planting, since imported cabbage worms appeared late in the season and action levels were only exceeded in two mstances after growing plants had merged in the row, there was no difference in the amount of insecticide applied by either type of sprayer when action levels were used. The POI sprayer used to apply sprays to the spring planting on a weekly basis, however, used 21% less spray material than the continuous unit so used. With summer-planted cabbages, savings in pesticide over the amount used in once-a-week applications with the continuous sprayer were 35, 40, and 52%, respectively, for the contmuous sprayer use in conjunction with action level thresholds, the POI sprayer used on a weekly basis, and the POI sprayer used with action level thresholds. In both spring and summer plantings, quality and quantity of produce from treated plots were similar.