Pesticide delivery systems can effect deposition on canopies and resultant biological effects of the toxicant at any given point throughout the canopy. The present study assessed the effects of two insecticides (Cypermethrin and Spinosad) provided by different nozzles on biological efficacy and feeding behavior, applied to two different canopies (Corn, Soybean) at 10 and 20 GPA, using different nozzles and the capstan pulsing system. Biological efficacy was estimated using second larvae instar of fall armyworm on corn and soybean. Six replicates were used for each combination of insecticide, application rates, nozzles, canopies, and plant sections. The biological efficacy, feeding behavior, and consumption rates were determined.
Results showed that the total deposit from each nozzle and resulting mortality was higher on the top followed by middle, and bottom sections for both canopies. The larvae showed avoidance behavior on Cypermethrin treated leaf disks. The implications of the development of resistance in each presentation scenario are reported elsewhere. The effects of nozzles flow rates, canopy, sections, insecticides, and hours post treatment on mortality and consumption rates showed that all main factors had a significant effect on mortality. The effect of hours post treatment accounted for the greatest portion of the variability. Mortality and consumption rates were significantly different on different canopies and hours post treatments. LSD tests indicated that the effects of nozzles, and flow rates were significantly different on mortality but had no significant effect on consumption rate. The results suggest that using different application equipment on various canopy architectures can present significant differences in deposit patterns and resulting biological efficacy.
Species 1: Lepidoptera Noctuidae Spodoptera frugiperda (fall armyworm)
Keywords: biological efficacy, insecticide deposit pattern
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