Time Response to Direct Vs. Indirect Exposure to Aphicides, 1990

Abstract

Abstract A colony of the cotton aphid was established from aphids collected at Stoneville, MS, and was bioassayed after 3 mo in culture. Individual greenhouse-grown cotton leaves (DES-119, nontreated seed) were sprayed with formulated insecticides at recommended field rates using a laboratory spray chamber calibrated to deliver 6 gal/acre at 30 psi with a TX6 cone nozzle moving at 2 mph. Each leaf was sprayed either on the top surface or on the underside of the leaf and allowed to' dry. Controls consisted of leaves sprayed with water only. Aphids were then caged in ventillated clip cages on the underside only of leaves, so that aphids recieved either indirect or direct exposure to insecticides, depending on which side of the leaf was sprayed. Cumulative mortality was determined for 24 and 48 h of exposure, during which time treated leaves and aphids were held in a laboratory chamber at 80°F, 14:10 L:D and 50% RH. For each insecticide tested, 6 leaves (replications) were treated and 10 adult female aphids were caged on each leaf. Statistical comparisons were made for percent mortality within a chemical treatment for time and method of exposure. All tests were not conducted on the same day, so statistical comparisons were not made among chemicals.