Differential mortality response of lepidopteran defoliators to insecticides deposited within three strata of wide- and narrow-row soybeans

Field studies were conducted at two locations within Mississippi to determine the efficacy of aerially applied insecticides within the canopies of wide- and narrow-row soybeans. Permethrin (central Mississippi) or methyl parathion (south Mississippi) was applied to both canopies via fixed-wing aircraft and plots were sampled on four postapplication dates. Data suggest that the degree of larva mortality from insecticides differs between row-spacing systems at each vertical stratum. In general, narrow row widths reduced the overall efficacy of an insecticide, but the magnitude of the difference was dependent on the target species. These data are significantly correlated with data on physical penetration of the insecticide, but a great deal of variation is left unexplained.