Relative Effect of Dosage, Droplet Size, Deposit Density, and Droplet Concentration on Mortality of Heliothis virescens (Lepidoptera: Noctuidae) Larvae Treated with Vegetable-oil and Water Sprays Containing Permethrin

Abstract

The relative effects of deposit characteristics (dosage, droplet size, deposit density, and droplet concentration) of permethrin sprays applied in vegetable oil and water on mortality of tobacco budworm, Heliothis virescens (F.), larvae were observed. Mortality of H. virescens larvae in permethrin/vegetable-oil treatments increased with increasing dosage, decreasing deposit density, and decreasing droplet size. Droplet concentration did not significantly influence mortality. Mortality of H. virescens larvae in permethrin/water treatments increased with increasing dosage, increasing deposit density, and decreasing droplet concentration. Droplet size did not significantly influence larva mortality in the permethrin/water data set. In regression models of the data obtained, dosage appeared to be the most important factor influencing mortality of H. virescens larvae with permethrin applied in both vegetable oil and water. However, results from the application of vegetable oil showed that droplet size was as important as dosage; droplet size, however, was not found to be important in the water applications. A comparison of normal applications of permethrin in vegetable oil and water, using the regression models, indicated no differences in resulting mortality of first instars.