Economics of Managing Lepidopterous Cabbage Pests In the Southwestern United States

Studies were conducted in 1989 and 1990 at Lane, Oklahoma, to evaluate the economic benefits of managing lepidopterous pests of fresh-market cabbage using Bacillus thuringiensis Berliner var. kurstaki, or a pyrethroid insecticide in combination with an economic threshold based on larval density. Marketable cabbage yield and percent head damage were not significantly different among plots sprayed weekly compared with those sprayed according to the economic threshold, regardless of the type of insecticide used. Among weekly and threshold-based spray programs with both types of insecticides, fewer sprays were required with a pyrethroid/threshold program whereas the most applications were needed in the weekly-scheduled regimes. When timing was based on the economic threshold, control with the biological insecticide required more sprays than that with the pyrethroid. The least insecticide cost and greatest net returns were achieved when a pyrethroid/threshold regime was followed. The biologicallthreshold program required more sprays because more time was needed to effect larval mortality and thus larval counts changed less rapidly. Data were obtained from pesticide applicator professionals and cabbage producers to determine the effects of diamondback moth, Plutella xylostella (L.), insecticide resistance on the economics of managing lepidopterous pests of cabbage in the southwestern United States. Total amounts of insecticides used, numbers of applications, and total costs of pest control programs increased substantially in two cabbage production areas of southwestern United States where diamondback moth control failures have been observed.