The major insect pests on cotton in California are the pink bollworm and the tobacco budworm in the southern desert valleys, and lygus bugs in the San Joaquin Valley. Presently many growers, especially in the desert areas, apply insecticides on a scheduled program. This practice not only increases production costs but also eliminates beneficial insects and leads to pesticide resistance in the target species. In an effort to rationalize the application of such insecticides, a slide rule was developed that incorporates the phenol ogies of the cotton plant and the major pests to time the application of insecticides at optimal periods of efficacy. This paper updates the progress on the slide rule and illustrates its usage.

The data base used for the slide rule consists of several years of field-collected data relative to the development of both the cotton plant and insects. These data have been converted to a time scale of heat units or degree days (DD) and statistically modeled for predictive purposes as discussed in the preceding paper. The slide rule itself is constructed of plastic with several colors and is accompanied by a manual describing its operation.