A RAPID METHOD FOR SCREENING INSECTICIDES IN THE LABORATORY

An efficient method for rapidly mass-screening insecticides for use ag ainst sap-feeding virus vectors is presented with a case study of 30 c hemicals. The method permits large numbers of insecticides to be teste d simultaneously and relatively inexpensively in a sequence of laborat ory bioassays. The sequence is designed to find the most effective pes ticide at the lowest concentration giving control without phytotoxicit y. The system was derived to test candidate insecticides to control to mato yellow leaf curl virus vectored by the tobacco whitefly, Bemisia tabaci Gennad., the most serious pest of greenhouse and field tomatoes in the Middle East. Although the insecticides were all more efficacio us in the laboratory than in the field, bioassay results were highly c orrelated with results from field trials, giving high confidence that the screening process selected only the most efficacious insecticides. Most of the insecticides accepted by the screening process have since been adopted by vegetable growers in Israel. The method is not intend ed to eliminate field efficacy trials, but to reduce the number of tri als and treatments that need to be performed, thereby reducing costs. The method provides for the optimization of application rates which wi ll contribute to the expected life of insecticides before resistance d evelops, and will also help to reduce environmental contamination. In addition, the method is suitable for estimating relative efficacy for pesticide benefits assessments, a required part of the (re-)registrati on process for pesticides in some countries. Although developed for sc reening insecticides against virus-transmitting sap-feeding insects, t he method could be modified to assess the efficacy of insecticides in controlling other insect pests.