Tomatoes, an important tropical crop, suffer greatly from various plant viruses which are transmitted by the tobacco (sweetpotato) whitefly, Bemisia tabaci. Since these viruses cannot be controlled directly, the only path available to the grower is to prevent their transmission. The shortcomings of chemical control are well known and the use of alternative control methods is limited. Consequently, resistant cultivars would be the best solution for the grower. Breeding for resistance to the whiteflies as vectors of viruses has some clear advantages compared with breeding plants resistant to the virus. In search for sources of resistance among wild tomatoes, the two most resistant accessions of Lycopersicon pennellii, L. hirsutum and L. hirsutumf. glabratum were selected. Although these accessions are susceptible to the virus, in the field they were only slightly, or not, infested. The resistance of L. pennellii was found to be based entirely on the sticky material which is exuded by glandular trichomes located on the leaves and stems. The rate of resistance depends partially on environmental factors like photoperiod and light intensity. A reliable method for quantitative detection of resistance in L. pennellii was developed.

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An efficient method for rapidly mass‐screening insecticides for use against sap‐feeding virus vectors is presented with a case study of 30 chemicals. The method permits large numbers of insecticides to be tested simultaneously and relatively inexpensively in a sequence of laboratory bioassays. The sequence is designed to find the most effective pesticide at the lowest concentration giving control without phytotoxicity. The system was derived to test candidate insecticides to control tomato 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 efficacious in the laboratory than in the field, bioassay results were highly correlated 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 intended to eliminate field efficacy trials, but to reduce the number of trials and treatments that need to be performed, thereby reducing costs. The method provides for the optimization of application rates which will contribute to the expected life of insecticides before resistance develops, 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‐)registration process for pesticides in some countries. Although developed for screening insecticides against virus‐transmitting sap‐feeding insects, the method could be modified to assess the efficacy of insecticides in controlling other insect pests.

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