Factors in the Success and Failure of Microbial Insecticides in Vegetable Crops

A search for patterns in the success and failure of microbial insecticides in vegetable crops was conducted through review of four case studies: the use of Bacillus thuringiensis (B.t.) var. tenebrionis for control of the Colorado potato beetle, the use of B.t. var. kurstaki for control of the diamondback moth, the use of various B.t.s for control of lepidopterous pests in tomatoes and celery, and the use of a granulosis virus for control of potato tuber moth. With success defined in terms of achievement of technical goals (efficacy), commercial goals (end-user and insecticide manufacturer satisfaction) and social, or public goals (environmental and health safety), only certain of the case studies could be judged a success. These successes shared a variety of features including: (1) use of the microbial insecticide as a component, rather than as the sole agent, in an integrated crop management program; (2) unavailability of conventional insecticides, due to insecticide resistance, lack of registered products or mandatory IPM programs, provided incentive for the use of microbial insecticides; (3) modification of the expectation that microbial insecticides will perform within the chemical paradigm – fast, lethal and on contact; (4) exploitation of all possible benefits of the microbial insecticide, including safety to natural enemies, as well as efficacy against the target insect, and (5) support from large private and public institutions in the form of research, grower education, scouting programs, subsidized production, and economic and legal incentives to the use of microbial insecticides.