ABSTRACT
Biopesticides, particularly those based on Bacillus thuringiensis (Bt) Berliner, are valuable alternatives to synthetic pesticides. Because of limited stability under fi eld conditions and narrow activity spectrum, their use in pest management represents only a small fraction of the total pesticide usage in agriculture. Deployment of Bt Cry proteins in transgenic plants has overcome some of these drawbacks, and several cultivars of cotton, maize, potato, tomato, and tobacco have been released for cultivation. Use of Bt transgenic crops is expected to reduce pesticide use and provide a capability to control some of the insect pests that have developed high levels of resistance to conventional pesticides. However, concerns have been raised that deployment of insect-resistant transgenic plants will lead to development of resistance in insect populations to the transgene, and to herbicide and antibiotic genes used as selective markers. While some of these concerns may be real, others seem to be highly exaggerated. Therefore, careful thought should be given to the production and release of transgenic crops in different agroecosystems. Insect pest populations have a remarkable capacity to develop resistance, and over 500 species of insects have shown resistance to synthetic insecticides (Georghiou, 1990; Moberg, 1990; Rajmohan, 1998). Therefore, there is a need to take a critical view of resistance to Bt and other novel genes that are being deployed for pest management.
