The present invention relates to the field of recombinant DNA technology. In particular, it relates to methods for using genes encoding pesticidal proteins to control pests on agronomic important plants.
Synthetic chemicals are relied on extensively for protection against a wide variety of pests in the agriculture and forestry industries. The use of chemical pesticides, however, have posed several problems. In particular, many insect pests have developed resistance to widely used compounds. In addition, widespread use has led to concerns about environmental pollution. Many of these compounds have deleterious effects on non-target organisms, such as birds, and humans. The compounds may also accumulate in the food chain and affect natural predators of insect pests.
These concerns have led to increased emphasis on alternative pest management strategies. For instance, genes from viruses and bacteria that encode proteins that are toxic to insects and other pests have been used to control pests. The most commonly used of these proteins is a toxin protein from a gram-positive soil bacterium, Bacillus thuringiensis (Bt toxin). B. thuringiensis produces a proteinaceous paraspore or crystal which is toxic upon ingestion by a susceptible insect host. The cloning and expression of Bt toxin genes has been described in the literature (Schnepf, H. E. and Whitely, H. R. Proc. Natl. Acad. Sci. USA 78: 2893-2897 (1981)). U.S. Pat. Nos. 5,236,843, 5,26,166, and 5,135,867. Transgenic plants expressing this protein have been used to control a variety of plant pests.
The use of transgenic plants in food crops raise other problems, however. For instance, public resistance and added regulatory burdens hinder the production and sale of transgenic food crop plants. In addition, in the case of perennial crops, the cost of replacing orchards, vineyards and the like with transgenic cultivars may be prohibitive.
Thus, a need exists for new approaches to apply the advances in plant genetic engineering to control pests. The present invention addresses these and other needs.