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ENY275: Microbial Insecticides

Figure 1. Action of Bacllus thuringiensis var. kurstaki on caterpillars. (1) Caterpillar consumes foliage treated with Bt (spores and crystalline toxin). (2) Within minutes, the toxin binds to specific receptors in the gut wall, and the caterpillar STOPS FEEDING. (3) Within hours, the gut wall breaks down, allowing spores and normal gut bacteria to enter the body cavity; the toxin dissolves. (4) In 1-2 days, the caterpillar dies from septicemia as spores and gut bacteria proliferate in its blood. (Adapted from Abbot Laboratories, "Mosquito Control: Taking the Bite Out of Summer.")