Abstract
A spore-crystal complex of Bacillus thuringiensis AF101 strain (serotype 4a:4b) was at least 25 times more toxic than that of B. thuringiensis A3Cl strain (serotype 4a:4b) tow and the larvae of the fall webworm, Hyphantria cunea. Toxicities of purified preparation of spores, crystals, and spore-crystal mixtures were tested using fourth-instar larvae of H. cunea to determine the effects of the existence of spores on toxicity. Spores of both strains showed low toxicity. In contrast, crystals of both strains show-ed high toxicity and AF101 crystals were at least 25 times more toxic than those of A3C1. By the addition of the spores of each strain, the toxicity of AF101 crystals increased about 4 times and the larvae were killed more rapidly. These results indicate that the presence of the spores intensifies the toxicity of AF101 crystals toward the larvae of H. cunea.
