抄録
Toxicity of the supernatant from liquid culture of Bacillus thuringiensis serovar kurstaki strain KB500 was investigated with and without pellet against larvae of three lepidopteran species, the common cutworm, Sphodoptera litura, the diamondback moth, Plutella xylostella, and the smaller tea tortrix, Adoxophyes sp. using a diet incorporation method. Supernatant shoed a lower larvicidal activity than that of pellet or whole culture against all three insects tested. Interestingly, however, a strong synergistic effect was shown in the supernatant when mixed with pellet. This effect was detected on S. litura larvae only. The toxicity of the mixture of supernatant and pellet against S. litura was enhanced up to 32 times higher than that of pellet alone. The lower larvicidal activity and synergism in the supernatant might be derived from different substances. The former larvicidal activity could be explained by soluble δ-endotoxin in the supernatant but the latter synergism might be due to unknown substance(s).
