Abstract
The synergistic effects of supernatants from cultures of nine strains of Bacillus thuringiensis toward the insecticidal activity of δ-endotoxin were investigated using neonates of the common cutworm, Spodoptera litura, and late 3rd instar larvae of the diamondback moth, Plutella xylostella by the diet incorporation method. Synergistic effects between supernatants and δ-endotoxins were detected against S. litura but not toward P. xylostella. Synergistic activity in supernatants against S. litura but not toward P. xylostella. Synergistic activity in supernatants against S. litura was observed in four strains and the occurrence was shown to be dependent on culture media. Interestingly, B. thuringiensis serovar japonensis strain Buibui and B. thuringinensis serovar morrisoni strain san diego, which produce insecticidal crystal proteins specific only to coleopteran larvae, were shown to produce synergistic factor(s) in culture supernatants. The synergistic substance(s) released into supernatants from various strains of B. thuringiensis were apparently the same.
