Effects of Mixtures of Bacillus thuringiensis and Pesticides on Plutella xylostella and the Parasite Thyraeella collaris124

Abstract

Dipel®, a commercial formulation of Bacillus thuringiensis Berliner, was combined with 7 pesticides, and their effects against 3rd instars of Plutella xylostella (L.) were determined by using a leaf-dip method. Binapacryl, tricyclohexyltin hydroxide, chlordimeform, and fentin hydroxide synergised B. thuringiensis by factors of 5.5, 4.2, 4.2, and 3.7, respectively, at the LC₅₀ level; demeton-S-methyl and dimethoate were highly antagonistic. When the synergistic mixtures were tested against Thyraeella collaris Gravely, a parasite of P. xylostella, those containing binapacryl, tricyclohexyltin hydroxide, and fentin hydroxide were not toxic; the chlordimeform mixture displayed some vapor and stomach activity but no contact toxicity.