Study on β -exotoxin (thurigiensin) effect on biology and growth parameters of Tetranychus urticae Koch (Acari: Tetranychidae) on common bean

Abstract

Abstract :The direct toxicity of β-exotoxin (thurigiensin) of Bacillus thuringiensis Berliner on different stages (reproduction and population development) of Tetranychus urticae Koch were evaluated in laboratory conditions. Immature stages of T. urticae were more susceptible to thuringiensin than adults. Fecundity of T. urticae was significantly reduced when females were exposed to residues for 3 days. At the LC50, larvae and protonymphs were significantly more susceptible to thuringiensin than deutonymphs and adults. Thuringiensin not effect on egg stage. The LC50 on larvae, protonymphs, deutonymphs and adults was 148, 176.6, 293.4 and 318.5 ppm respectively. The daily eggs laid exhibited significant differences among six concentrations of β-exotoxin (thuringiensin) and non-significant difference in the percentage of eggs hatching for all concentrations. The maximum reduction of fecundity for T. urticae was 75% (in 500 ppm).Key words: β –exotoxin, Bacillus thuringiensis, Tetranychus urticae, common bean.