Insecticidal Activity of Crystals and Spores of Purified Bacillus thuringiensis 00-50-5 Strain against Trichoplusia ni Hubner

摘要

[Objective] The paper was to study pathogenic mechanism and action mode of Bacillus thuringiensis( Bt) 00-50-5 strain against Trichoplusia ni Hubner.[Method] The crystals and spores of B.thuringiensis 00-50-5 strain were first isolated and purified,and their insecticidal activities against T.ni were compared.[Result] Either the mixture of pure crystals and pure spores of 00-50-5 strain,or only pure crystals could kill T.ni larvae under the concentration of 100μg/mL after 48 h,and the mortality rate reached 100%;pure spores could not kill the larvae.Determination results of median lethal concentration showed that insecticidal activity of pure crystal of Bt 00-50-5 strain( LC50=0.32 μg/mL) was higher than the mixture of crystals and spores( LC50=0.48),but the insecticidal activity of pure spores was very low( LC50> 500.00).Therefore,the crystals were primarily responsible for causing death of larvae.[Conclusion] The paper provides theoretical basis for application of Bt 00-50-5 strain.