Abstract: In order to develop a new agent of Lecanicillium lecanii to control pests on vegetable, the crude toxin of Lecanicillium lecanii JMC-01 fermented for eight days was extracted by ethyl acetate, with which the apterous Myzus persicae and 3rd instar larvae of diamondback moth (Plutella xylostella) were treated. We measured the indoor virulence of the test insects and the changes of glutathione S-transferase (GST), carboxylesterase (CarE), acetyl cholinesterase (AchE) and peroxidase (POD) activities of the test insects. The results showed that the toxicity of JMC-01 crude toxin to M. persicae and P. xylostella reached 94.25% and 85.41%, and the LC₅₀ values were 37.62 and 43.42 mg·L^-1, respectively. After being treated with JMC-01 crude toxin, the activities of CarE, AchE, GST, and POD in M. persicae increased to 0.81, 0.1173, 22.52, and 5.29 U·mg^-1 prot, respectively, while those of P. xylostella increased to 0.85, 0.1176, 27.5, and 13.25 U·mg^-1 prot, respectively. Our results demonstrated that the JMC-01 crude toxin contained natural insecticidal active substances by examining the virulence of the crude toxin to M. persicae and P. xylostella, as well as the changes of detoxification enzyme and protective enzyme activities, which provided basis for the further development of fungal biocontrol agents.

Key words: Lecanicillium lecanii, crude toxin, pathogenicity, enzyme activity.