Effects of soil-treatment with fungal biopesticides on pupation behaviors, emergence success and fitness of tea geometrid, Ectropis grisescens (Lepidoptera: Geometridae)

Abstract Ectropisgrisescens Warren (Lepidoptera: Geometridae) is one of the most severe defoliating pests of tea plants. Synthetic pesticides have been widely applied to control this pest in tea plantations, but pesticide residues may decrease the quality and safety of tea products. In the present study, we hypothesized that soil treatment with the two commercial biopesticides (Shuiguxin ® ) based on Metarhizium anisopliae (Metchnikoff) Sorokin and Beauveria bassiana (Balsamo) could reduce the survivorship and fitness of E. grisescens . Wandering larvae of E. grisescens were allowed to pupate in soil treated with each biopesticide, and the concentrations of M. anisopliae (Shuiguxin ® ) and B. bassiana (Shuiguxin ® ) that produced the 50% mortality values (LC 50 ) were 2.9 × 10 6 and 1.6 × 10 7 conidia/g soil, respectively. Artificial burying the pupae using soil treated with M. anisopliae (Shuiguxin ® ) and B. bassiana (Shuiguxin ® ) (1 × 10 8 or 1 × 10 9 conidia/g soil for both biopesticides) also significantly reduced emergence success of E. grisescens . In addition, choice tests showed that soil treated with the high concentration of M. anisopliae (Shuiguxin ® ) or B. bassiana (Shuiguxin ® ) had repellent effects on pupating E. grisescens. However, sublethal concentrations (LC 25 and LC 50 ) of both biopesticides did not significantly affect fecundity, fertility and longevity of post-emerged adults. Our study showed that soil treatment with the two commercial biopesticides caused direct mortality of pupating E. grisescens , but may not effectively suppress E. grisescens populations at sublethal concentrations. The realistic application of the fungal dosage in fields should be determined in future studies