DISRUPTION OF HOST-SEEKING RESPONSE OF FEMALE SCLERODERMA SICHUANENSIS TO Y-TUBE OLFACTOMETER INDUCED BY EMAMECTIN BENZOATE AND MATRINE

Abstract

Scleroderma sichuanensis is an ectoparasitoid wasp used in the biological control of wood-boring beetles. This study examines the sublethal effects of three insecticides-emamectin benzoate and matrine on the host-seeking behavior of female S. sichuanensis. The wasps were exposed to LC₂₀ concentrations of each insecticide and then evaluated in a Y-tube olfactometer to assess their olfactory responses, learning, and memory using synthetic host compounds from Monochamus alternatus at concentrations of 500, 100, and 10 mmol/L. Exposure to emamectin benzoate led to a reduction in host-selection rates to 61%, 51%, and 52% at concentrations of 500, 100, and 10 mmol/L, respectively. In contrast, matrine decreased selection rates to 57%, 33%, and 51%, respectively, when compared to the control. Regarding natural host cues, emamectin benzoate produced selection rates of 76% for larval hemolymph and 60% for pupal odor, while matrine resulted in 67% and 77%, respectively. Both insecticides also influenced olfactory learning and memory; wasps exposed to emamectin benzoate exhibited selection rates of 60%, 62%, and 51% during the learning phase, and 56%, 37%, and 37% during memory evaluation. Conversely, matrine-exposed wasps demonstrated selection rates of 57%, 40%, and 50% during learning, and 60%, 40%, and 43% during memory assessment. These results suggest that sublethal exposure to emamectin benzoate and matrine can moderately impair host-seeking behavior, olfactory learning, and memory in S. sichuanensis, which may impact on its efficacy as a biological control agent. Consequently, it is essential to carefully evaluate the use of these insecticides in integrated pest management strategies that involve S. sichuanensis for biological control.