Toxicological Assessment of Neonicotinoid Acetamiprid Against the Confused Flour Beetle, Tribolium confusum Du Val (Coleoptera: Tenebrionidae)

Abstract

The confused flour beetle, Tribolium confusum, is a common insect that can be found in stores and homes and attacks a variety of commodities and stored foods. In the past, synthetic chemical insecticides were used to control them, which caused many negative health and environmental effects. Acetamiprid is a neonicotinoid insecticide with a novel mechanism of action, low toxicity for mammals, and a low environmental impact. The effectiveness of that insecticide against T. confusum was tested in this study. The toxicological bioassay was performed by contact application with different concentrations of acetamiprid. Our results indicated that the increased concentration and exposure periods significantly enhanced the mortality rate. The mortalities reached 20.6±1.12% and 92.6±1.86% at 1 ppm and 8 ppm concentrations of acetamiprid, respectively, after 14 days of exposure. The effects of acetamiprid on the fecundity and sterility of T. confusum have been assessed. Laboratory studies indicated that acetamiprid significantly reduced egg laying and hatching in comparison with the control. All acetamiprid concentrations used resulted in sterility in the treated adults. At the highest concentration (8 ppm), the sterility was 66.28%. The effects of acetamiprid on the activity of the acetylcholinesterase (AChE) enzyme were also investigated. It was observed that AChE from T. confusum was almost completely inhibited at the highest concentration. On the contrary, the level of the detoxifying enzyme, glutathione S-transferase, was increased in the treated samples. Acetamiprid's mutagenic effect on T. confusum was investigated by applying the median-lethal concentration (LC50), investigating DNA alteration for polymorphic numbers of genetic bands by using RAPD-PCR primers, and comparing it with the control. Results strongly suggest that acetamiprid causes mutagenic effects on T. confusum. The results recommended that acetamiprid can be used as a useful tool in pest management programs for T. confusum considering its insecticidal effects, which are evident at low applied concentrations and short exposure times. MATERIALS AND METHODS Insect Maintenance and Bioassay:A colony of Tribolium confusum was obtained from the laboratory of the Grains and Stored Product