Insecticidal efficacy of spinetoram against Sitophilus zeamais : Influence of dose, exposure interval and temperature

摘要

The efficacy of spinetoram against Sitophilus zeamais adults was investigated using nine dose rates, 0.01, 0.10, 0.25, 0.50, 0.75, 1.00, 2.00, 5.00 and 10.00 mg kg(-1) at 20, 25 and 30 degrees C (55% r.h) in the laboratory. Mortality was assessed 1, 2, 3, 7, 14, 21, and 28 d after exposure, and progeny production was recorded 65 d after the final count. Dose rates and exposure periods affected adult mortality, while temperature did not in most of the exposure period-dose combinations. At low doses of 0.50 mg kg(-1), mortality rates did not reach 50%, despite increasing exposure periods. Complete mortality was achieved at 2 mg kg(-1) at 30 degrees C, and at > 5 mg kg(-1) at 20 and 25 degrees C after 28 d exposures. Generally, significant increase in mortality were observed at > 7 d exposures. However, at 30 degrees C the mortality rate reached 51% after 2 d exposure to 10 mg kg(-1). Increasing the temperature to 30 degrees C had a significant effect in decreasing the dose rates for insect mortality. Significant reductions in progeny development were obtained at > 2 mg kg(-1) at 20 and 25 degrees C, and at > 1 mg kg(-1) at 30 degrees C. The difference in temperature, with the exception of 1 and 2 mg kg(-1) dosages, had no effect on reducing the progeny. In light of the mortality and progeny data, we can conclude that spinetoram can successfully control S. zeamais and suppress its population growth by decreasing progeny production. (C) 2020 Elsevier Ltd. All rights reserved.