Lethal and sublethal effects of cycloxaprid,a novel cis-nitromethylene neonicotinoid insecticide,on the mirid bug Apolygus lucorum

Recently, Apolygus lucorum (Hemiptera: Miridae) has become an important insect pest of Bt cotton and fruit trees in China. At present, the application of chemical insecticides is the main control option for this pest. We investigated the lethal effect of seven neonicotinoid insecticides on A. lucorum adults, including six commercialized neonicotinoids and a novel one, cycloxaprid, which is developed in China. In addition, we assessed the sublethal physiological (longevity, fecundity) and behavioral (pre-oviposition and oviposition periods) effects of LD₁₀ (low lethal dose) and LD₄₀ (moderate lethal dose) of cycloxaprid on the mirid bug. Lethal effect of the insecticides was determined using a topical exposure method; contact toxicity against the adults was ranked as follows: cycloxaprid, nitenpyram > clothianidin > acetamiprid, imidacloprid > thiamethoxam > dinotefuran. Among these insecticides, the toxicity of cycloxaprid against the adults was the highest; its LD₅₀ value was 2.54 ng a.i. (active ingredient)/adult. Both LD₁₀ (0.74 ng a.i./adult) and LD₄₀ (1.98 ng a.i./adult) of cycloxaprid induced sublethal effects in the adults; we observed a reduced longevity in males and the LD₄₀ also shortened the longevity of females. In addition, the LD₄₀ prolonged the pre-oviposition period and shortened the oviposition period of females, and it decreased their fecundity. The hatching rate of eggs laid by the females exposed to LD₁₀ and LD₄₀ greatly decreased (two-fold lower when exposed to LD₄₀). Our results demonstrate that cycloxaprid is among the best candidate insecticides for controlling A. lucorum, and it showed significant lethal and sublethal effects on this mirid bug.