Insecticide Toxicity to Adelphocoris lineolatus (Hemiptera: Miridae) and its Nymphal Parasitoid Peristenus spretus (Hymenoptera: Braconidae)

Abstract

In China, Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) is an important pest of alfalfa, cotton, and other crops, while Peristenus spretus (Chen & van Achterberg) (Hymenoptera: Braconidae) is the dominant nymphal parasitoid of this mirid bug. In the present study, the toxicity of 17 common insecticides to A. lineolatus was evaluated, and the susceptibility of P. spretus to the insecticides with high toxicity to A. lineolatus was tested under laboratory conditions. Of the 17 insecticides tested, 12 (beta cypermethrin, deltamethrin, carbosulfan, acetamiprid, emamectin benzoate, imidacloprid, phoxim, chlorpyrifos, acephate, profenophos, hexaflumuron, and abamectin) had a highly toxic effect on second-instar nymphs of A. lineolatus, with LC(50) values ranging from 0.58 to 14.85 mg a.i. (active ingredient) liter(-1). Adults of P. spretus were most sensitive to chlorpyrifos, with LC(50) values of 0.03 mg a.i. liter(-1), followed by phoxim, acetamiprid, profenophos, carbosulfan, acephate, deltamethrin, emamectin benzoate, imidacloprid, beta-cypermethrin, and abamectin, with LC(50) values ranging from 0.06 to 3.09, whereas hexaflumuron exhibited the least toxicity to the parasitoid, with LC(50) values >500 mg a.i. liter(-1). A risk quotient analysis indicated that beta-cypermethrin, emamectin benzoate, abamectin, and hexaflumuron when applied against A. lineolatus were the least toxic to P. spretus.

Keywords: acute toxicity; mirid bug; parasitoid; risk assessment.