Abstract: To scientifically utilize biocides and conserve natural enemies for integrated control of Helicoverpa armigera, the bioefficacy of a mixed biocide BtA in comparison with seven commercial insecticides (abamectin, Bt toxin, beta-cypermethrin, phoxim, chlorfluazuron, fenvalerate and carbosulfan) against H. armigera and its contact toxicity to pupae and female adults of parasitoid Microplitis mediator were bioassayed in the laboratory and compared. Toxicity of these compounds on the 3rd instar larvae of H. armigera by leaf dip bioassays within 72 h in the laboratory showed that BtA had high toxicity (LC₅₀ = 0.7364 mg/mL) in comparison with the other commercial insecticides. Mortalities of the 3rd instar larvae of H. armigera exposed to Brassica rapa var. pekinensis treated with 4 mg/mL of these compounds were significantly different at 24, 48, and 72 h in pot trials (P≤0.05). BtA had no significantly different bioefficacy (P>0.05) in the experimental pots from the other commercial insecticides against H. armigera larvae at 72 h after treatment. After application of BtA, larval mortality of H. armigera increased as time extended. Bioassay of the contact toxicity of these compounds to pupae and female adults of parasitoid M. mediator showed that BtA has low toxicity to pupae and female adults of M. mediator, with the mortality values of 13.82% and 7.33%, respectively, in comparison with fenvalerate and carbosulfan. We so concluded that BtA has a moderate toxicity to the lepidopterous pest, H. armigera, and a relatively low toxicity to its parasitoid, M. mediator.

Key words: Helicoverpa armigera, Microplitis mediator, insecticides, biocide, BtA, toxicity, contact toxicity