Assessment of relative toxicity of insecticides to the green plant bug,Lygus lucorum Meyer-Dr(Hemiptera:Miridae),by two different bioassay methods

The economic importance of the green plant bug,Lygus lucorum Meyer-Dr,has become prominent in area where transgenic Bt cotton are widely planted in China. Controlling of green plant bugs relies mainly on insecticides,and chemical control is one of the important strategies used in IPM. This study was designed to assess acute contact toxicities of conventional and novel insecticides to green plant bugs by two different bioassay methods including glass-vial and topical application. Thirty insecticides,including organochlorines,organophosphates,pyrethroids,carbamates,nereistoxins,neonicotinoids,phenylpyrazoles,antibiotics,insect growth regulators (IGRs),and botanical insecticides were selected to investigate their toxicities against adult green plant bugs. Median lethal concentrations (LC50) of some insecticides were first determined by the two methods. The results showed that in laboratory bioassays,general insecticides including organochlorines,organophosphates,carbamates and pyrethroids were highly toxic to adult green plant bugs. Five (malathion,chlorpyrifos,bifenthrin,methomyl and endosulfan) of eight most toxic insecticides on the bugs among all the test chemicals were general insecticides. Novel insecticides phenylpyrazole showed the highest acute contact toxicity,of which fipronil had the highest toxicity to green plant bugs. The LC50 values of fipronil by two bioassay methods were 0.13 and 0.15 mg·L-1,respectively. IGRs,antibiotics and botanical insecticides,however,had no obvious acute contact toxicity to adult green plant bugs.