The susceptibility of onion thrips, Thrips tabaci Lind. (Thysanoptera: Thripidae) to different groups of insecticides

Onion thrips is a key pest of vegetable crops. Chemical control is a conventional controlmethod of onion thrips. The infested fields to onion thrips are usually treated several times each year. This study was conducted in the laboratory conditions to find the effective insecticides by using the filter paper bioassay. Cypermethrin EC10%, deltamethrin EC2.5%, diazinon EC60%, oxymatrine AS 0.6%, and spinosad (Tracer® SC240) were used in the bioassay. The filter papers were dipped in sequential concentrations of the insecticides The median lethal concentration (LC50) of insecticides was determined on 4 day-old adult thrips at 24 hours after treatments. The LC50 values of the insecticides were included 38.08, 3.08, 47.4, 2.43 and 4.8 a.i. μg/ml respectively. Oxymatrine and diazinon had the highest and lowest toxicity on T. tabaci respectively. Thus, oxymatrine can be considered as a new effective insecticide against onion thrips with low risk on environment and human.