Toxicities of 19 Acaricides to Tetranychus cinnabarinus and Their Safety Evaluations

Tetranychus cinnabarinu was one of the important pests of cotton in China.The damage of Tetranychus cinnabarinus to cotton plant was becoming serious as Bt cotton planted area increased in recent years.The management was commonly done based on repetitive application of acaricides.Some farmers used to apply high toxic acaricides,like organophosphate insecticides,or dicofol for Tetranychus cinnabarinus control.For environment safety and operators′health,high toxic insecticides would be banned in China sooner or later.Dicofol was also limited to be produced and applied because its intermediate DDT belonging to persistent organic pollutants(POPs).Screening alternative acaricides to high toxic organophosphate insecticides and dicofol for Tetranychus cinnabarinus was important for cotton production.Nineteen acaricides were evaluated in laboratory by slide-dip method against Tetranychus cinnabarinus occurred naturally in the suburb of Wuhan,Hubei Province in the summer of 2005.The results showed that the LC_(50) of abamectin to Tetranychus cinnabarinus was(0.0012) mg·L~(-1),with the best activity and should be applied for Tetranychus cinnabarinus control in cotton field as the first choice.The LC_(50) of fenproximate,pyridaben,emamectin and clofentezine to Tetranychus cinnabarinus were all below 1 mg·L~(-1),showed excellent toxicities and all can be applied for red spider control.The LC_(50) of spinosad,fenpropathrin and liuyangmycin were all below 20 mg·L~(-1),with better toxicities.The LC_(50) of bifenthrin,fenthion,dicolfol and amitraz were all below 50 mg·L~(1),and with good toxicities.Chloropyrifos,quinalphos,cyhalothrin,parathion and phosalone showed normal toxicities to Tetranychus cinnabarinus, and the LC_(50) were all above 100 mg·L~(-1).The analysis of the vertebrate selectivity ratio(VSR) of different acaricides showed that pyridaben,abamectin,clofentezine and fenproximate had very high selectivity against Tetranychus cinnabarinus.Liuyangmycin,spinosad and emamectin had high selectivity.Hexythiazox,propargite,dicolfol,amitraz,fenthion and fenpropathrin had better selectivity,and quinalphos,cyhalothrin,parathion and phosalone showed no selectivity to Tetranychus cinnabarinus.The influence of different acaricides against the natural enemy,microplitis mediator in the cotton field,were also studied and the results showed that abamectin,emamectine had the least effect.Based on the toxicity bioassay,relative toxicity index and VSR and its safety evaluation to natural enemy of this study,abamectin,emamectine,fenproximate,pyridaben,clofentezine,spinosad,fenpropathrin,bifenthrin,liuyangmycin and amitraz could apply for Tetranychus cinnabarinus control as alternatives to dicofol and high toxic organophosphate insecticides.