Resistance and Susceptibility to Several Groups of Insecticides in the Small Brown Planthopper,Laodelphax striatellus(Homoptera: Delphacidae)

The resistance to nine insecticides and the sensitivity to seventeen insecticides were evaluated in two field populations of the small brown planthopper(SBPH),Laodelphax striatellus Fallen,collected from Wuxi City,Jiangsu Province and Huzhou City,Zhejiang Province in April 2006.The results detected by topical application showed that Wuxi and Huzhou populations developed high level resistance to imidacloprid(79.6-fold and 44.6-fold),and propoxur(76.6-fold and 40.1-fold),mid-high level resistance to carbaryl(29.8-fold and 45.3-fold),respectively,and remained susceptible or low level resistance to diazinon,fenitrothion,fenobucarb,carbosulfan,etofenprox and fenvalerate(1.4-to 8.1-fold).The assay on toxicities of the 17 insecticides to the third instar nymphs of Wuxi and Huzhou populations by using rice stem dipping method showed that the toxicity of fipronil and butylene-fipronil to SBPH was the highest,with the LC50 values being 0.21-0.41 mg/larva,and the recommended insecticides of field efficacy trial were thiamethoxam,nitenpyram,chlorpyrifos,pymetrozine,isoprocarb and dichlorvos.Furthermore,the resistance management strategies of the small browm planthopper to insecticides were also discussed.