Effects of spirodiclofen on activity and efficacy of Tetranychus viennensis

Key Words： spirodiclofen, Tetranychus vinnensis, fecundity, activity, rate of decrease

Abstract：      Spirodiclofen (SC) is an efficient, low toxicity and broad-spectrum acaricide. In order to study the effectiveness of spirodiclofen in controlling Tetranychus vinnensis, eggs, immature and adults of this mite were treated with a range of concentrations of 24%SC. The results show that spirodiclofen was most efficient at killing eggs and nymphs; the LC50 of these life stages was 0.76 mg/L and 19.07 mg/L respectively. The corrected mortality rates of adult mites treated by slide-dipping with 48, 96 and 192 mg/L of spirodiclofen were 2.6%, 19.4% and 19.4% after 48 h exposure. Female fecundity and fertility was significantly reduced when they were sprayed directly with concentrations of 1.5, 3, 6, 12, 24 and 48 mg/L. In a glasshouse trial, mite numbers were reduced by 100% 21 days after treatment with 60 mg/L of spirodiclofen. This was much more effective than the 33.3% reduction observed following treatment with 250 mg/L of clofentezine. In conclusion, spirodiclofen was most toxic to eggs and nymphs of T. vinnensis. Although adult females were less susceptible，their fecundity and fertility were significantly reduced. We therefore recommend the application of this pesticide for controlling mites in orchards. It is particularly suitable for spraying during the egg-stage of the first generation.