Sublethal Effect Of Cyetpyrafen On Panoychus Citri

Panonychus citri（Mc Gregor）（Acari:Tetranychidae）,the citrus red mite,is an economically important pest on citrus trees worldwide.At present,using chemical acaricides is still the main effective strategy of controling the citrus red mite.Cyetpyrafen is a newly commercialized acaricide developed by Shenyang Sinochem Agrochemicals R&D Company,Ltd to control tetranychid mite,and has excellent acaricidal activity.The sublethal effect of cyetpyrafen on P.citri and effects of multiple enzyme activities were studied in this paper.The research results are as follows:1.Laboratory bioassays were conducted to evaluate the toxicity of cyetpyrafen against egg,larva,nymph,and female adult of P.citri.The test results showed that after treatment of cyetpyrafen for 24 hours,the LC₅₀of eggs,larvas,nymphs,and female adults（leaf-residue method,residual contact）were 1.786 mg/L,0.264 mg/L,0.220 mg/L,0.267 mg/L,0466 mg/L;LC₁₀and LC₂₅for eggs and female adult mites（leaf residue method）are 0.552 mg/L,0.963 mg/L and 0.049 mg/L,0.110 mg/L,respectively.2.On the basis of laboratory bioassays,sublethal doses of LC₁₀and LC₂₅were used to treat eggs of P.citri,and the analysis of two-sex life table was used to study the sublethal effect of cyetpyrafen on P.citri eggs.The results showed that after treatment of eggs with sublethal dose of cyetpyrafen,the deutonymph stage of male mites was significantly longer than that of the control,but the longevity was significantly shortened（p<0.05）;Sublethal dose of cyetpyrafen has little effect on the development of female mites compared with the control,only the lifespan was significantly shortened.The TPOP（14.30 d,14.55 d）of LC₁₀and LC₂₅were significantly longer than that of the control（12.93 d）,and the oviposition period（6.20d,5.66 d）was significantly shorter than the control（7.19 d）,and the average oviposition per female（23.78 eggs/female,19.36 eggs/female）decreased by 9.61eggs/female and 14.03 grains/female compared with the control（33.39 eggs/female）.At the same time,the r（0.158,0107）,λ（1.171,1.113）,and R₀（15.21,9.17）of LC₁₀and LC₂₅were significantly lower than the r（0.194）λ（1.215）and R₀（22.82）in control,and significantly decreased with increasing concentration;the T of LC₁₀and LC₂₅were 17.20 and 17.77 d,significantly longer than the control（16.08 d）.3.Based on the theory of age-stage,two-sex life table,sublethal effect of cyetpyrafen treatment on female adults of P.citri on the development,reproduction and population dynamics of F₀and F₁generations.The results showed that after treatment with the LC₁₀and LC₂₅of cyetpyrafen,the longevity were shortened by 27.08%and 46.26%compared with the control,and the average oviposition per female were reduced by58.27%and 70.74%,respectively.The immature stage of females and males of F₁generation were significantly longer than that of the control,but the adult stage,oviposition period and the average oviposition per female are significantly lower.In addition,The r（0.145,0129）,λ（1.156,1.137）,R₀（12.22,5.59）,GRR（16.95,13.88）value of the F₁generation from the females treated with the LC₁₀concentration of cyetpyrafen were significantly reduced compared to the r（0.186）,λ（1.204）,R₀（20.44）and GRR（23.55）value of the control.4.Determination of the synergistic effects of piperonyl butoxide（PBO）,diethyl maleate（DEM）and triphenyl phosphate（TPP）with cyetpyrafen on females of the the citrus red mite.The results showed that the synergistic ratios of PBO,TPP and DEM were 2.47,1.21 and 0.92,respectively.5.In order to clarify the mechanisms of metabolism and detoxification of P.citri after exposure to sublethal doses of cyetpyrafen,the females of P.citri were treated with the LC₁₀and LC₂₅concentrations of cyetpyrafen for 6h,12h,24h and 48h,respectively.The activities of the carboxylesterase（CES）and glutathione-S-transferases（GSTs）and multifunctional oxidases（MFO）three detoxification enzymes and superoxide dismutase activity（SOD）,peroxidase（POD）,and catalase（CAT）three protective enzymes were determined.The results showed that different sublethal doses of cyetpyrafen had different effects on the activities of SOD,POD and CAT of P.citri.The activity of SOD has always been shown to be inducing after treated by LC₁₀concentration,but treated with the LC₂₅concentration it was induced at the early stage and then inhibited.The activity of POD was increased after exposed to sublethal concentrations of cyetpyrafen.The LC₁₀concentration of cyetpyrafen showed no significant effect on CAT activity,while the LC₂₅showed an effect of induction followed by inhibition.The effect of sublethal concentration of cyetpyrafen on the activity of CES,GSTs and MFO of P.citri were as follows:the LC₁₀concentration of cyetpyrafen on the activity of GSTs has no significant effect,while the activity after the LC₂₅concentration treatment was induced at the early stage and inhibited at the later stage;the activity of MFO and CES were inhibited after exposed to sublethal concentration of cyetpyrafen.