The Response And Metabolic Resistance Of Tetranychus Urticae To Sublethal Concentrations Of Bifenazate And B-azolemiteacrylic

The two-spotted spider mite,Tetranychus urticae Koch,is a worldwide pest mite with a wide range of hosts,strong pesticides resistance and fast reproduction speed,which has caused serious economic losses to agricultural production.At present,chemical control is still the main strategy for managing this spider mite in China,and evaluating the sublethal effects of pesticides on mites is helpful to selecte safer and more efficient agents and to provide a guidence for rational use of pesticides.Therefore,this paper mainly discusses the toxicity and sublethal effects of B-azolemiteacrylic and bifenazate on T.urticae,to evaluate the effect of the sublethal dose of B-azolemiteacrylic and bifenazate on the population of T.urticae,in order to reveal the mechanism of metabolic resistance of T.urticae to these two agents,and provide a theoretical basis for its scientific and rational use.The main research contents and results are as follows:1.Toxicity of B-azolemiteacrylic and bifenazate to T.urticaeThe leaf dipping method was used to measure the virulence of the female adults of T.urticae treated with different concentration gradients of B-azolemiteacrylic and bifenazate,respectively.The virulence regression equation was fitted and the sublethal concentrations were calculated.The results showed that after 48 hours of B-azolemiteacrylic treatment,the virulence regression equation was y=0.99+1.11x,R²=0.991,LC₅₀ was 0.127 mg/L,LC₄₀,LC₃₀,LC₂₀ and LC₁₀ were 0.139,0.072,0.033 and 0.011 mg/L respectively.After 48 hours of bifenazate treatment,the virulence regression equation was y=-0.71+0.99x,R²=0.992,LC₅₀0 was 5.251 mg/L,LC₄₀,LC₃₀,LC₂₀ and LC₁₀ were 4.091,2.264,1.133 and 0.434 mg/L,respectively.2.Effects of sublethal concentration of B-azolemiteacrylic and bifenazate on the development and reproduction of F₀ generation of T.urticaeThe effects of sublethal doses LC₁₀ and LC₃₀ of B-azolemiteacrylic and bifenazate on F₀ generation of T.urticae were determined by leaf disc method.The results showed that the life span and oviposition period of female adults treated with B-azolemiteacrylic(LC₁₀ and LC₃₀)were 20.29d,19.42d and 8.95d,8.05d,which were 13.40%,17.11%and 21.90%,29.76%shorter than that of the control,respectively.The average total oviposition per female and the average daily oviposition per female were 52.58d,46.26d and 5.89d,5.65d,respectively,which were 30.93%,39.24%and 11.69%and 16.64%decreased than that of the control,respectively.After treatment with bifenazate(LC₁₀ and LC₃₀),the life span and oviposition period were 19.47d,18.42d and 8.59d,7.92d,respectively,which were 16.9%,21.38%and 25.04%,30.89%shorter than the control.The average total oviposition per female and the daily oviposition per female were 51.29d,47.17d and 6.04d,5.75d,respectively,which were 32.63%,38.04%and 9.45%,13.79%decreased than the control.The hatching rate and the female-to-male ratio of F₁ generation were significantly reduced treated with these two acaricides.The results showed that the sublethal doses of B-azolemiteacrylic and bifenazate inhibited the growth,development and reproduction of female adults of T.urticae.3.Effects of sublethal concentration of B-azolemiteacrylic and bifenazate on the life table parameters of F₁ generation of T.urticaeThe effects of sublethal doses of B-azolemiteacrylic and bifenazate on the population developmental duration and fecundity of the F₁ generation of T.urticae were measured.The results showed that after treated with sublethal doses LC₁₀ and LC₃₀ of B-azolemiteacrylic,the developmental duration of larva,adult,average life span and oviposition period of F₁generation were significantly shorter than that of the control?P<0.05?.The population trend index and disturbance effect control index of LC₁₀ and LC₃₀ treatments were 37.98,30.37and 0.84,0.77,respectively,while the controls were 55.13 and 1.00,respectively.After treated with sublethal doses of bifenazate LC₁₀ and LC₃₀,the larva stage was significantly longer than that of the control?P<0.05?.The developmental duration of protonymph,deutonymph of LC₃₀0 treatment,adult,average life span and oviposition period were significantly shorter than that of the control?P<0.05?.The population trend index and disturbance effect control index of LC₁₀ and LC₃₀ treatments were 38.91,30.15 and 0.80,0.75,respectively.After treatment with these two acaricides,the oviposition amount per female was significantly reduced?P<0.05?,and the population trend index and the disturbance effect control index were smaller than the control.It is suggested that the population quantity and population density of T.urticae treated with the sublethal doses of B-azolemiteacrylic and bifenazate will reduce in the next generation.At the same time,the life tables of F₁ generation of T.urticae treated with B-azolemiteacrylic and bifenazate at sublethal dosages were established.The results showed that the net reproductive rate?R₀?,intrinsic rate of increase?r_m?and finite rate of increase???of F₁ generation of T.urticae treated with sublethal doses of these two acaricides were decreased than the control,the average generation cycle?T?was significantly shortened.The population doubling time?D_t?of T.urticae population treated with B-azolemiteacrylic and bifenazate was 2.9903,3.2466 and 3.0006,3.2866,respectively,which were longer than the control population of 2.7660.The results showed that the sublethal doses of B-azolemiteacrylic and bifenazate could reduce the development and reproduction rate of T.urticae population and significantly inhibit the growth of F₁ generation population.4.Effects of sublethal concentration of B-azolemiteacrylic and bifenazate on the specific activity and enzyme kinetic constants of detoxification enzymes of T.urticaeDetermination of the specific activities,Michaelis constant?K_m?and Maximal Velocity(V_max)of glutathione s-transferase?GSTs?,carboxylesterase?care?and multifunctional oxidase?MFO?of T.urticae treated with B-azolemiteacrylic and bifenazate LC₁₀ and LC₃₀.The results showed that the specific activities of CarE and MFO of T.urticae treated with B-azolemiteacrylic and bifenazate sublethal doses(LC₁₀,LC₃₀)were increased within 6 to60 hours,for the activation.The specific activity of GSTs was higher than that of the control except LC₁₀ treatment of B-azolemiteacrylic at 12h,24h and LC₁₀ treatment of bifenazate at24h.The specific activity of GSTs?except 36h and 48h?,CarE and MFO?except 24h and60h?under LC₃₀ treatment of B-azolemiteacrylic were significantly higher than that of LC₁₀.The specific activity of GSTs?except 48h?,CarE and MFO?except 36h?under LC₃₀treatment of bifenazate was also significantly higher than that of LC₁₀.The results showed that the detoxification enzyme of T.urticae was induced by B-azolemiteacrylic and bifenazate,the higher concentration of the agent,the greater induction,and the magnitude of induction also varies at different times.In the study of enzyme kinetics,after the T.urticae treated with sublethal dose of B-azolemiteacrylic and bifenazate,compared with the control,the K_m value of CarE decreased and the V_max value increased,while the K_m value of GSTs and MFO were increased and the V_max value was decreased,which indicated that the CarE had the strongest affinity with the substrate and the fastest reaction rate.Which indicated that CarE played a key role in the detoxification metabolism of B-azolemiteacrylic and bifenazate against T.urticae.