Study On The Control Of Tetranychus Urticae On Strawberry Through The Integration Of Phytoseiulus Persimilis And Acaricides

The two-spotted spider mite,Tetranychus urticae Koch（Acari:Tetranychidae）is an important economic pest of agricultural and horticultural plants all over the world.It damages a variety of crops,vegetables,fruit trees,flowers,etc,causing huge economic loss to agricultural production.In recent years,the occurrence and harm of T.urticae on strawberry showed an increasing trend,which seriously affected the production of strawberry.With the development of green agriculture,in order to effectively control pest mites and reduce the use of chemicals,the combined application of predatory mites and acaricides provides a new idea for comprehensive treatment of T.urticae on strawberry,and the success of the joint control depends to some extent on their compatibility.Therefore,this paper starts from the perspective of joint control,the acute toxicity of six acaricides to T.urticae（pest mites）and Phytoseiulus persimilis（predatory mites）was evaluated in laboratory,and the most representative acaricide was selected.The effects of the median lethal concentration(LC₅₀)of chemicals on predation of P.persimilis and the effect of feeding medicated prey on the F₀and F₁generation of P.persimilis were determined,and the safety of cyetpyrafen on two pollinators insects（Apis mellifera ligustica and Bombus terrestris）was evaluated.The control effects of three control methods on T.urticae on strawberry were compared through pot experiment and field experiments.From the perspective of reducing application dosage and effectively controlling pest mites,this study is expected to provide a theoretical basis for joint control and provide a reference for the use of pollinating insects in protected agricultural environment.The main results are as follows:1.The acute toxicity of six kinds of acaricides to female adult mites of T.urticae was determined.The results show that the order of acute toxicity within 24 hours of six acaricides was:cyetpyrafen>cyflumetofen>bifenazate>diafenthiuron>spirodiclofen>etoxazole.The order of acute toxicity of ethoxazole within 48 hours was:cyetpyrafen>cyflumetofen>bifenazate>diafenthiuron>spirodiclofen>etoxazole,indicating that cyetpyrafen has the strongest toxicity to female adult mites of T.urticae within 24 hours and 48 hours,and etoxazole has the lowest toxicity to female adult mites of T.urticae.2.The acute toxicity of six kinds of acaricides to female adult mites of P.persimilis was determined.The results show that the order of acute toxicity within 24 hours of six acaricides was:cyflumetofen>cyetpyrafen>etoxazole>bifenazate>spirodiclofen>diafenthiuron.The order of acute toxicity of ethoxazole within 48 hours was:cyflumetofen>cyetpyrafen>diafenthiuron>etoxazole>bifenazate>spirodiclofen,indicating that among the six acaricides,cyflumetofen had the highest toxicity to the female adults of P.persimilis within24 hours,while diafenthiuron had the lowest toxicity to the female adults of P.persimilis,the toxicity of diafenthiuron to the female adults of P.persimilis was the highest within 48 hours,while that of spirodiclofen was the lowest.3.The selective toxicity index of six kinds of acaricides against T.urticae and P.persimilis showed,the TSR value of cyetpyrafen was the highest,indicating that cyetpyrafen was highly toxic to T.urticae,but relatively safe to P.persimilis.4.According to the application sequence in the field,the effect of on the predation of P.persimilis with the median lethal concentration(LC₅₀)of cyetpyrafen in laboratory,the results show that the application of cyetpyrafen followed by release of mites has a significantly greater effect on P.persimilis predation than application of cyetpyrafen followed by release of mites Mites have no significant effect compared to controls,suggesting that cyetpyrafen before the release of mites has little effect on P.persimilis predation.5.According to the two-sex life table theory,the effects of the median lethal concentration(LC₅₀)of cyetpyrafen on F₀and F₁generations of P.persimilis were studied.The results showed that the longevity of the F₀generation of P.persimilis was not significantly affected by feeding T.urticae treated with the median lethal concentration(LC₅₀)of cyetpyrafen,but the fecundity was reduced,the effect on F₁generation is small and does not affect population growth.6.The acute toxicity and risk assessment of cyetpyrafen to Apis mellifera ligustica and Bombus terrestris were studied by feeding and contact methods.The results showed that there was no death of A.m.ligustica and B.terrestris was caysed by cyetpyrafen within 48 h,even when the upper limit test was reached.According to the classification of pesticide toxicity to bees,cyetpyrafen was judged to be low toxicity to A.m.ligustica and B.terrestris.According to the environmental risk assessment,cyetpyrafen was judged to be low risk and acceptable.7.The results of pot and field experiments showed that the chemical control,biological control,joint control had a certain inhibitory effect on the population density of T.urticae on strawberry,joint control had the advantages of fast chemical control and long biological control.Therefore,when the population density of T.urticae is high in the field,in order to reduce the dosage and quickly control T.urticae,first reduce the population number with low-dose cyetpyrafen,then release P.persimilis the next day for control.