Sublethal Effect Of Tolfenpyrad On Chrysoperla Sinica

Chrysoperla sinica is an important predatory natural enemy insect in China,which can prey on the eggs of various pests such as aphids,thrips and various lepidopteran pests,and has great application value in biological control.Chemical control is the main method for pest control in China at present.The application of insecticides will not only cause lethal effects on target pests,but also affect non-target organisms such as predatory natural enemies insects to varying degrees.In order to understand the acute toxicity and sub-lethal effect of tolfenpyrad on C.sinica larvae,the acute toxicity of tolfenpyrad to C.sinica larvae was determined by the drug film method in this study,and the effects of the three sublethal concentrations on the growth and development of lacewing,population quantity and fertility,as well as the feeding ability of the 2nd instar larvae of the lacewing were determined.A series of physiological and biochemical indexes and the activities of related enzymes were determined.The main research results are as follows:1.The toxicities of tolfenpyrad against the 2nd instar larvae of the lacewing were determined by means of the dactyl-tube drug film method,and the LC₅₀ value was 54.66mg/L.Three sublethal concentrations of LC₁₀,LC₂₀ and LC₃₀ were determined to understand the sublethal effects of tolfenpyrad on C.sinica larvae,and the three sublethal concentrations were 3.84 mg/L,9.56 mg/L and 18.45 mg/L,respectively.2.The results showed that the pupation rate,pupal weight,pupal emergence rate,adult survival rate and egg hatching rate of lacewings were significantly decreased under the three sublethal concentrations of tolfenpyrad LC₁₀,LC₂₀ and LC₃₀.The pupal period and larva duration was significantly prolonged.The number of eggs laid per female was 949.65±27.15under LC₁₀ concentration,which was 10.74%higher than that of 857±21.57 in control group.However,the concentration of LC₂₀ and LC₃₀ decreased significantly,the number of eggs laid per female in LC₂₀ treatment group was 661.05±43.95,which was 22.86%lower than that in control group;the number of eggs laid per female in LC₃₀treatment group was 596.9±35.78,which was 30.35%lower than that of the control group.The number of eggs laid female daily during the eclosion period from emergence to death was recorded,compared with the control group,the oviposition peak of lacewing treated with three sublethal concentrations was earlier than that of the control group.In LC₂₀ and LC₃₀ treatment groups,the maximum number of eggs laid female daily and the oviposition duration was decreased or shortened,while in LC₁₀treatment group,the maximum number of eggs laid female daily was decreased,but the oviposition duration was significantly prolonged,and there was no significant effect on the survival rate of lacewing larvae.3.The predation quantity and predation rate of lacewing was decreased,and the searching effect also was decreased to different degrees under the three sublethal concentrations of tolfenpyrad LC₁₀,LC₂₀ and LC₃₀.When the aphid density is 20 head/dish,the predation quantity of lacewing in LC₁₀ treatment group was decreased,but the difference was not significantly compared with the control group;other treatment groups,under the condition of different density of aphid,the concentration of each treatment was significantly different from that of control group.Lacewing feeding function reaction model does not change,and is still the HollingⅡreaction model.Compared with the control group,transient attack rate was decreased by 64.89%,48.95%and 8.8%after the treatment of three sublethal concentrations LC₃₀,LC₂₀ and LC₁₀ treatment,respectively.The processing time of prey was increased by 0.56,1.69 and 1.71 times,respectively.In addition,the maximum theoretical predation quantity was reduced by 10.55%,62.79%and 63.07%,respectively.4.Determination of reactive oxygen species（ROS）,malondialdehyde（MDA）levels of change and protective enzyme,detoxification enzyme activity change,and the target enzyme and ATP energy synthesis,lacewing larvae of ROS and MDA content as a whole has a tendency to increase,at the same time,the levels of ROS and MDA was increased with the increase of tolfenpyrad concentration,and the accumulation of ROS and MDA was increased with the prolongation of time also.At the same time,the activities of three detoxification enzymes and protective enzymes were significantly increased compared with the control group,and had a certain time effect.With the prolongation of time,the activities increased gradually.ATP content and mitochondrial respiratory chain complexⅠcontent all have different degrees of lower at different periods,compared with the control group.In dealing with 2 days,4 days,5 days,LC₂₀concentration treatment group MRCCⅠand ATP content were the lowest,and began to fell sharply in 4 days after treatment.In conclusion,the sublethal concentration of tolfenpyrad significantly affected the growth and development,population quantity and predation capability of the lacewing,and caused the accumulation of substances such as reactive oxygen species and malondialdehyde in the lacewing larvae,which induced the increase of the activities of protective enzymes and detoxification enzymes,and caused some oxidative damage to the lacewing.In addition,italso inhibited the activity of tolfenpyrad target enzyme and the synthesis of ATP during mitochondrial respiration,and the synthesis of ATP during mitochondrial respiration was affected,which reduced the body’s energy supply and affected the normal life activities of the lacewing.