Sublethal Effect Of Triflumezopyrim On The Small Brown Planthopper (Laodelphax Striatellus Fallén)

The small brown planthopper?Laodelphax striatellus?belongs to the Homoptera,Delphacidae.It is the main pest on rice in China and Southeast Asia.With the application of triflumezopyrim,a new type of dielectrical agent developed by DuPont,its control effect and impact on L.striatellus need to be evaluated urgently.In this study,the toxicity of triflumezopyrim to the L.striatellus population in six areas of Shandong Province was determined by rice seedlings dipping method and topical application method.The effects of sublethal doses of triflumezopyrim(LD₁₀,LD₂₀ and LD₃₀)on the reproduction and the activities of esterase?EST?,glutathione-s-transferase?GST?and mixed-function oxidase?MFO?of the L.striatellus were elucidated.Female fecundity and longevity of F₀ and F₁generations of the L.striatellus were forced to change,and life tables of F₁ generation were established.The main results are as follows:The results of rice seedlings dipping method showed that the highest sensitivities showed that the highest sensitivities 3rd instar nymphs and adults to the triflumezopyrim were 0.77580.7517 mg/L,respectively,and the lowest were 1.6435 1.0757 mg/L,respectively.The results of the topical application method showed that the LD₅₀ value of triflumezopyrim to the 3^rdd instar nymphs of the 6 populations of the L.striatellus was between 3.4866×10^-4?g/insect to7.4412×10^-4?g/insect;the toxicity to adults was between 1.9472×10^-4?g/insect to4.1956×10^-4?g/insect.The results showed that triflumezopyrim showed good indoor activity against 6 populations of L.striatellus in Shandong Province.Sublethal doses of triflumezopyrim(LD₁₀,LD₂₀ and LD₃₀)affected activities of three detoxification enzymes of L.striatellus.The enzyme activities of EST and GST showed a trend of decreasing first and then increasing,which showed inhibitory effect.However,MFO enzyme activity showed an obvious upward trend at 24h and 48h after treatment,with an obvious induction effect.The results showed that MFO may be the main detoxifying enzyme in the detoxification metabolism of triflumezopyrim by L.striatellus and play a major role in the subsequent resistance formation.The results of sub-lethal test of triflumezopyrim on the L.striatellus showed that the oviposition of F₀ generation females of the three treatments decreased by 6.78%,14.50%and30.26%respectively compared with the control group.After treatment with triflumezopyrim,the development duration of F₁ generation was prolonged to varying degrees,and the fecundity?Fd?decreased by 6.9%,18.1%and 28.0%,respectively.In addition,the predicted predicted progeny number?N?and population trend index?I?are lower than those of the control,and the relative fitness of the populations of L.striatellus in the LD₁₀,LD₂₀ and LD₃₀concentration treatment groups are only 0.82,0.73 and 0.57,respectively,indicating that the sublethal concentration of triflumezopyrim can effectively inhibit the population growth of L.striatellus.The results showed that the use of triflumezopyrim not only had better control effect,but also had sub-lethal effects,such as prolonged generation cycle,changes in detoxification enzyme activity,decreased fecundity,prolonged longevity and slowed population growth.