Study On The Synergistic Effect And Synergistic Mechanism Of Spodoptera Exigua Nucleopolyhedrovirus On Chemical Pesticides

Spodoptera exigua is one of the main pests on asparagus,a characteristic cash crop in northern Zhejiang.Due to the gradual increase in resistance of beet armyworm in the field,the efficacy of most chemical pesticides has decreased,and its prevention and control have become more and more difficult.Spodoptera exigua Nucleo Polyhedro Virus（SeNPV）is an important pathogenic microorganism with application prospects.It can cause viral diseases in the host and is an important regulator of the population of Spodoptera exigua Nucleo Polyhedro Virus.At present,there is no report on the technology of using SeNPV and insecticides to control resistant beet armyworm at home and abroad.This study monitored the resistance levels of beet armyworm populations in asparagus plantations in northern Zhejiang to 11 insecticides,determined the synergistic effect of SeNPV on 11 insecticides,and evaluated emamectin benzoate and carbophenil.The field control effect of synergistic use with beet armyworm nuclear polyhedrosis virus,and further studies on the metabolic mechanism of the synergistic effect of beet armyworm on emamectin benzoate and tarfenile with beet armyworm nuclear polyhedrosis virus,related results It can lay the foundation for formulating scientific and reasonable control methods and resistance control measures of beet armyworm.The results of the study are as follows:1.The results of monitoring the resistance of beet armyworm in asparagus plantations in northern Zhejiang showed that the population of beet armyworm in Pinghu had the highest resistance to emamectin benzoate（43.58 times）,followed by spinetoram（17.88 times）,which was more effective.The most sensitive to chlorantraniliprole（1.21times）;the Tongxiang population of Spodoptera exigua has the highest resistance to chlorantraniliprole（22.57 times）,followed by indoxacarb（16.2 times）,and the most sensitive to cyantraniliprole（0.86 times）.The beet armyworm in the two places has a certain degree of resistance to emamectin benzoate,spinetoram,indoxacarb,tebufenil and chlorfluazuron,and to lufenuron,cyantraniliprole,and methoxafen,Hexaflumuron and spinosad are all at the sensitive level（<5 times）,and the sensitivity to chlorantraniliprole is decreased（4.00 times）and moderate resistance（22.57 times）respectively.Combining the use of pesticides in the asparagus bases in the resistance monitoring area,beet armyworms in the two places have developed resistance to spinetoram,indoxacarb,and tarenil,which have been used more frequently in the past two years.The drug-resistant emamectin benzoate did not restore the sensitivity of the drug due to the two-year discontinuation.2.The evaluation results of the synergistic activity of SeNPV on chemical insecticides showed that when the test insect object is the 3rd instar larva of the indoor population,the sublethal dose(LC₂₅)of SeNPV is against flufenuron and lufenuron The five insecticides,hexaflumuron,tarfenil,and spinetoram,have synergistic effects;when the test object is the 3rd instar larva of the Pinghu population,LC₂₅ SeNPV is effective against emamectin benzoate,carbofenil,and chlorfenarum.11 insecticides such as benzamide,cyantraniliprole,methoxyfenozide,chlorfluazuron,lufenuron,spinetoram,hexaflumuron,indoxacarb,and spinosad all have increased Effectiveness:When the test insects are the 3rd instar larvae of Tongxiang population,except for lufenuron and methoxyfenozide,LC₂₅ SeNPV has a synergistic effect on the other 9 insecticides.Regardless of whether the test insect is an indoor population or a field population,the sublethal dose(LC₂₅)of beet armyworm nuclear polyhedrosis virus has a synergistic effect on tefenuron,chlorfluazuron,hexaflumuron and spinetoram.3.The field test results of the synergistic use of SeNPV and two chemical insecticides showed that:LC₅₀ SeNPV+10%Tebufenil 900 m L/hm²（500 times）after treatment with 6 d and 10 d,the control effect reached 75.15%and 85.36%,respectively.,Compared with the control agent 10%Tebufenil 1800 m L/hm²（500 times）,it shows good persistence and insecticidal effect;LC₅₀ SeNPV（1.9×10⁷ PIB/m L）+Tebufenil（900m L/hm²）)（1000 times）treatment,3 d,6 d,and 10 d after treatment,the control effects were 64.49%,71.74%,and 80.48%,respectively.Compared with the control effects of61.50%,58.61%and 71.03%of the control agent,A 50%reduction in the use of tarfenil still maintains the control effect equivalent to that of the control agent,and the effect of reducing the drug and increasing the effect is obvious.In the mixed test of SeNPV and emamectin benzoate,LC₅₀ SeNPV+5%emamectin benzoate 900 g/hm²（1000 times）has the highest insecticidal activity,and the control effects of 3 d,6 d,and 10d after treatment are 64.58%and 60.36,respectively.%,80.64%;LC₂₅ SeNPV（9.9×10⁶ PIB/m L）+Emamectin benzoate（900 g/hm²）（1000 times）treatment and LC₅₀SeNPV（1.9×10⁷PIB/m L）+Emamectin benzoate（450 g/hm²）)（2000 times）treatment is also significantly higher than the control effect of 5%emamectin benzoate 900 g/hm²（1000 times）treatment,SeNPV also shows excellent drug reduction and synergistic effects.Experiments also show that because the field environment is more complex than indoors and has more influencing factors,the synergistic effect of the beet armyworm nuclear polyhedrosis virus on chemical insecticides is not linearly related to the concentration of the virus or insecticide in it.4.The effect of SeNPV,emamectin benzoate and carbofuran on the activity of detoxification enzymes in the larvae showed that:the synergist PBO has obvious antagonistic effect on carbofuran,DEM has a significant synergistic effect on emamectin benzoate,and TPP on insect Diclofenil has a significant antagonistic effect,but has a significant synergistic effect on emamectin benzoate;combined with emamectin benzoate and carbophenone to treat the changes in the specific enzyme activity of the larvae after a single dose,the analysis shows that the Pinghu population of beet armyworm is against The resistance of emamectin benzoate and carbofenil is related to changes in the activities of esterase and multifunctional oxidase respectively;it is speculated that the synergistic effect of SeNPV on emamectin benzoate may be due to the fact that the addition of SeNPV makes it impossible to be affected by the higher esterase activity.Emamectin benzoate directly kills the larvae;it is speculated that the synergistic effect of SeNPV on carbofenil may be due to the increase of multifunctional oxidase activity by SeNPV,which promotes the transformation of carbofenil and enhances its lethal activity;due to SeNPV Different from the lethal mechanism of pesticides,whether the metabolic mechanism of detoxification is the main mechanism of the synergistic effect of SeNPV on chemical pesticides remains to be further studied.