高浓度氯虫苯甲酰胺苗期喷雾在甜玉米叶片中的残留时空分布及对草地贪夜蛾的防治效果评价OA

[Aim]To clarify the residue distribution of high-concentration chlorantraniliprole in leaves of sweet corn seedlings at the transplanting stage using the"insecticide-treated seedling transplanting"technique and its insecticidal efficacy against the fall armyworm,Spodoptera frugiperda.[Methods]This study simulated the"insecticide-treated seedling transplanting"treatment by conventional spraying.The leaves from the upper,middle and lower parts of sweet corn plants were collected at 3,7,14 and 21 d after application.The residue dynamics of chlorantraniliprole at different leaf positions were determined using liquid chromatography-tandem mass spectrometry(LC-MS/MS).On this basis,the susceptible baseline of the laboratory susceptible population of S.frugiperda to chlorantraniliprole residue was established using the leaf-dip method,and the insecticidal efficacy of chlorantraniliprole residues in leaves against the F,larvae of the field population of S.frugiperda was assessed using in vitro leaf feeding method,thereby establishing the correlation between chlorantraniliprole residues and corrected larval mortality.Field plot trials were conducted in Nanning,Guangxi,southern China in August 2024 and March 2025,the proportion of damaged corn plants was investigated using the whole-field direct observation method,and the control efficacy of chlorantraniliprole against S.frugiperda at different time after application was calculated to evaluate the practical effectiveness of this technique.[Results]Chlorantraniliprole residues in sweet corn leaves at different positions displayed a clear distribution pattern,with higher residues in lower leaves and lower residues in upper leaves of sweet corn seedlings.From 3 to 21 d after application,the residues of the active ingredient of chlorantraniliprole in lower corn leaves remained between 19.97 and 364.76 mg/kg,while that in upper com leaves decreased to 0.06 mg/kg at 21 d after application.The LC50 value of chlorantraniliprole against the neonate larvae of the laboratory susceptible population of S.frugiperda in 48 h was 0.102 mg/L,and that against the 3rd instar larvae in 72 h was 0.298 mg/L.At 21 d after application,chlorantraniliprole residues in corn leaves still exhibited high insecticidal efficacy against the F1 larvae of the field population of S.frugiperda.Spearman's rank correlation analysis indicated that the residues of the active ingredient of chlorantraniliprole in corn leaves showed extremely significantly positive correlations with the corrected mortality rates of both the neonate and 3rd instar larvae of the field population of S.frugiperda(neonate larvae:rs=0.84,P＜0.0001,n=36;3rd instar larvae:rs=0.92,P＜0.0001,n=36).The residues of the active ingredient of chlorantraniliprole in corn leaves causing 100％mortality to the neonate and 3rd instar larvae of S.frugiperda were 16.60 and 117.49 mg/kg,respectively.Field trial results showed that at 23 d after"insecticide-treated seedling transplanting"treatment with 1 650 mg/L chlorantraniliprole in spring,the proportion of damaged corn plants was 5.67％,exhibiting extremely significant difference from that of the control(32.92％),and chlorantraniliprole showed excellent control efficacy against S.frugiperda(82.95％).In autumn,however,the proportion of damaged corn plants at 23 d after application was 59.83％,and chlorantraniliprole showed the control efficacy of only 17.75％against S.frugiperda,which was lower than that in spring.[Conclusion]This study quantified the residue distribution of chlorantraniliprole in sweet corn leaves after treatment with the high-concentration chlorantraniliprole by"insecticide-treated seedling transplanting"technique.A positive correlation was observed between the residues of the active ingredient of chlorantraniliprole in corn leaves and the larval mortality of S.frugiperda.The technique demonstrated a satisfactory persistence period and effectiveness during the spring sweet corn seedling stage.