| Spodoptera frugiperda（Smith）,the fall armyworm（FAW）,a major migratory agricultural pest,is native to tropical and subtropical areas of North America.FAW has the characteristics of wide host range,strong migratory ability,strong reproductive ability,strong insecticide resistance and adaptability.Due to the characteristics of strong insecticide resistance and concealment of early damage,the management of FAW urgently needs precise control strategies.Therefore,we did the following three research experiments.The results are as follows:（1）Control efficacy of six seed-coatings against FAWIn this study,the control effects of chlorantraniliprole（CHL）,cyantraniliprole（CYA）,chlorantraniliprole·clothianidin（CHL+CLO）,cyantraniliprole·thiamethoxam（CYA+THI）,clothianidin（CHL）and thiamethoxam（THI）against FAW larvae by treating corn seed were tested both in laboratory and field conditions.Laboratory experiments showed that FAW mortality in the CHL+CLO and CYA+THI treatments exceeded 84.00%at 14 days after seedling emergence（DAE）;this mortality was similar to seed treated with CHL or CYA treatment alone,but was much higher than CLO or THI treatment.Two independent field experiments showed that CHL+CLO and CYA+THI treatments resulted in 79.84%-87.88%mortality at 7 DAE and68.93%-77.94%at 14 DAE,respectively,suggesting that these insecticidal combinations effectively control FAW.Lastly,The control cost of CHL+CLO is270.68￥per hectare,which reduced 270.68￥when compared to CHL（541.36￥?ha-1）.Smilarly,control cost of CYA+THI is 288.70￥per hectare,which reduced 72.19￥per hectare when compared to CYA（360.89￥?ha-1）.CHL+CLO and CYA+THI can effectively control FAW larvae on corn seedlings up to 14 DAE.The application of CHL+CLO and CYA+THI as seed treatments would reduce the cost of FAW control since the dosage of CHL and CYA in the combined treatment is lower than the dose used in individual applications.（2）Effects of six seed-coatings on safty evaluation and stress-related physiological indexes in corn plantsBy investigating the emergence rate,agronomic characters and residues in maize leaves of six kinds of seed-coatings（CHL,CYA,CHL+CLO,CYA+THI,CHL,THI）,the CHL+CLO and CYA+THI treatments showed no negative effects on the growth and development of corn seedlings.Furthermore,insecticidal residues of CHL+CLO and CYA+THI in corn were lower at 28 DAE in compared to residues in single application.The physiological indexes of corn seedlings treated with six seed-coatings at 3,7,14,21 and 28 DAE were measured by double antibody one-step sandwich enzyme-linked immunosorbent assay（ELISA）.The results showed that peroxidase（POD）activity was not altered in corn seedlings treated by THI and CLO at 7 DAE,and other emergence times were significantly higher than those of the control.POD activity was significantly improved in corn seedling treated with CHL,CYA,CHL+CLO and CYA+THI treatments at 3-28 DAE.Total phenol content of corn seedlings was not altered by THI at all sampling dates,but was significantly improved by CHL,CYA,CHL+CLO,CYA+THI and CLO treatments.However,catalase（CAT）and superoxide dismutase（SOD）activity of corn plants treated with CHL,CYA,CHL+CLO,CYA+THI and CLO were obviously decreased at each smapling date,except for THI.Furthermore,no significant difference was detected in glucose-6-phosphate dehydrogenase（G-6-PDH）activity of corn seedlings among these six insecticide treatments at each sampling date.In summary,six seed-coatings are safe for the growth and development of maize seedlings.CHL,CYA,CHL+CLO,CYA+THI and CLO treatments improved the POD activity and total phenol content of corn seedlings during 3-28 DAE,but decreased CAT and SOD activities of corn seedlings.The seed-coatings had no effect on G-6-PDH activity of corn seedlings.Thus,except THI,other insecticides promoted the growth of maize plants by improving the stress resistance of maize plants.（3）Toxicity and control efficacy of seven bio-insecticides against FAWToxicity and control efficacy of seven bio-insecticides（spinosad,Mb NPV,Empedobacter brevis,Metarhizium anisopliae,Bt-1,Bt-2,Bt-3）against the 2nd instar larvae of FAW both in laboratory and in field were evaluated.The results of laboratory bio-assay showed that spinosad had the greatest toxicity to FAW,the LC50was 0.0080μg/m L,and the next highest was the Mb NPV（8.75×104PIB/m L）,the virulence of Mb NPV to FAW was 1.10×106cfu/m L,while the virulence of E.brevis was 4.63×107cfu/m L.The results of field experiments showed that the application of spinosad,Mb NPV,Bt-1 and Bt-3 had the best control effects on FAW,all of which were more than 85%at 3 d after treated.The control effects of E.brevis and Bt-2 on FAW,were more than 75%,which were significantly higher than that of M.anisopliae;The control effects of spinosad,Mb NPV and Bt-1 on FAW,were more than 88%,and the control effects of E.brevis,Bt-2 and Bt-3 on FAW were 62.01%-79.20%on 7DAE treated.In consequence,spinosad,Mb NPV and Bt-1 should be applied to control these pests in case of urgent needed,while E.brevis,Bt-2 and Bt-3 are suitable for preventive control and for the purpose of resistance control. |
