Toxiciies And Screening Synergies Of Nine Insecticides Against Aphis Gossypii Glover

Aphis gossypii Glover?Hemiptera:Aphididae?is one of the important pests in the melon vegetables production,which widely distributes all over the world.The adults and nymphs feed the juice of leaves back and growing points of host plants,leading to curl,yellowing and even abscission of the leaves.Aphids also secret honey dew when feeding,which causes sooty mold on leaves,meanwhile,they serve as a vehicle for viral transmission to the plants.Aphids has been one of the important prevention and control targets in the melon vegetables production due to its short generations,large reproduction,evolving resistance to insecticides rapidly,adverse influences on the yield and quality of melon vegetables such as cucumbers.In order to effectively control melon aphids,reduce chemical consumption,delay the aphid resistance,and improve the pertinence,effectiveness and scientific nature of chemical insecticides against aphids,the research determined the sensitivity of melon aphids to nine common insecticides,selected the synergistic mixtures of two insecticides under greenhouse condition and evaluated four kinds of mixturess selected under fields condition,hoping to provide theoretical basis for melon prevention and control.The main results are as follows:1.Sensitivity of melon aphids to nine insecticidesThe sensitivity of melon aphids collected from Tai'an,China to the nine commonly used insecticides was determined by the leaf-dipping method.The results showed that sulfoxaflor and flupyradifurone had the higher toxicities at 24h and 48h with 48h-LC₅₀ of 2.35 mg/L for sulfoxaflor and 5.42 mg/L for flupyradifurone,respectively.The pymetrozine and lambda-cyhalothrin had the relatively lower toxicities with 48h-LC₅₀ values of 86.33 mg/L for pymetrozine and 117.57 mg/L for lambda-cyhalothrin,respectively.2.Screening of synergistic mixturesOn the basis of different mass ratios,the following mixtures were designed:flupyradifurone and pymetrozine,sulfoxaflor and pymetrozine,flupyradifurone and lambda-cyhalothrin,sulfoxaflor and lambda-cyhalothrin,spirotetramat and dinotefuran,and spirotetrama and cyantraniliprole.The toxicities of these mixtures to melon aphids was determined and the significant synergism was observed in the mixtures of flupyradifurone and pymetrozine 1?5,sulfoxaflor and pymetrozine 1?3,flupyradifurone and lambda-cyhalothrin 1?5,sulfoxaflor and lambda-cyhalothrin 1?5,spirotetramat and dinotefuran 8?1,spirotetramat and cyantraniliprole 10?1,spirotetramat and flupyradifurone8?1,and spirotetramat and sulfoxaflor 10?1.3.Field testThe field experiment included pymetrozine,lambda-cyhalothrin,flupyradifurone,sulfoxaflor,and four mixtures with synergism in greenhouse experiment.Flupyradifurone?22.5 and 38.25 g a.i./hm²?showed quick-acting and long-last toxicity against melon aphids with good control efficacy greater than 80%at day 1 and greater than 90%on day 7,respectively.Sulfoxaflor?7.5²2.5 g a.i./hm²?also provided quick-acting and long-last toxicity with efficacy 70⁹9.72%on days 1 and 7.Pymetrozine showed good long-last toxicity while performed poorly in quick-acting toxicity with efficacy 30%on day 1 and 90%on day 7,respectively.Lambda-cyhalothrin showed poor quick-acting and average long-last toxicity with efficacy 60%on day 1,whereas the control efficacy decreased on day 14.Concerning mixtures with synergism,the mixture of flupyradifurone and lambda-cyhalothrin?mass ratio,1?5;6.25 g a.i./hm²?,sulfoxaflor and pymetrozine?mass ratio,1?3;67.5 g a.i./hm²?showed 84%efficacy on day 1,and the control efficacy increased rapidly on days 3,7 and 14 and retained above 95%,which can provide a long-term control of melon aphids.From the point of view of economic and control efficacy,the mixture of flupyradifurone and lambda-cyhalothrin?mass ratio,1?5?,sulfoxaflor and pymetrozine?mass ratio,1?3?was recommended for the control of melon aphids.