Determination Of Toxicity Of Insecticides To Main Pests In Cotton Field And Safety Evaluation Of Hippodamia Variegata(Goeze)

The toxicity of insecticides to main pests in cotton field and safety evaluation to Hippodamia variegata?Goeze?was assessed by using spray tower method,respectively.At the same time,the sublethal concentration(LC₂₀)and median lethal concentration(LC₅₀)of neonicotinoid insecticide cycloxaprid against adult H.variegata were also determined.Then,the sublethal effect of cycloxaprid on adult H.variegata was evaluated through the changes of the parameters of adult survival rate,lifespan,pre-oviposition period,fecundity and egg hatching rate of ladybugs,whichtreated with two concentrations of cycloxaprid.The main results are as follows:1.Toxicity test of 10 Insecticides to Aphis gossypii?Glover?and Safety Evaluation to H.variegata.The insecticide with the highest relative toxicity index to A.gossypii was sulfoxaflor?35.11?,the lowest was pymetrozine?1.00?.According to the order of safety index from highest to lowest,sulfoxaflor>acetamiprid>imidacloprid>cycloxaprid>thiamethoxam>carbosulfan>nitenpyram>dinotefuran>spirotetramat>pymetrozine.The highest safety index of insecticides against adults of H.variegata is spirotetramat?7.06?,the lowest was nitenpyram?1.02?.According to the order of safety index from highest to lowest,spirotetramat>carbosulfan>sulfoxaflor>pymetrozine>imidacloprid>dinotefuran>thiamethoxam>cycloxaprid>acetamiprid>nitenpyram.The highest safety index of insecticides against 3rd instar larvae of H.variegata was sulfoxaflor?2.37?,the lowest was dinotefuran?0.59?.According to the order of safety index from highest to lowest,sulfoxaflor>spirotetramat>imidacloprid>thiamethoxam>pymetrozine>acetamiprid>cycloxaprid>nitenpyram>carbosulfan>dinotefuran.2.Toxicity test of 5 Insecticides to Tetranychus truncatus?Ehara?and Safety Evaluation to H.variegata.The insecticide with the highest relative toxicity index to T.truncatus was abamectin?310.93?,the lowest was propargite?1.00?.According to the order of safety index from highest to lowest,abamectin>pyridaben>clofentezine>hexythiazox>propargite.The highest safety index of insecticides against adult adults of H.variegata was clofentezine?13.84?,the lowest was propargite?1.26?.According to the order of safety index from highest to lowest,clofentezine>hexythiazox>abamectin>propargite>pyridaben.The highest safety index of insecticides against3rd instar larvae of H.variegata was clofentezine?7.34?,the lowest was pyridaben?1.19?.According to the order of safety index from highest to lowest,clofentezine>abamectin>hexythiazox>propargite>pyridaben.3.Determination of Toxicity of 6 Insecticides to Helicoverpa armigera?Hübner?and Evaluation of the Safety of H.variegata.The insecticide with the highest relative toxicity index to H.armigera was emamectin benzoate?69.39?,the lowest was beta-cypermethrin?1.00?.According to the order of safety index from highest to lowest,emamectin benzoate>chlorantraniliprole>indoxacarb>methomyl>chlorpyrifos.The highest safety index of insecticides against adult adults of H.variegata was emamectin benzoate?40.62?,the lowest was chlorpyrifos?0.88?.According to the order of safety index from highest to lowest,emamectin benzoate>chlorantraniliprole>beta-cypermethrin>indoxacarb>methomyl>chlorpyrifos.The highest safety index of insecticides against 3rd instar larvae of H.variegata was emamectin benzoate?23.75?,the lowest was chlorpyrifos?0.61?.According to the order of safety index from highest to lowest,emamectin benzoate>chlorantraniliprole>beta-cypermethrin>methomyl>indoxacarb>chlorpyrifos.4.Effects of cycloxaprid on the lifespan and fertility of adult H.variegata.Cycloxaprid at a certain concentration had inhibition effects on the survival rate,lifespan,pre-oviposition period,fecundity and egg hatching rate of adult H.variegata in varying degrees.The longest lifespan of females treated with high-concentration cycloxaprid was proved 15 days shorter than that of control treatment.Also,the adult survival rate decreased rapidly in a certain period due to the high concentration of cycloxaprid.Both the high and low concentrations of cycloxaprid significantly shortened the lifespan and prolonged the pre-oviposition period of adults.Cycloxaprid in low and high concentration both caused the instable daily egg production of H.variegata while significantly decrease of eggs arise in high concentration only.The egg hatching rates of treatment group in various concentrations were lower than that in the control groups.In summary,some insecticides with better security and selectivity are not only highly toxic to major pests in cotton fields but also less toxic to their natural enemy insects,such as sulfoxaflor commonly used to control A.gossypii,avermectin commonly used to control T.truncatus,emamectin benzoate commonly used to control H.armigera.The new insecticide cycloxaprid has a certain inhibitory effect on the survival and reproductive ability of ladybug at low concentration.The research results provide a scientific basis for the rational use of chemical pesticides in the field and the protection of natural enemies.