Toxicological Mechanism Of Cornegenapsylla Sinica Yang Et Li And Safety Of Predatory Ladybirds To Different Insecticides

The studies on susceptibility of Cornegenapsylla sinica from different sites in Fujian province to insecticides were conducted.The results indicated that the Cornegenapsylla sinica in Fuzhou orchard performed more susceptible to insecticides than those in Xianyou county orchard.The different susceptibilities of C.sinica to insecticides between Fuzhou and Xianyou orchard correlated with the activities of acetylcholinesterase(AChE)and carboxylesterase(CarE),but there were not prominent correlation with the activity of glutathione-s-transferase(GSTs).In the same orchard,the different phase of C.sinica showed notable different susceptibility to a same insecticide. To a same insecticide,the susceptibility of nymph of C.sinica in the same orchard was descended as the instar increased.The discrepancy were mainly associated with the activities of ACHE,CarE,GSTs.Compared to the nymph of C.sinica,the activities of ACHE,CarE of adult performed more than that of nymph,but the activity of GSTs reversed.The toxicity and selective toxicity ratio of different insecticides to Propylaea japonica(Thunberg)and Chilomenes quadriplagiata Swartz were studied.It indicated that the LC₅₀of a same insecticide to P.japonica were more than that of C. quadriplagiata,and the selective toxicity ratio also did.Analysis on the toxicity and selective toxicity ratio of different insecticides to predatory ladybirds.The results showed that the imidacloprid,thiamethoxam and fipronil performed lower toxicity but higher selective toxicity ratio to predatory ladybirds,the insecticides of avermectin and alphacypermethrin taked the second place,but cyhalothrin,deltamethrin,fenvalerate, fenpropathrin and chlorpyrifos performed the higher toxicity but lower selective toxicity ratio.The chlorpyrifos performed the lowest selective toxicity ratio among all the experiment insecticides.Furthermore,the selective toxicity ratio of a same insecticide to 1-2^ndinstar nymph of C.sinica and predatory ladybirds were higher than that of 3-4^th instar nymph and adult did.The toxicity test of insecticides to C.sinica and predatory ladybirds could instruct the pests control in Longan orchards. The functional response of P.japonica and C.quadriplagiata to C.sinica conformed to the model of Hollingâ…¡.In the same prey density of the same instar nymph or adult, the larger of predatory quantity,higher sudden attacking rate and lower handle time of C.quadriplagiata compared to the P.japonica were observed.Except on the prey density of 10 and 20 pests per bottle of adult of C.sinica,there were significant discrepancy(p<0.01)of predatory quantity between P.japonica and C.quadriplagiata. The predatory quantity sequence of ladybirds to different development phase of C.sinica were 1-2^ndinstar nymph,3-4^thinstar nymph and adult,respectively.Sublethal doses of insecticides could reduce the predatory quantity of ladybirds to C. sinica.The studies revealed that the functional response of ladybirds which pretreated with sublethal doses of insecticides were still conformed to the model of Hollingâ…¡,just only the parameters of model had atlered,the alteration showed that sudden attacking rate "a",handle time "T_h" and the searching efficiencies "S" were reduced.But different insecticides performed different effects on the fuctional response.Except fipronil,a same insecticide performed more severe effects on C.quadriplagiata than P.japonica.Integrated analysis on the effects of different insecticides on the predatory ladybirds from aspect of toxicity,selective toxicity ratio and the sublethal doses effected on the functional response.It showed that the insecticides of imidacloprid,thiamethoxam, fipronil,avermectinhad and alphacypermethrin performed more safety and less adverse effects on P.japonica and C.quadriplagiata,but the insecticides of cyhalothrin, deltamethrin,fenvalerate,fenpropathrin and chlorpyrifos performed the less safety and more severe adverse effects on the two kinds of predatory ladybirds.