Comparative Toxicology Of Liposcelis Bostrychophila And Liposcelis Entomophila (Psocoptera, Liposcelididae)

The psocids, Liposcelis bostrychophila Badonnel and Liposcelis entomophila (Enderlein) belonging to Liposcelididae, Psocoptera, are worldwide and commonly found in various processed and unprocessed dry foods. Outbreaks of L. bostrychophila, together with L. entomophila could pose an alarming threat to stored product. Routine fumigations of warehouses and storage facilities with methyl bromide and PH₃ have failed to control these pests. In addition, the rapid development of resistance to chemical and physical treatments by the psocids has also been reported.In this study, comparative biochemistry and toxicology of L. bostrychophila and L. entomophila were investigated systematically. Through this project, the major detoxification and target enzymes relating closely to resistance to insecticide in psocids were studied, as well as other related factors, such as energy sources. Meanwhile, physiological and biochemical mechanisms of resistance by these two psocids to organophosphate and carbamate have been clarified. The results could provide necessary scientific theoretic basis for integrated management, for delaying resistance development, and for further molecular study of the two psocids. Furthermore, this study have enriched the whole study system of psocids, extended field of stored product pests. The project is supported by the Program for New Century Excellent Talents in University (NCET-04-0854) and National Natural Science Foundation of China (30570231), and lasted about 4 years, the main results are as follows:1 The toxicities of six insecticides against L. bostrychophila and L. entomophilaThe efficacies of six insecticides, cypermethrin, fenpropathrin, dichlorvos, chlorpyrifos, paraoxon, and carbosulfan, against adults of two liposcelids were determined by residual insecticide-film method. The results showed that to the contact effects of two synthetic pyrethroids, cypermeth-rine and fenpropathrin, L. bostrychophila was more susceptible than L. entomophila based on LC₅₀ values, while to carbamate, carbosulfan, L. entomophila was more sensitive; On the other hand, for organophosphorus insecticides, L. bostrychophila was only more tolerant significantly to paraoxon, while to dichlorvos and chlorpyrifos, the two psocids showed similar susceptibility. Comparing the efficacy of three kinds of insecticides, the two psocids both showed more sensitivity to synthetic pyrethroid and stronger tolerance to organophosphate.It was suggested that synthetic pyrethroid insecticide could be used as perfect grain protectant against psocid pests infesting stored products. Carbosulfan had better effectiveness against L.