Preliminary Study On The Repellence Mechanism Of Toxin-Ⅷ From Verticillium Lecanii On Bemisia Tabaci

Bemisia tabaci (Gennadius) is a world-wide pest of cotton,vegetables,ormamentals and other agronomic crops, which has caused a serious ecomomic loss of crop production.Chemical control of Bemisia tabaci has brought a series of problems,such as resistance and residue,which doesn't conformity with the comprehensive management. Biological control is one of the most effective means of sustained management of Bemisia tabaci. The exploitation of the metabolites of entomopathogenic fungi can enrich the resource of its natural enemies . Biological activity of Verticillium lecanii toxic-Ⅷwas studied,Preliminary identified where sensilla of B. tabaci were distributed. And the ultrastructural of antennal, stylets and tarsi in B. tabaci have also been observed. These were all for exploring the possibility to control the B. tabaci. The main results are summarized as follows.(1)Biological activity of Verticillium lecanii toxic-Ⅷto B. tabaci.Insecticidal activitiews of Verticillium lecanii toxinⅧagainst 3rd instar nymph of B. tabaci were bioassayed with conventional bioassay methods.The results showed that the LC50 value was 428.76mg·L-1,and the lethallty rate was 66.33%。The repellence of Toxic-Ⅷagainst B. tabaci was studied by using selection methods of leaf covered.The results showed that Toxic-Ⅷxhibits feeding and oviposition repellence against B. tabaci, the values were 60.83% and 63.73%, respectively.(2) Preliminary identification of sensilla in B. tabaci.The feeding and oviposition repellence of Toxic-Ⅷagainst B. tabaci adults (treated with 0.3mol·L-1 hydrochloric acid on antennal,stylets and tarsi ) and B. tabaci adults not treated were compared.The results showed that the sensilla of B. tabaci are mainly distributed in antennal, stylets and tarsi.(3) Observation on the Ultrastructures of Antennal,Stylets and Tarsi in B. tabaci.The ultrastructures of antennal , stylets and tarsi of four species whiteflies (B. tabaci ,Trialeurodes vaporariorum , Aleurocybotus indicus and Aleurodicus disperse ) adults were studied with scanning electorn microscopy (SEM). The results indicated that five types of sensilla were found on the antennal, such as micortrichia, chaetae, coeloconic, campaniform and basiconic sensilla.Campaniform sensilla were not found on the antennal of Trialeurodes vaporariorum and Aleurocybotus indicus,while other sensilla were no much significant diference with B. tabaci.But there were only three types sensilla on the antennal of Aleurodicus disperse.such as microtrichia,chaetae and basiconic sensilla.what's more,the morphological structure of basiconic sensilla on the antennal of Aleurodicus disperse were very different from that on the antennal of other three types of whitefly,the number of which is more than chaetae sensilla. Two types of sensilla were found on the stylets and taris of four kinds of Bemisia tabaci.