Interspecific Interactions Between Serangium Japanicum And Encarsia Formosa And Their Control Efficiency On Bemisia Tabaci

Bemisia tabaciis one of the most important pests in agricultural production worldwide.It is highly polyphagous,attacking more than 600 plant species(including vegetables,horticulture and crop plants).Because of their high reproductive rate,multiple generations per year and ability to rapidly develop resistance to insecticides,biological control becomes the primary method to suppress whitefly populations in agroecosystem s.Encarsia formosa has been widely used in the control of the whitefly pests and has been commercialized.Serangium japanicum is one of dom inant predators of Bemisia tabaci.Todate,there are few reports on using two dif ferent natural enemies to con trol Bemisia tabaci.Therefore,the functional response,foraging behavior and control ef ficiency of two kinds of natural enem ies were studied under laboratory condition.The main results were as follows:1.The functional responses of S.japonicum and E.formosa predating on/parasitizing the third instar nymph of B.tabaci fitted the m odel of Holling II type well.W hen S.japonicum and E.formosa coexisted,the fitted Holling disc equation of the ladybird was Na=0.9553N/(1+0.0043N).The handling time decreased and instantaneous attack rate increased compared to independent S.japonicum.When S.japonicum and E.formosa coexisted,th e Holling equation of E.formosa was Na= 0.1014N/(1+0.0140N)(hos t feeding)and Na= 0.0659N/(1+0.0028N)(parasitizing).The handling time increased and instantaneous attack rate reduced compared to independent E.formosa.2.Host-handling behavior of the ladybird mainly included feeding,crawling,cleaning,resting,vibrating wings and excreting when S.japonicum and E.formosa coexisted.The feeding time,resting time and handling tim e decreased,but the crawling tim e and searching rate increased com pared to independent S.japonicum.Host-handling behavior of the parasitoid mainly included oviposition ing,searching,feeding,walking,preening,probing,piercing,resting,feeding honeydew.The feeding time,searching rate and host-handling tim e decreased,but oviposition time increased compared to independent E.formosa.3.The order of predation preference of S.japonicum adult against B.tabaci wasfourth instar nymph >third instar nym ph > egg;the pr eference order forfourth instar larva of the ladybirdwasthird instar nym ph > fourth instar nym ph > egg.S.japonicumadult and larva preyed on parasitized whitefly nymphs,but prefered unparasitized whitefly nymph to parasitized nymph.4.Two S.japonicum per plant and fourladybirds per plant can control B.tabaci population development,and four S.japonicum per plant m ade a better control efficiency.The control efficiency of two ladybirds per plant on B.tabaci adults and nymphs were 52.6%-82.7% and 89.9%-96.7%,respectively;the control efficiency of four ladybirds per plant were 78.2%-93.2% and 92.0%-98.2%,re spectively.The control ef ficiency of E.formosa against the w hitefly adults and ny mphs were 59.4%-75.9% and 63%-80.4%,respectively.