Evaluation Of Spiders Preying On Main Insect Pests In A Tea Plantation Through Comprehensive Indices

Integrated pest management(IPM)dealing with pests should reduce toxic pesticide use and it has long been one of the highlights of agricultural research.Biological control using natural enemies control pest species,and it has gained recognition as an essential component of successful IPM.Predatory natural enemies play key functional roles in biological control.However,the screening and evaluation of the main predators of insect pests has seldom been reported in the field.During the process,it is significant to identify the interactions between the pest and the potential control agent,and then screen the natural enemy species which can be effectively used to biological control.Here,we firstly employed comprehensive indices for screening and evaluating the predation of the main pests by dominant spider species in Chinese tea plantations.Through a year of intense fieldwork we found nine dominant spider species(Evarcha albaria,Phintella bifurcilinea,Coleosoma octomaculatum,Meotipa pulcherrima,Araneus ejusmodi,Neoscona mellotteei,Xysticus ephippiatus,Clubiona deletrix and Oxyopes sertatus)and two main pest species(Ectropis obliqua and Empoasca vitis)in tea canopy in study area.We established the relative dominance of the spider species and their temporal niche overlap with the pest species,and analyzed DNA from the nine spider species using targeted real-time quantitative polymerase chain reaction to identify the residual DNA of E.obliqua and E.vitis.The predation rates and predation numbers per predator were estimated by the positive rates of target fragments and the residual minimum number of E.obliqua and E.vitis in predators'guts,respectively.The results showed that only four spider species preyed on E.obliqua,and the order of potential of the spiders to control E.obliqua from greatest to smallest was N.mellotteei,X.ephippiatus,E.albaria and C.octomaculatum by the Z-score method.All tested spider species preyed on E.vitis,and the order of potential of the spiders to control E.vitis from greatest to smallest was E.albaria,N.mellotteei,A.ejusmodi,P.bifurcilinea,C.deletrix,X.ephippiatus,M.pulcherrima,O.sertatus and C.octomaculatum by the same method.The orb-weaving spider N.mellotteei and wandering spider E.albaria have the maximum potential as a biological control agent of E.obliqua and E.vitis in an IPM strategy,respectively.In this study,Z-score integrated four indices(spider species dominance,temporal-niche overlap value between spiders and pests,the positive rate of target fragment and the residual minimum number of insect pests in individual spider guts)were firstly employed to evaluate predation of predatory natural enemies on insect pests.An approach of screening and evaluating predators of insect pests through comprehensive indices was preliminarily established.