Study On The Effect Of Preying On Main Stored Grain Pests By Xylocoris Flavipes (Reuter) And Withius Piger (Simon)

Studying predation of predators in grain storage has the important significance on developing a new biological control method,reducing chemical pollution and decreasing pest resistance to pesticides.Two kinds of predators’dominant grain species were confirmed.Predation abilities of Xylocoris flavipes and Withius piger for 11 grain pests and predation capacity of X.flavipes and W.piger on 9 grain pests were studied.These grain pests included Tribolium Castanea,Tribolium confusum,Liposcelis entomophila,Liposcelis bostrychophila,Cryptolestes ferrugineus,and Lasioderma serricorne.Function reaction of W.piger to catch and feed on L.bostrychophila and predation function reaction and parameters of X.flavipes for L.bostrychophila,T.castaneum,O.surinamensis and C.ferrugineus were discussed.Finally,control ability of X.flavipes on grain pests under the simulation warehouse and actual warehouse was studied.The main results were stated as follows:1.The predators in the forth grain ecological zone to the seventh grain ecological zone were investigated.The research results showed that X.flavipes and W.piger belonged to dominant species for predators’grain pests.Under the laboratory conditions,predation abilities of X.flavipes was measured.The results showed that X.flavipes might capture larva(nymph)and eggs of 11 grain pests,including T.castaneum,O.surinamensis,C.ferrugineus,L.serricorne,L.entomophila,and L.bostrychophila.W.piger only could capture larva(nymph)of above-mentioned 11 grain pests,but couldn’t capture eggs.2.The process that W.piger captured T.castaneum was divided into five processes:seeking,capture(prey),paralysis,juice and rest.The W.piger indicated that maximum predation in third-stage larva of T.castaneum was 19.0 heats/day,and minimum predation in third-stage larva of L.serricorne was 1.2 pest/day;W.piger’s predation functional response in third instar L.bostrychophila indicated that within the density range of 10-160 pests,L.bostrychophila belonged to the HollingⅡmodel.In theory,the maximum predation was78.8 pests,while the discovery domain was 0.03m~2.3.The control ability of female adult X.flavipes in third instar larva(nymph)of T.castaneum,C.ferrugineus,O.surinamensis and L.bostrychophila was studied.It could be found that X.flavipes could capture 9 grain pests.By contrast,X.flavipes reached the maximum predation for T.castaneum(18.8 pest/day).In laboratory conditions,the X.flavipes’predation functional response equation in several grain pests’third instar larva,their searching effect,intraspecific interference reaction and predation preference for different preys were studied.The findings indicated that female adult X.flavipes’predation function reaction equation for larva(nymph)of T.castaneum,C.ferruginous,O.surinamensis and L.bostrychophila confirrmed to HollingⅡequation.According to the equation,it could be found that X.flavipes had the maximum daily predation in third instar L.bostrychophila(44.6pest/day).The searching effect of X.flavipes for various pests were reduced with the increase of prey density.After prey density reached certain quantity,the average predation rate of preys was reduced with the increase of X.flavipes.By making a comparison on preference selection system Cain index of X.flavipes for different pests,it turned out that X.flavipes preferred to capture third instar larva of O.surinamensis and C.ferrugineus.4.Some X.flavipes was respectively put in the simulation warehouse at 28±1℃and50±10%and in an actual warehouse.The findings showed that after putting different X.flavipes in simulation warehouse,it reached more than 70%of control effect for pests three months later.Beneficial and injurious ratio didn’t have the significant influences on grain pests.Control effect of X.flavipes for 4 pests included O.surinamensis>L.bostrychophila>C.ferrugineus>T.castaneum.X.flavipes was placed in the actual warehouse of the fifth grain ecological zone and the seventh grain ecological zone.After the ninety-eighth days,it turned out that the pests’death rate was 56.3%at Shaoguan depot and that of Changsha depot was56.7%.Therefore,X.flavipes can be used as natural enemies of storage pests and has research and application prospects.