Study On The Control Effect Of Hippodamia Variegata(Goeze) On Bemisia Tabaci(Gennadius) And Aphids In Greenhouse

The harm of aphids and Bemisia tabaci has caused great losses to the production of protected vegetables.Hippodamia variegata(Goeze)as the dominant natural enemy population in Xinjiang.which has good control effect on aphids and B.tabaci,and has high research value.In this study,we determined the predation and preference of H.variegata(Goeze)to three kinds of aphids and B.tabaci by laboratory predation experiments.By using cage experiment in greenhouse,the Natural Enemy/Pest ratios for controlling three aphids and B.tabaci was determined by setting different Natural Enemy/Pest ratios.Artificial simulation of three control methods to determine the release of different ways of H.variegata control of aphids,and thus provide a scientific basis for the use of H.variegata biological control facilities vegetable aphids and B.tabaci.The main contents and research results are as follows :(1)Through the indoor predation experiments,it was determined of H.variegata had a certain control effect on three kinds of aphids and B.tabaci.The maximum predation of H.variegata on M.persicae(Sulzer)was female adults > fourth instar larvae > third instar larvae > male adults > second instar larvae > first instar larvae,The maximum predation of H.variegata on A.gossypii Glover and A.craccivora(Koch)were female adults > male adults >fourth instar larvae > third instar larvae > second instar larvae > first instar larvae,The maximum predation of H.variegata on B.tabaci was lower than others,the maximum predation of female adults was 110/day,of fourth instar larvae was 39/day.With the increase of prey density,the predation of aphids and B.tabaci increased,which was consistent with Holling-II equation.The finding effect of H.variegata on three aphids and B.tabaci decreased with increasing prey density,and the average predation rate tended to decrease with increasing their own density,in line with the Hasse-II model.H.variegata showed predation preference to A.gossypii Glover.(2)By experiment of setting cage in greenhouse,The control effect on A.craccivora(Koch)was more than 90% in the short term after releasing adults of H.variegata at the ratio of 1:10 and 1:20;but the colonization rate of H.variegata is low and the cost is high in the later stage of control.When the ratio was 1:60 and 1:80,the late control effect was low and the duration was short.Sustainable control of A.craccivora(Koch)at the ratio of 1:40.Release H.variegata to control M.persicae(Sulzer),When the ratio was 1:20 and 1:40,the control effect is better,but the cost is higher than other ratios.When the ratios was 1:80 and1:100,the control effect was poor at 35 d,which was 46.6% and 26.6% respectively.Sustainable control of M.persicae(Sulzer)at the ratio of 1:60.When releasing H.variegata to control A.gossypii Glover,the control effects of ratios of 1:10,1:20 and 1:40 were higher than those of ratios of 1:60 and 1:80 treatment groups after 7～35 d of release,and better control effects were achieved.Considering the release cost,it is recommended to use 1:40 as a reference ratio for controlling A.gossypii Glover.When controlling B.tabaci,the control effect of 1:5 was higher than other treatment groups,showing a certain control effect.(3)By simulating field applications in the greenhouse.Three three release methods were set up.It was determined that the control effects of different release methods were significantly different from those of the untreated group,achieved the purpose of pest control in a short time.