Effects Of Myzus Persicae Density On Parasitism Of Aphidius Gifuensis

In the process of vegetable production,Myzus persicae is one of the most im portant vegetable pests.Not only its own serious harm,but also the sp read of a variety of viral diseases,resulting in serious loss in production,and seriously reducing product quality.At present the main method to control aphid is us ing chemical pesticides.By doing this,it not only increases the cost of production,but also causes serious pesticide residue and environmental pollution.Therefor e,it is ur gent to strengthe n the research on biological control of aphid pests,and to use ef fective natural enemy insects to prevent and control M.persicae.And A.gifuensis as dominant aphid parasitoids,has been widely used in biological control in M.persicae.To evaluate the poten tial effect of A.gifuensis in M.persicae in biological control,this research studied the effect of the size of the space,the host density and A.gifuensis own density's influence in its contro l efficiency.We also com bination the res ults with mathematical model in order to understand the prevention and control effect of A.gifuensis to the aphid,M.persicae.In this research,we hope to provide a theoretical basis for the effective release of A.gifuensis in field.The main contents and results of this study are as follows:1.Functional response of A.gifuensis to M.persicae was studied in petri dish and barrel respectively and in 5 dif ferent M.persicae densities.Then we calculate p arasitic rate and fit functional responses equation.(1)In barrels,the functional responses of A.gifuensis were Holling II type: functional responses equation is Na=0.9043No/(1+0.01 15No),instantaneous attack rate(a)is 0.9043,processing time(Th)is 0.0115,the daily maximum number of parasiting M.persicae is 78.9.(2)In petri disc,the functional responses of A.gifuensis were Holling II type:functional response equation is Na=0.9310No/(1+0.01 18No),the instantaneous attack rate(a)0.9310,processing time(Th)is 0.0118,the daily maximum number of parasiting M.persicae is 108.9.(3)In 5 different M.persicae densities,parasitic rates in barre l were respectively 74.17%,53.60%,46.57%,32.83%,25.14% in petr i dishes were 77.14%,57.60%,50.33%,39.22%,and 26.64%,respectively.There was no significant dif ference between the two treatments.Through this first test,we can presume that the optimum A.gifuensis to M.persicae ratio may be 1:50,which means that when 1 A.gifuensis parasite 50 M.persicae the control effect are most effective.Then this resu lt provides the theory basis f or the setting of A.gifuensis release--the next step of the research to evaluate the conttol effect of A.gifuensis in different pairs of A.gifuensis.2.In 100,300 and 500 aphid densities,each aphid density were released 3 pairs,5 pairs,7 pairs and 10 pairs of A.gifuensis.Then compare the calculated parasitic rate and then fit interference reaction equation.(1)In 100 aphid dens ities,the parasitic rate on the rele ase of 7 A.gifuensis was significantly lower than the release of 5 pairs of A.gifuensis parasitic rate.It indicate that it is not the more the better in releasing A.gifuensis.To achieve the expected optim um control effect,we use m ore pairs of A.gifuensis than expect,so it also ind icate that the intera ction between A.gifuensis reduces parasitism rate of A.gifuensis.(2)In 300 and 500 aphid dens ity,with the increase of the quantity of parasitoids,the parasitism rate gradu ally increased,but the parasitic rate of single A.gifuensis decreased,parasitism rate(E)dec reased.The results showed that th e parasitism of A.gifuensis is decreased by its density and between A.gifuensis there has obvious interference effect.(3)The relationship b etween parasitism efficiency and A.gifuensis density can be fitted in the E=0.3577P^-1.1723 model,E=0.0658P^-0.5392 model and E=0.03888P^-0.4963 modelAbove all,the problem of the interference effect between A.gifuensis should be considered in order to determ ine the appropriate number of release.On the other hand,the conclusion that releasing 5 couples of A.gifuensis can have the best parasitiaed ef fect under the space o f 10 dm3 and 100 M.persicae density in this experiment can be used as the theoretical basis for the release of A.gifuensis in field in the given space size and Myzus persicae density.