Study On The Adaptability Of Dastarcus Helophoroides Artificially Bred To Monochamus Alternatus

As an effective biological control method,Dastarcus helophoroides(Fairmaire)(Coleoptera: Bothrideridae)is one of the important parastic natural enemies of Monochamus alternatus(Coleoptera: Cerambycidae),an import forest pest in China.It can parasitize larvae more than 3rd instar,pupae and newly emerged adults.Obtaining a large number of populations through artificial breeding is the prerequisite and basis for achieving biological control of pests.At present,most of the D.helophoroides are artificially bred using alternative hosts,and it is unclear whether the population will affect the parasitic adaptability to natural host M.alternatus after successive generations of breeding.In this paper,by measuring the changes in parasitic ability of three consecutive generations of D.helophoroides,the change in the ability to search for hosts,and the changes in physiological and biochemical indexes before and after the host was parasitic,the adaptability of D.helophoroides to natural host M.alternatus after artificial breeding.The results of this study provide a theoretical basis for clarifying the rejuvenation cycle of artificially bred D.helophoroides population,and have important guiding significance for optimizing the scientific breeding and release technology of D.helophoroides.The results are as follows:The parasitic ability of the artificially bred multi-generation D.helophoreides parasitizing M.alternatus showed that the parasitic effect was degraded as the number of generations increased.This phenomenon was more likely to occur at higher inoculation densities.Increasing the number of generations will reduce the mortality rate of M.alternatus.Increasing the number of inoculations with D.helophoroides can significantly reduce the mortality of M.alternatus caused by the increase in the number of generations.Increasing the number of generations significantly reduced the parasitic rate of D.helophoroides,increased the inoculation density,the parental parasitic rate increased significantly,and the offspring parasitic rate fluctuated.Increasing the number of generations significantly reduced the survival rate of the D.helophoroides larvae and increased the inoculation density.The change trend was similar to the parasitic rate.As the number of generations increased,the larval and cocoon phases increased.Increasing the inoculation density significantly reduced the developmental period of each generation.As the number of generations increased,the cocooning rate decreased significantly;the cocooning rate of each generation increased significantly with increasing inoculation density.As the number of generations increases,the feathering rate of D.helophoroides will not be affected,but the proportion of females will decrease significantly.After being parasitized by multi-generation D.helophoreides,Physiological and biochemical measurements in the hemolymph of M.alternatus showed that the trehalose and total sugar content in the host hemolymph was increased after parasites of different generations D.helophoreides.Over time,the hosts of the first and second filial generations of parasites successfully showed lower trehalose content,and the trehalose and total sugar contents of the host's hemolymph after parasitization were more stable with time.After the parental generation successfully parasitic,the reducing sugar in the host hemolymph is lower than the non-parasitic at first,and it gradually increases to exceed the non-parasitic.After the parental generation successfully parasitized,the specific activity of phenoloxidase in host hemolymph was inhibited,and the inhibition was greater than that of the first and second filial generations.Parental filial generation regulation of host nutritional metabolism and immune enzymes is more stable.Y-tube test showed that after multiple generations of artificial breeding using alternative hosts,the adult emerged after inoculating the natural host,when faced with the natural host and the alternative host,the first filial generation began to show a preference for the alternative host,and this preference gradually increased with the increase of generations,as the selection ability of the second filial generation began to show a significant difference compared with the parental generation.However,this preference did not appear in the selection of alternative hosts and air,and there was no significant difference in the selection of natural hosts and air.In summary,as the number of generations increases,the adaptability of artificially bred populations to natural hosts declines to a certain extent in terms of parasitism,host physiological and biochemical regulation,and host search capabilities.The gradually increasing of adaptability as the number of generations increases,it may mainfest in more indicators are affected,or it may mainfest in the continuous decline of individual indicators.Therefore,measures such as population domestication and rejuvenation adjustment are required to ensure the good development of the population of D.helophoroides and the high control effect on M.alternatus larvae.