| A large area of wild fruit forests are distributed in Yili valley of Tianshan Mountains in Xinjiang,and the main constructive species is Malus sieversii.It is the second-class key protected plant in China,which is the ancestor of cultivated apple and and has high scientific research value because it reveals the origin of montane broad-leaved forest,the change of flora and provide a reference for selection of cold-resistant rootstocks.Since the 1950 s,due to the interference of human activities,the area and canopy closure of the wild apple forest are both reduced,which lead the normal natural regeneration hindered.Over the past 20 years,a large number of wild apple trees died because of Agrilus mali Matsumura,Cytospora spp.,Phytophthora spp.,and other pest,which all cause further decline process of the wild apple forest ecosystem.In recent years,by means of perforating injection,aircraft spray,pruning affected branches and introducing natural enemies,the damage of A.mali has been reduced,but the situation is still severe.In this paper,the decline reasons of the wild apple forest were analyzed,and the risk assessment of the spread of A.mali in Xinjiang was assessed also.The relationship between the compound damage of A.mali and apple canker was clarified.A new disease of wild apple was studied on isolation,identification,culture and pathogenicity.The main volatile components of wild apple under different damaged states were analyzed.In order to provide technical support for wild apple forest ecological restoration and conservation,the electroantennogram and behavioral responses of A.mali to the volatiles from M.sieversii were measured and the attraction test in forest was carried out to explore the new technology of monitoring and control A.mali.The main results are as follows:1.The risk assessment of the spread of A.mali in Xinjiang was assessed by using the integrated multi-index evaluation measurement.The comprehensive risk assessment value was 2.33,which indicated that it was a highly dangerous forest pest.So the effective quarantine measures should be strengthened to prevent export of the nursery stock from the areas where the A mali occurs,meanwhile the survey,monitoring and publicity and training should be carried out.The disaster control work should be carried out in the areas effectively where A mali is distributed to prevent the spread of A mali.2.The compound harm to wild apple trees by A.mali and apple canker was studied,it was found that A.mali and apple canker usually occurred at the same parts of the wild apple tree branches,which both damaged the trees and sped up trees dead.As a result of the damage of A.mali,the growth potential of the tree was weak,which created favorable conditions for the invasion of apple canker.Regression analysis showed that the interrelationship between compound damage from A mail and apple canker and the damage of wild apple trees was a linear relation,the analysis of variance showed when both of them were introduced into regression equation as variables in turn,their effects on the regression equation were extremely significant.So measures should be made to control A.mali and apple canker damage where such compound damage occurred in wild apple forest.3.In Gongliu County and Xinyuan county wild apple forest,Phytophthora strain YLP01 and YLP04 were obtained from diseased M.sieversii tissue and rhizosphere soils using baiting techniques.Furthermore,inoculation tests were performed on stem and root segments in a greenhouse experiment to assess the pathogenicity of the P.spp.,the results showed that these two P.spp.strains pathogenicity were differently,YLP01 was pathogenic and isolates were identified using a combination of morphological and molecular tools.YLP01 is P.plurivora,a new record species which caused collar rot and made fine roots loss while YLp04 is non-pathogenic.These mentioned above,including the apple canker and A.mali,damaged the apple trees and made them declined and dieback.4.The volatiles were collected by using dynamic headspace adsorption from branches and limbs of healthy trees,damage of A.mali and damage of apple canker.There are total of 46 volatile compounds in 9 categories have been obtained,including alcohols,lipids,aldehydes,alkanes,alkenes,ketones,terpenes,ethers and others.By studying electroantennogram and behavioral responses of A.mali to the volatiles from M.sieversii trees inducd by pest and disease and the attraction test of five kinds of volatiles to A.mali in the forest.The results showed that cis-3-hexenol and decanal had strong attraction effect on the adults of A.mali behavior bioassay,which could be used in the monitoring and trapping methods of A.mali in apple forest.5.Based on study of A.mali control technology in Yili Valley of Xinjiang,the main control strategy of the wild apple forest should be ecological regulation,and should take into account the "four in one control" strategy,fully considering the relationship among pests,target tree species,beneficial organisms and living environment.Quarantine measures and pest monitoring were still important,meanwhile silvicultural measures based on pruning and fencing and biological control measures were the main measures,which helped the forest system to resist pests.In the severely damaged areas or outbreak areas,we could consider ultra-low volume aerial spray with low toxicity and low residue chemicals by aircraft to reduce the population density of A.mali.In summary,this paper analyzed the reasons of wild apple forest ecosystem decline in Xinjiang and studied main diseases and insect pests harmful characteristics of A.mali,Cytospora spp.,and Phytophthora spp.The relationship between the compound damage of A.mali and apple canker was clarified.The new technology of monitoring and control of A.mali was found.The ecological regulation of main pests was proposed to provide technical support for the implementation of ecological restoration and conservation of wild apple forest in Xinjiang. |
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