Occurrence And Host Selection Mechanism Of Trypophloeus Klimeschi Eggers

Trypophloeus klimeschi Eggers(Coleoptera,Curculionidae,Scolytinae)is a new recorded species in China that can be devastating to stands of Populus alba var.pyramidalis Bunge.T.klimeschi is native to the Kyrgyz Republic.After an outbreak in 2003 in Xinjiang Province,T.klimeschi spread rapidly to adjacent areas and is now found in Dunhuang,which posing a huge threat to the construction of plantations in the northwest of China.As a new invasive species,no effective natural enemies have yet been discovered,and T.klimeschi hides in the interior of the bark of P.alba var.pyramidalis.Traditional physical and chemical control cannot effectively control the occurrence of T.klimeschi,and easy to cause pollution of the ecological environment.Study on the biology,occurrence regularity and composition of intestinal microbial community of T.klimeschi,which not only plays an important role in revealing the outbreak internal mechanism of T.klimeschi,but also owns great scientific value and practical meanings for indoor and outdoor detection of host volatile constituents and biological activity,host selection mechanism,pheromone development and governance of T.klimeschi.The main objectives of this study are the morphological characteristics,biological characteristics and occurrence of the T.klimeschi;the characteristics of adult antennal receptors;the identification of host and non-host volatile components;indoor behavioral and field trapping techniques;and the interaction between the intestinal microorganism and T.klimeschi.The aim is to explore the law of the occurrence of the T.klimeschi,the chemical information material composition and application technology.The research has achieved the following results:1.The morphological characteristics,adult susceptor characteristics,receptor type,receptor distribution characteristics and regularity of T.klimeschi were obtained.There were differences in male and female morphology.There were three sharp-angled bulges between the fifth and sixth rows of tumor-like bulges near the tail of the male coleoptera,while the females are regular shapes.There were not obvious difference of antennal sensilla between male and female.Five types of sensilla identified on the antennas of both female and male were sensilla trichodea,zigzag sensilla,bud-shaped sensilla,sensilla basiconica and hammer sensilla.Among all parts of antennae,majority of sensilla spreaded on the club of the antennae,and the sensilla were densely encircled.Sensilla triehodea were the dominant type.The distributions of sensilla types were clear.Sensilla trichodea and bud-shaped sensilla distributed on club of the antennae only;zigzag sensilla only distributed on funicle and flagellum;sensilla basiconica only distributed on the end of funicle;hammer sensilla distributed on the first joint of flagellum.2.There were two generations of T.klimeschi per year and the pest overwintered in the form of mature larvae.There were two peak periods in a year.Mature larvae began to pupate in early May.Adults started to emerge from mid-May with a peak from late-May till mid-June.Second generation larvae pupated in mid-July.The peak of adult emergence was in August.T.klimeschi had strong species-specificity to P.alba var.pyramidalis especially at 10-20 cm DBH(the diameter measured at breast height).The damaging situation in the canopy closure forests of 0.5-0.69 was lowest.These results had important guiding significance for the construction and renovation of the Dunhuang shelterbelt.At the same time,two kinds of artificial diets of T.klimeschi were successfully developed.The two kinds of artificial diets can meet the nutritional requirements of normal growth of the T.klimeschi.Under indoor breeding conditions,the T.klimeschi were in a neat state,the pupation rate and the eclosion rate are high,and the larval mortality rate was kept at a low level.In addition,compared with the natural conditions in the field,the duration of development by feeding two artificial diets were reduced by more than double.This study established the source of T.klimeschi for related population dynamics,molecular biology and other related research.3.We comprehensively investigated the biodiversity and activity of bacterial and fungal communities in the different developmental stages of T.klimeschi and the difference between sexes and two generations.Proteobacteria,Actinobacteria,Firmicutes and Bacteroidetes dominate in the guts of T.klimeschi.Halomonadaceae,Xanthomonadaceae,Ochrobactrum,Pseudomonas,Phyllobacteriaceae,Dietziaceae,Microbacterium and Sphingobacterium were most prevalent in the larvae.Pseudomonas,Dietziaceae,Microbacterium,and Herbiconiux were significantly increased in overwintering mature larvae.Adults harbored high proportions of Erwinia,Acinetobacter,Corynebacterium and Staphylococcus.Adult females were enriched for Erwinia,while adult males were enriched for Staphylococcus.In the gut of larvae,the function of bacterial symbionts is mainly related to fundamental energy metabolism including supplementation with assimilable nitrogen and efficient biomass utilization.In the gut of adults,bacterial symbionts likely played similar roles in reproduction.Those genera associated with the insect overwintering process were mainly relevant to energy metabolism.The predominant species found in the intestinal fungal communities mainly belong to the phyla Ascomycota and Basidiomycota.The genera Nakazawaea,Trichothecium,Aspergillus,Didymella,Villophora,and Auricularia are most prevalent in the gut of larvae.Adults harbored high proportions of Graphium.The fungal community structures found in gut of different sexes are similar.Fusarium is the most abundant genus and conserved in all development stages.Gut fungal communities showed notable variation in relative abundance during the overwintering stage.Fusarium and Nectriaceae were significantly increased in gut of overwintering mature larvae.The data indicates that Fusarium might play important roles in the survival of T.klimeschi,while Graphium plays an important role in the invasion and colonization of T.klimeschi.4.The major compound groups in T.klimeschi host and non-host tree that P.alba var.pyramidalis,Populus alba L,Populus tomentosa Carr,and Populus dakuanensis Hsu were aldehydes,esters,alcohols,ketones,phenols,terpenes and alkanes.T.klimeschi exhibited attraction to plant volatiles that nonanal,2-methyl-butanal,decanal,2-hydroxy-benzaldehyde,(Z)-3-hexen-1-ol benzoate,methyl benzoate,methyl salicylate and geraniol.The methyl benzoate was better in attraction of T.klimeschi than other tested volatiles.