Study On Fungi Associated With Elm Bark Beetles In Xinjiang

The elm is an important greening tree species and afforestation species in Xinjiang, and playes a huge ecological role in sand-fixation and erosion prevention. In recent years, great economic losses and ecological damages have been caused by the bark beetle. Compared with the status of international research, the understanding and the pest control of bark beetles still remained the forest pest, lacking of understanding of the system in China. And this would affect the sustainable management of the pest. In this research, the aim was to obtain a large number of fungi, find a number of new taxa associated with the bark beetles, and explore the role that the associated fungi play in the plant-beetle-associated fungi system through a series of studies. It is essential, therefore, to provide the basic data for the bark beetle pollution prevention and the healthy ecological elm foster. In addition, although the native species of elms have resistance to the dutch elm disease in Xinjiang, a variety of elms (Ulmus densa Litv., U. laevis Pall. F1. Ross., etc.) were introduced from Europe and Central Asia in recent years. If the native bark beetles can carry the pathogen of dutch elm disease, the risk of intrusion will be increased. This study can monitor whether this disease has already invaded our country.From the spring of 2009, the areas where Scolytus schevyrewi occured badly were surveyed in Xinjiang, and the diseased elms attacked by S. schevyrewi where the elm wilt and death occurred universally were collected and transported to the laboratory. In addition, the weakening and dying plants as well as apparently healthy plants have been main targets to be attacked by S. schevyrewi, which can carry the pathogen of dutch elm disease, in all sites. The number of elms infected by bark beetles was large and the tree mortality was severe, especially for the shelterbelt, whereas, was few incidence in natural elms. The damage by other pests and freeze injury often accompanied with bark beetles infection.26 genera and 2 unidentified fungi isolated from diseased elms attacked by Scolytus schevyrewi were purified and identified. Fusarium was predominant during the sampling. It occurred in a higher percentage of about 84.72%,6.03%,36.37% and 64.86%. from infested elm wood, adults, larva and the excretion of larva The species of Fusarium was identified as F. solani by morphology and molecular biology.15 genera and 1 unidentified fungi were isolated from healthy Ulmus pumila samples. Tolura and Sphaeropsi were predominant, and the isolation rates were:26.94% and 25.98%.In addition, one sample of Ulmus densa attacked by the bark beetle, which was not yet identified, was collected in Fukang.15 genera and 2 unidentified fungi were isolated from it. The result showed that Geosmithia was dominative, and the isolation rates of diseased wood attacked by bark beetles, the mycelium in gallery system of elms and the body wall of the bark beetle were:72.7%,100%,88.54%.In this paper, some strains of Geosmithia, which is a kind of mitosporic filamentous fungi typically associated with phloeophagous bark beetles world-wide, were obtained from the gallery system of bark beetles in Ulmus densa. One of the islolates was studied using morphology and molecular biology, and it was confirmed that the new record genus-species from Mainland of China was:G. pallid (G. Sm.) Kolarik, Kubatova & Pazoutova. Furthermore the other isolate in galleris was identified as a new record genus-species in china: Neoscytalidium novaehollandiae Pavlic, Burgess, M.J. Wingfield.The pathogenicity of Fusarium solani, which was a dominant species of fungi associated with Scolytus schevyrewi, was tested on Ulmus pumila. The results showed that the inoculated strain caused significant lesion of inner bark of host plant.The composition and predominant populations of mycoflora were different, which suggested the composition and variety of the fungi were likely related to bark beetles. It is expected that the information will be useful in further clarifying the biological characteristics of bark beetles as well as symbiotic relationship between the beetle and fungi.This study provided basic data for pest and disease prevention of elms. Otherwise Ophiostoma ulmi=Ceratocystis ulmi and Ophiostoma novo-ulmi, the pathogen of dutch elm disease, were not isolated in this study. This indicated that the elms were attacked by bark beetles in Xinjiang, but the dutch elm disease was not discovered.