The Analysis Of Outbreak Factors And Control Of Dwarf Mistletoe (Arceuthobium Sichuanense) In Qinghai Province

The dwarf mistletoe(Arceuthobium sichuanense) was one of the semi-parasitic seed plants which had the ability of photosynthesis and reproduction in Viscaceae Arceuthobium. The dwarf mistletoe infection in recent years led to decline of the host spruce timber volume growth, increase of the host mortality and stop of the host update. Now it has been one of the major diseases which seriously threaten the spruce forest in Qinghai province. The thesis focused on the spruce forest infected by dwarf mistletoe of Xian Mi forest in Qinghai, transect survey was used to reveal the spatial distribution pattern of dwarf mistletoe. Standard samples were set to pick up the outbreak key factors of dwarf mistletoe. Ethephon was chosen to control the dwarf mistletoe in field and made clear of the effect, concentration and time of ethephon control. The infected branches were collected for histological observation and analysis of the inside mechanism of the ethephon to dwarf mistletoe. The results were as follows:Transect survey method was chosen to investigate the typical sub-compartment. By analyzing the disease incidence, it was found that the hazard of. Arceuthobium sichuanense in the sub-compartment gradually increasing from the foot to the top of hill. Then all crown-third DMR distribution of the host were counted, it was figured out Arceuthobium sichuanense prefer to grow from lower crown to the upper crown in the single host.Fourty standard samples were set in Xianmi forest, taking DMI, mean DBH, mean height, stand type, mingle index, herb cover, moss depth as response variable, taking canopy density, slope, elevation as environmental factor. It was ascertained that crown density, slope, slope position, elevation and stand type were the main factors which had an effect on the outbreak of Arceuthobium sichuanense by using RDA analysis. The canopy density had a significantly negative correlation with the incidence of dwarf mistletoe. The slope and elevation had a significantly positive correlation with the incidence of dwarf mistletoe. The stand composition had an effect on the occurrence of dwarf mistletoe, dwarf mistletoe do less harmful in the higher mingling forest.Different diluted40%ethephon were applied to the shoot, bud and fruit of A. sichuanense continuously. The result showed that dilution of1:200had best control effect on the period of flower and fruit. Applying diesel oil as a solvent for different concentration of40%ethephon to flower and fruit of A.sichuancnse,it was found that dilution of1:200had better control effect than any other solutions, meanwhile it was harmless to the spruce and the plant under the tree.Branches treated by ethephon were continuously sampled, then the sections were observed though optical microscope. The staining results showed that cthephone had an effect on the endophytic system growing in the phloem of host spruce, to dissociate the tissue and make the shoot abscission.