Study On The Development Rule, Loss Estimation And Control Criterion Of The Eucalyptus Dieback

The forest of eucalyptus is the main source of forest in the south of China. It is one of the quick growing wood species and planted widely. There are tens of thousands hectares artificial forests of Eucalyptus which are cultivated stand by stand in Fujian. Eucalyptus is developing rapidly. However, because of cultivation of large area pure forests and inadequate management, the growth environment of Eucalyptus worsens and it is favorable to the emergence of the disease. The disease was found for the first time in the forest-experimental station of Tuanshi in Yong'an County in Fujian province in July 1999.The disease caused 125.5 hm~2 of eucalyptuses to wither or die, and brought great loss to production of forestry. For this reason, the forestry department released the epidemic situation to notify. But they can't lay down effective and reasonable controlling measures, because they are lack of understanding and studying on the feature of the occurrence, development and controlling measures about this disease in Fujian Province. So once the disease diffuse and spread, people will not know what to do and how to do. Therefore, controlling disease have come the key problem badly in need of solution.In view of the above reason, this text studied on the rule of the occurrence and development, the indoor virulence bioassay, the field test of germicide, the test of managing forest measures, loss estimation, economic injury level and economic threshold. The results are showed as follow:1. The rule of the occurrence and development of the diseaseThis pathogen mainly survives the winter on the fallen leaf and the soil in the form of fruitbody or hypha. With the temperature and rainfall increasing in the next year, the fruitbody or hypha which survive the winter begin to generate new conidium and spread among forest through wind and rain. Conidia mainly invade from the natural orifice or wound on the back of the new leaf, and rely mainly on the natural orifice. After 3 days to 10 days, the host will have illness. It mainly begins from the lower branches of the tree up to the top. The disease generally starts in the last ten days of April or early May, peak period generally appears in July and August, and gentle gradually in September, then the disease will stop developing in about mid-November.The emergence and development of the disease is closely related to local climatic conditions. To a great extent, the temperature, rainfall and relative humidity determine the development degree of this disease, high temperature and moisture is benefit to the disease to diffuse. There are differences of morbidity degree among the different crown layers, ages of tree and breeds.2. The loss estimation of the disease...