Study On The Eucalyptus Dieback

The forest of Eucalyptus is the main source of forest in the south of China. There are ten thousands to hundred thousands mu Eucalyptus which are cultivated stand by stand in some counties in Fujian , such as Quanzhou County ,Zhangzhou County and Sanming County etc .Eucalyptus Dieback is one of quarantined forestry plant disease .It often occurs in nursery-grown plants and the coppice shoot under four years,in the same time ,it also infect sprouting trees.The disease was not recorded 1999 ago in Fujian Province .But in July 1997,it was found in the forest-experimental station of Tuangshi in Yong'an County .Fujian , which has made hundreds mu Eucalyptus dry to die .The Forestry Quarantine Station of Fujian Province pay great attention to it ,and the civil forestry department organize some one to extinguish it at once . But they can't lay down effectively controlling measure ,because they are lack of understanding and studying on the feature of the occurrence and development about this disease in our province .So that it still extend in the forest in Yong'an County .according to the founding of the Forestry Quarantine Station of Sanming County in 2000.Therefore, we have made the primary study on the biological characteristics of the pathogen ,the rule of the occurrence and development ,the measuring house toxicity on pathogen ,the multiple control of the disease and the determinaton of the loss of the disease .The results are showed as follow:1 The biological characteristics of the pathogenThe pathogen of Eucalyptus Dieback is Cylindrocladium quinqueseptatum Figueredo. It has a rather strict demand of nutrition and circumstance .It grows better in medium containing amylum or juice of the leaves of Eucalyptus with agar. If adds different C or N to the medium , it can promote the growth of the hypha obviously . The growth of the hypha demand higher moisture ,but the temperature that be suit to grow is from 15 to 35 degrees centigrade .The acidic environment is benefit to sporogenesis and the spore germination ,meanwhile , the basic one is good for the growth of hypha .The dark condition is benefit to nutrition growth ,but the reproductive growth is object to that .2 The rule of the occurrence and development of this diseaseEstablishing the standard sample to observe the disease all the year .It mainly endangers the leaves and branches ,and mostly begins from the lower branches ,up to the top . It least begains on the lower ,middle and utter crown at the same time .The pathogen can invade the leaves through no injuried cutex or wounds .Its wintering ground is the soil or the deblade ,as mycelia and immature sporocarp. The spores diffuse from May , and the hightime is from July to October ,mainly spreaded by rain and wind .Higher temperature and moisture is benefit the disease to extend .3 The measuring of house toxicity on the pathogenAdopting the way of measuring the grow speed in the toxic medium ,we choose eight different usual fungicides to determinat their toxicity. The result indicated: the relations between the toxicity of different fungicides and the concentration is negative correlation. The fungicidal effect of Doconct is the highest ,the second was Tuzet and Oxandixyl & Mancozeb ,the third was Zineb and Mancozeb Sulfur, Kasugamycin was the lowest.4 Multiple control of diseaseThe result of field test indicated: the relations between different fungicides and its concentration is significance .Because the effect of Oxandixyl & Mancozeb and Daconil are the best ,so we advise adopting them to spray in practice .In the same time ,if choosing nursing measures, the best is weeding and manurance .The Calcium mangne-sium phosphate fertilizer acts as basal application of fertilizer ,and the Carbamide as refertilizer. Weeding the leaves infecting the disease at the preliminary period ,so that it can lighten the degree of the disease.5 The estimation of the loss of the diseaseIn the seriously infected stand ,adopting canonical sample and analysis in stems ,the effects of different inf...