Abstract: The blight disease of tungoil trees is generally called tungoil tree pestilence. It is a vascular disease caused by a new formae speciale of Fusarium oxysporum, Fusarium oxysporum Schl. f. sp. aleuritidis f. sp. Nov. This disease is found in the provinces of Jiangxi, Zhejiang, Hunan, Sichuan, etc. in our country. It usually attacks the 3-4-year-old tungoil trees, or the older ones. The pathogen enters the host plant through its roots, multiplies in its vessels and gradually extends upwards to parts of the plant above ground, thus causing the whole or half of the plant to die. The highest infected rate of tungoil trees may reach 60-90%- It is a destructive disease and seriously threatens the production of tungoil trees.A great number of the pathogene has been isolated and cultured, inoculated and reisolated. It belongs to Fusarium oxysporum according to its morphological features.Host plants of the pathogen include 64 species in 29 families. No other species are attacked. In view of its highly selective pathogenicity to host and the rule for international nomenclature that the name of the formae Speciales should be correspondent to the name of the host, the author suggests that the pathogen ontungoil trees should be Fusarium oxysporum Schl. f. sp- aleuritidis /. sp. Nov.The spores of the pathogen can germinate normally in clean water with a pH value of 3-12. When the relative humidity is lower than 80%, spores fail to germinate. Optimun temperature for germination is 25-30 C. Carbonic, phosphorous nutrient elements are not especially required for the growth of the pathogen, but nitrogen is necessary.