| In recent years Oxalis corymbosa DC. prodr. became more prevalent in the dry fanning inGuizhou. Also, it became a kind of virulent weed in lawn and in garden plot of most southern areain China. The research aimed to know the biological characteristics of the pathogenic fungi(Pseudocercospora oxalidis Goh & Hsieh) on Oxalis corymbosa, ultimately to be helpful incontrolling of this weed by using its pathogenic fungi.The pathogen only parasites the leaves of hosts. Leaf spots ampigenous, subcircular, 2.0-9.0mm wide, often confluent, pale brown, to center brown, margin surrounded by a dark brown line, with pale yellowish brown halo on the upper surface, on the lower surface, pale greyish white to greenish yellow-brown on the lower surface. Fruiting hyaline, chiefly epigenous. Stromata none or only a few achromatous globose cells. Conidiophores short, solitary or facicular on the globose cells or endogenous mycelia, subhyaline, often wide at the base, straight, not branched, 1 geniculate, cylinderic to conical or subtruncate at the apex, none septa, 3.0-20.0×2.0-4.0μm. Conidia narrowlly obcapitulate to cylinderic, subhyaline, straight or curved, acute to obtuse at the apex, obconical to subtruncate at the base, 2-9 septate, 20.0-86.5×2.0-3.0μm. Concluding that the pathogen is Pseudocercospora oxalidis Goh & Hsieh. The pathogen was obtained using separating and purifying method. The code of the pathogenic fungi was JH-016-01.The biological characteristics of the pathogen were measured in the study. One of the most optimum media for Pseudocercospora oxalidis growth was Oxalis corymbosa leaf decocting plus glucose disk medium. V8 juice agar and Richard's medium were also propitious to the pathogenic fungi. For the growth of the pathogen, the favorable pH ranged in 3~12 with the optimum pH 4-6, the favorable temperature was between 20~25℃, the same for conidial germination. The thermal death point of the fungi was at 55℃ in10min. Among the tested carbon and nitrogen resources,...
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