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Cultural Studies and Pathogenicity of Pseudocercospora fuligena, the Causal Agent of Black Leaf Mold of Tomato. G. L. Hartman, Plant Pathologist, Asian Vegetable Research and Development Center, P.O. Box 42, Shanhua, Tainan, Taiwan 74199, Republic of China. S. C. Chen, and T. C. Wang. Assistant Plant Pathologist, Tainan District Agriculture Improvement Station, Tainan, Taiwan; and Associate Specialist, Asian Vegetable Research and Development Center, P.O. Box 42, Shanhua, Tainan, Taiwan 74199, Republic of China. Plant Dis. 75:1060-1063. Accepted for publication 26 April 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source, The American Phytopathological Society, 1991. DOI: 10.1094/PD-75-1060.

Pseudocercospora fuligena was studied in pure culture and was inoculated on tomato plants under controlled conditions. Germ tubes were observed most frequently from the tip and basal cells of conidia. Free moisture was not necessary for conidia to germinate, and some conidia germinated at 91% relative humidity. Conidia did not germinate at or below 84.5% relative humidity. The fungus grew slowly in culture on four media tested. The optimum temperature for mycelial growth was 26 C, whereas no growth was observed at 34 C. On tomato-oatmeal agar, 6.1 × 10⁴ conidia per culture dish were produced after 3 wk, but conidia were not produced on potato-dextrose agar. Tomato plants inoculated with 5 × 10³ conidia per milliliter had 96% leaf area infected 14 days after inoculation. In cross-inoculation experiments, isolates from Solanum nigrum infected tomato, and isolates from tomato infected S. nigrum.