Epidemic of Leaf Mold Caused by Fulvia fulva on Field-grown Tomatoes in Iowa. M. L. Gleason, Department of Plant Pathology, Iowa State University, Ames 50011. S. K. Parker, Department of Plant Pathology, Iowa State University, Ames 50011. Plant Dis. 79:538. Accepted for publication 3 April 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0538C.
An epidemic of leaf mold was observed on five cultivars of staked, fresh-market tomatoes in a commercial planting located in a river valley near Auburn, Ia., on 14 July 1994, 6 weeks after transplanting. Approximately 30% of leaves on the lower halves of plants displayed characteristic, pale green to yellow spots with indefinite margins on upper leaf surfaces and buff to olive green spore masses on the undersides of leaves. Leaf necrosis caused by the epidemic was estimated at 5% of total leaf area on 14 July and 40% on 18 August. Fulvia fulva (Cooke) Cif. (syn. Cladosporium fulvum Cooke) was isolated consistently from sporulating lesions other pathogenic fungi were not isolated. Single-spore isolates were obtained and increased on potato-dextrose agar (PDA). In culture, the fungus formed slow-growing, raised clumps of dark-brown mycelium. Colonies were covered with tufts of light grayish green aerial mycelium that eventually produced tan-colored spore masses. The upper leaf surfaces of 4- and 8-week-old tomatoes (cv. New Yorker) were sprayed with an aqueous suspension of conidia prepared from 3-week-old cultures. Inoculated plants were incubated on a greenhouse bench at 100% relative humidity and 200C for 48 h, then 12 h/night for the next 3 days. Chlorotic lesions and white mycelial tufts were visible 1 week after inoculation and tan conidial masses after 2 weeks. The fungus was reisolated from these conidial masses. Although leaf mold is typically a disease of greenhouse-grown tomatoes, this is the first report of a leaf mold epidemic on field-grown tomatoes in the north central region of the United States.