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Disease Note

First Report of Ulocladium cucurbitae on Cucumber in California. K. F. Sims, San Diego County Department of Agriculture, 5555 Overland Ave., San Diego, CA 92123. T. E. Tidwell, and D. G. Fogle. California Department of Food and Agriculture, 1220 N Street, Sacramento 95814. Plant Dis. 75:863. Accepted for publication 18 April 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0863D.

A leaf spot disease was observed on Dasher II cucumber (Cucumis sativus L.) in commercial plantings in San Diego County, California. Symptoms consisted of irregular brown necrotic spots that darkened with age. Spots were delimited by major veins, but not by smaller veins, and measured 0.5-2 cm in diameter. Isolations from leaf spots yielded what appeared to be a mixture of Ulocladium and Alternaria cultures. Single-spore cultures revealed that both spore types belonged to the same fungus, U. cucurbitae (Letendre & Roumeguere) E. Simmons (1). Single-spore cultures from ulocladioid spores were used to confirm pathogenicity of the fungus on Dasher II cucumber in the greenhouse. After 8 days, the inoculated cucumbers had symptoms identical to those of the original plants, and cultures of the reisolated fungus yielded both the alternarioid and ulocladioid spore types. On the basis of symptoms and fungal identification, this is the same disease reported by Zitter and Hsu in New York (2). This is the first report of the disease in California.

References: (1) E. G. Simmons. Mycotaxon 14:44, 1982. (2) T. A. Zitter and L. W. Hsu. Plant Dis. 74:824, 1990.