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Disease Note.

Occurrence of Cercospora zebrina on Subterranean Clover in South Texas.. R. G. Pratt, USDA, ARS, FRU, Box 5367, Mississippi State 39762. W. R. Ocumpaugh, Texas Agricultural Experiment Station, Beeville 78102. Plant Dis. 78:1010. Accepted for publication 12 July 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1010C.

Symptoms of Cercospora leaf spot were observed on numerous cultivars of subterranean clover (Trifolium subierranewn L.) (subclover) at Beeville, Texas, from 1988 to 1990. Symptoms included tan lesions with dark borders on leaves, girdling lesions on petioles, and nongirdling, elongate lesions on stems. Isolates obtained by transfers of conidia from sporulating lesions were identified as Cercospora zebrina Pass, by coni-dium and conidiophore morphology (1). Leaves of six cultivars of sub-clover and 10 cultivars of arrowleaf, berseem, crimson, red, and white clovers were inoculated with aqueous suspensions of conidia of six isolates. Symptoms developed consistently only on subclover. Four cultivars of T. s. subterraneum developed numerous lesions in response to all iso lates, while cultivars of T. s. brachycolycinum (Clare) and T. s. yannini-cum (Yarloop) developed few or none. Results indicate that C. zebrina from subclover in south Texas is host-specialized in pathogenicity and that host resistance is available. This is the first known occurrence of this disease in North America west of Mississippi (1).

Reference: (I) R. G. Pratt. Phytopathology 74:1152, 1984.