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Disease Note

Phaeosphaeria Leaf Spot of Maize in Florida. M. L. Carson, USDA-ARS, Department of Plant Pathology, and M. M. Goodman, North Carolina State University, Raleigh 27695; and D. A. Glawe, Department of Crop Science, North Carolina State University, Raleigh 27695; and Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 75:968. Accepted for publication 22 April 1991. DOI: 10.1094/PD-75-0968E.


Pseudothecia of the fungus Phaeosphaeria maydis (Henn.) Rane, Payak, & Renfro (1) (= Leptosphaeria zea-maydis Saccas; Metasphaeria maydis (Henn.) Hohnel) were found in lesions on leaves of maize (Zea mays L.) from winter breeding nurseries in the Homestead, Florida, area during late December 1990. Lesions were typically round to oval, light tan or "bleached" with distinct brown margins, 0.5-2.0 cm in diameter, and mostly scattered on all leaves of mature (>30 days past flowering) plants. The inbred line B73 and its derivatives appeared to be affected most severely, although both susceptibility and resistance were observed for a wide array of genotypes in several nurseries. Pseudothecia were dark, spherical to subglobose, immersed in the leaf tissue, and 110-140 µm wide X 118-140 µm high. Asci were bitunicate, clavate, or cylindrical and 65-88 X 10-13 µm, with eight biseriate to overlapping uniseriate ascospores. Ascospores were three-septate, hyaline, usually guttulate, and 19-25 X 5 µm, with the second cell distinctly swollen. This is the first report of this disease of maize in the continental United States. Cultures of the fungus have been deposited with the American Type Culture Collection.

Reference: (1) M. S. Rane et al. Bull. Indian Phytopathol. Soc. 3:7, 1966.