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Ecology and Epidemiology

Aberrant Behavior of Mycosphaerella citri on Freeze-Killed Citrus Leaf Tissue and Its Taxonomic and Epidemiologic Implications. J. O. Whiteside, Professor of plant pathology, University of Florida, Institute of Food and Agricultural Sciences, Agricultural Research and Education Center, Lake Alfred 33850; Phytopathology 71:1108-1110. Accepted for publication 26 February 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1108.

Conidia of Mycosphaerella citri normally develop only on single conidiophores produced sparsely from extramatrical hyphae on citrus leaves, and ascocarps usually develop only on decomposing fallen leaves. No fruiting structures were observed on or in greasy spot lesions on living leaves. However, when leaves carrying latent infections of M. citri were locally injured by freezing, the fungus sometimes produced fasciculate conidiophores and ascocarps on the resulting necrotic spots and patches while the leaves were still alive and attached to the tree. Similar fasciculate conidiophores were described previously for Cercospora citri-grisea on necrotic citrus leaf tissue. Therefore, C. citri-grisea is a binomial for the anamorph of M. citri. The number of airborne conidia released from fasciculate conidiophores on freeze-induced leaf spots was infinitesimal compared with the number of ascospores released from ascocarps on fallen leaves.