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Etiology

Pathogenicity of Botrytis Species on Onion Umbels and Scapes Under Controlled Conditions. G. R. Ramsey, Research assistant, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853; J. W. Lorbeer, professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853. Phytopathology 76:604-612. Accepted for publication 11 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-604.

Botrytis squamosa blighted a higher percentage of onion florets than either B. cinerea or B. allii when umbels with all the florets unopen or umbels with approximately two-thirds of the florets open were inoculated in a dew chamber. B. byssoidea was nonpathogenic under these conditions. B. squamosa blighted more florets than B. cinerea or B. allii at all inoculum concentrations tested. There were no differences in percentages of blighted florets for the open-pollinated onion cultivars Early Yellow Globe. Early Yellow Medium, and Italian Red and the hybrid cultivars Ontario M and Sentinel. Onion umbels covered by the spathe were susceptible only to B. squamosa. The susceptibility of open umbels to either B. squamosa, B. cinerea, or B. allii increased as the proportion of open to unopen florets at the time of inoculation was increased. Open florets were more susceptible than were unopen florets or immature seed capsules. Blighting was not increased by inoculating two of the pathogens together.