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Etiology

Variability in Aggressiveness, Recovery, and Cultural Characteristics of Isolates of Ceratocystis ulmi. Lawrence R. Schreiber, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Delaware, Ohio 43015; Alden M. Townsend, Research Geneticist, Agricultural Research Service, U.S. Department of Agriculture, Delaware, Ohio 43015. Phytopathology 66:239-244. Accepted for publication 9 September 1975. DOI: 10.1094/Phyto-66-239.

Seedlings of several elm species were inoculated with isolates of Ceratocystis ulmi from various geographic areas in the United States. The isolates caused different amounts of foliar and vascular symptoms regardless of seedling species, age, or the environment. The more aggressive isolates were recovered from Ulmus pumila more frequently than the less aggressive ones, but all were recovered with about equal frequency from U. americana. With some exceptions, the more aggressive isolates grew more rapidly on agar media, were intermediate in mycelial habit between appressed and fluffy, and produced more coremia on wood of both U. americana and U. pumila.