Assessment of Streptomyces spp. from Elms for Biological Control of Dutch Elm Disease. J. G. O’Brien, Graduate Research Assistant, University of Minnesota, St. Paul 55108. R. A. Blanchette, Assistant Professor of Forest Pathology, University of Minnesota, St. Paul 55108, and J. B. Sutherland, Assistant Professor, Department of Biological Sciences, Texas Tech University, Lubbock 79409. Plant Dis. 68:104-106. Accepted for publication 6 August 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-104.

A total of 433 actinomycete isolates obtained from phloem and xylem of American elm (Ulmus americana) were evaluated for antagonism in vitro against Ceratocystis ulmi, the causal agent of Dutch elm disease. Mycelial advance of a nonaggressive isolate of C. ulmi from Iowa or of an aggressive isolate from England was inhibited by an average of 75–76% by the actinomycetes. One isolate each of Streptomyces albovinaceus and S. griseus that inhibited various isolates of C. ulmi by 64–90% in vitro failed to prevent symptoms of Dutch elm disease when inoculated into elm samplings 1 wk before challenge with C. ulmi. Streptomyces isolates were recovered from 25–75% of inoculated elm saplings.