VIEW ARTICLE

Disease Control and Pest Management

Naturally Occurring Tolerance in Isolates of Ceratocystis ulmi to Methyl 2-Benzimidazolecarbamate Hydrochloride. L. R. Schreiber, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Delaware, Ohio 43015; A. M. Townsend, Research Geneticist, Agricultural Research Service, U.S. Department of Agriculture, Delaware, Ohio 43015. Phytopathology 66:225-227. Accepted for publication 26 August 1975. DOI: 10.1094/Phyto-66-225.

Twenty-nine isolates of Ceratocystis ulmi from various locations throughout the United States were tested for tolerance to methyl 2-benzimidazolecarbamate hydrochloride (MBC-HCl). Tolerance was measured by the growth of the isolates in a series of petri plates containing potato-dextrose agar amended with several concentrations of MBC-HCl. Six isolates (from Colorado, Massachusetts, New York, North Carolina, Tennessee, and Virginia) grew on agar amended with MBC-HCl concentrations ranging from 1 to 1,000 µg/g, whereas growth of the other 23 isolates was inhibited by 1 µg/g. The chemical tolerance of C. ulmi to MBC-HCl occurred naturally, and did not arise following exposure to MBC-HCl or other benzimidazole compounds.