Potato tubers were inoculated with various combinations of pathogen and antagonists in the laboratory, using methods based on those used by Grisham et al. (1983) to assess pathogenicity of P. erythroseptica. Tubers of cvs Pontiac and Russett Burbank were surface disinfested by soaking in 0.5% sodium hypochlorite for 3 min then rinsed three times in sterile distilled water (SDW). A core, 8mm in diameter and
25mm deep, was removed aseptically from each tuber using a cork borer, and a 5-mm diameter plug of P. erythroseptica isolate C2211 or of CMA alone (control)
was placed in the hole. A plug of T. harzianum or T. virens, or of CMA alone (control), was placed on the top of the first plug. The core of potato tissue was replaced and the wound sealed with vaseline. There were three replicate tubers of each cv. per treatment. Tubers were placed individually in paper bags and incubated at 20 C in the dark.