Assaying Bactericide Efficacy Against Pseudomonads on Bean Leaf Surfaces. H. F. Schwartz, Associate Professor, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523. M. S. McMillan, Research Associate, Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523. Plant Dis. 73:822-824. Accepted for publication 16 May 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0822.

Populations of a pathogenic strain of Pseudomonas syringae pv. phaseolicola that had been artificially established on greenhouse-grown pinto bean plants (Phaseolus vulgaris) were exposed to several formulations and rates of copper-based bactericides under controlled conditions to measure pesticide efficacy. New formulations of cupric hydroxide and mixtures of copper oxychloride significantly (P <0.05) reduced these populations. Naturally occurring populations of epiphytic pseudomonads on bean leaves were significantly (P <0.05) reduced and bean yields were significantly (P <0.05) increased by applications of copper-based pesticides in the field in eastern Colorado. Results obtained by the two procedures were similar. The assay technique and its applications are discussed.

Keyword(s): bacterial brown spot, disease control, Pseudomonas syringae pv. syringae