Epiphytic Pseudomonas syringae on Dry Beans Treated with Copper-Based Bactericides

The response of epiphytic populations of Pseudomonas syringae and other bacteria on dry bean plants to four copper-based bactericides was evaluated. The bactericides showed little difference in efficacy, but epiphytic populations on pinto bean leaflets, flowers, and pods were occasionally reduced when compared to populations on non-treated control plants, especially after repeated bactericide applications. Although there was a trend toward a relationship between epiphytic leaflet and flower populations, there were cases where P. syringae was undetected on one organ but abundant in samples from the other organ. P. syringae pv. syringae strains recovered from epiphytic populations demonstrated much greater copper resistance than did strains of P. syringae pv. phaseolicola, as measured by growth on media amended with cupric hydroxide. This difference between the pathovars may have implications for integrated pest management strategies.