Submitted to: Washington State Horticulture Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 17, 2012
Publication Date: N/A
Technical Abstract: Fire blight infection is generally initiated in flowers, and thus, research has been directed to the biology and microbial ecology of flowers as related to this disease. In addition to investigations involving apple and pear flowers, Manchurian crab apple (Malus manchurica), closely related to apple (Malus domestica), was developed as a laboratory research model because the trees are easily manipulated to produce flowers year round. The critical flower parts in disease development are the stigma, where the causal bacterium becomes established epiphytically; and the hypathium, where moisture leads to infection. Studies have indicated that a diversity of bacteria and yeasts naturally colonize both stigmas and hypanthia. Beneficial bacteria are especially adapted to young stigmas, where they are more effective than yeasts in suppressing the disease bacterium; yeasts, though, are particularly adapted to the hypanthium and tend to dominate on older flowers. These observations have implications for the effective timing of commercial biocontrol treatments involving beneficial bacterial and yeast strains. In addition to presenting past studies relevant to fire blight management in organic orchards, proposed future strategies for optimizing biological control and integrating it with other control approaches were discussed.