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Fire blight is a destructive and feared disease of apple and pear. Presently, antibiotics are the most effective materials used to prevent this tree-killing disease, but actions by the National Organic Standards Board have made this unlikely after 2014. Biocontrol of fire blight has been researched for decades, but has not been fully integrated within the context of organic production. <P> In 2009, at stakeholder request, we initiated research on non-antibiotic control of fire blight. Stakeholders identified two objectives: 1) development of effective non-antibiotic programs based on combinations of registered products, and 2) in apple, integration of these programs with bloom thinning.<P> In response, this project will: Objective 1: Under controlled conditions, characterize the abilities of three biological products to inhibit growth of the fire blight pathogen on stigmas and on nectaries of pome fruit flowers;<P> Objective 2: In experimental orchard trials, evaluate integrated non-antibiotic programs for fire blight control, and the degree to which the effectiveness of these programs is influenced by frequency of treatment applications; <P> Objective 3: In apple, evaluate the degree to which the early bloom treatments of lime sulfur and fish oil contribute to fire blight control, and how to integrate additional non-antibiotic treatments with the fruit thinning protocol; <P> Objective 4: Monitor commercial organic pear and apple orchards within Washington, California and Oregon for establishment of applied biocontrol agents in flowers, for the presence of the fire blight pathogen during bloom, and for the resulting severity of the disease; <P> Objective 5: Teach integrated, non-antibiotic fire blight control to the organic tree fruit Community of Practice.
Non-Technical Summary: <BR>Fire blight is a destructive and feared disease of apple and pear. Presently, antibiotics are the most effective materials used to prevent this tree-killing disease, but actions by the National Organic Standards Board could prohibit their use in organic agriculture beginning in 2014. Biological control of fire blight has been researched for decades, but has not been fully integrated within the context of organic production. In 2009, at stakeholder request, we initiated research on non-antibiotic control of fire blight. Stakeholders identified two objectives: 1) development of effective non-antibiotic programs based on combinations of registered products, and 2) in apple, integration of these programs with bloom thinning. In response, this project will a) characterize, under controlled conditions, the relative abilities of registered biologicals to inhibit the fire blight pathogen on floral surfaces; b) evaluate in experimental orchards integrated non-antibiotic programs for fire blight control and the effect of treatment frequency on program effectiveness; c) in apple, evaluate if early bloom thinning treatments contribute to fire blight control, and how to integrate additional non-antibiotic treatments with a bloom thinning protocol; and d) monitor commercial organic pear and apple orchards for establishment of biologicals in flowers, for the presence of the fire blight pathogen during bloom, and for the resulting severity of the disease. In this process, we will work closely with organic producers, and disseminate the data regionally and nationally via eOrganic webinars, an online course, and through traditional methods. Stakeholders will be involved continuously in on-farm research, data review, and critique of suggested recommendations. <P> Approach: <BR> In the planned research, we are hypothesizing that satisfactory, non-antibiotic suppression of fire blight can be achieved by integrating the varied properties of the registered biological control agents. We will document these varied properties by examining in a controlled environment the degree to which these agents suppress growth of the fire blight pathogen on stigmas (the pathogen's principle site of epiphytic increase) and on the floral nectary (the site of infection). Of particular interest is the location where A. pullulans, the yeast in Blossom Protect, most strongly inhibits the E. amylovora, which is poorly understood. Understanding the relative abilities of these biological agents to inhibit pathogen growth on floral stigmas and nectaries will aid in determining the need for and order of materials applied in a non-antibiotic, integrated program. In the field, variations of integrated programs will be evaluated with the goal of finding the most effective program with the least complexity and cost. In addition, in apple, we will evaluate the degree to which the early bloom thinning treatments contribute to fire blight control, and how to integrate additional non-antibiotic treatments with the bloom thinning protocol. All experiments will be replicated and the data collected on microbial populations and on fire blight disease will be subjected to analysis of variance. By the end of the project it is expected that all of the biological products used in this study will be available commercially, and thus an integrated disease control strategy can be implemented immediately by organic growers. This project also will devoted to outreach and to monitoring the fate of applied biological agents in commercial orchards. The primary purposes of this on-farm objective are to interact with advisors and growers to present and discuss approaches to non-antibiotic fire blight control, and to evaluate the performance of biocontrol products in the commercial-scale, organic environment. By sampling multiple orchards from three states, we expect to obtain data to characterize the variability in establishment of microbial agents among organic orchards employing similar practices. Variation among orchards in establishment of microbial agents in flowers will be followed up on to attempt to identify practices (e.g., time of treatment, sprayer speed, water volume, heat units after spraying, timing in relation to bloom thinning) that contribute to variation. In previous years, we have developed tools to measure if biological agents are establishing in flowers as intended, and we have also developed a molecular detection protocol to determine if and when the fire blight pathogen has become active within orchards. During these monitoring studies, we will communicate directly with growers and advisors, collect and evaluate samples of flowers from their orchards, and provide immediate feedback on our findings of biocontrol agent establishment and pathogen detection. Additional outreach will occur through eOrganic webinars and web-based publications as well as via traditional methods.