![]() ![]() It has appendages called flagella that allow it to swim in water. Causal Organismįire blight is caused by Erwinia amylovora, a gram-negative, rod-shaped bacterium. In apples, the danger of serious economic damage by fire blight has increased due to the adoption of high density orchard systems and widespread cultivation of susceptible scions on highly susceptible rootstocks.įunding for this article was provided by a USDA NIFA OREI grant for the project Implementation of Non-Antibiotic Programs for Fire Blight Control in Organic Apple and Pear in the Western United States. Fire blight has always been a serious disease of pear, and the susceptibility of this species to fire blight is one of the reasons that United States pear production is concentrated in semi-arid regions of western states where dry summers lessen the impact of the disease. Occasionally, however, the damage is done during primary bloom. In the western United States, most common infections ordinarily occur on secondary blooms in May or June during the weeks following petal fall. The fire blight pathogen, Erwinia amylovora, is native to North America. For example, a 10% incidence of rootstock blight in a 4-year old apple orchard can result in losses up to $3,500 per acre (Norelli et al., 2003). Even minor disease outbreaks can be significant. In the Pacific Northwest and northern California, there have been minor outbreaks annually since 1991 with at least some production districts experiencing major outbreaks every 3 to 4 years. While fire blight rarely kills an entire orchard in the western states, the disease and its control still cause significant economic losses. Nationally, annual losses to fire blight and the costs of control are estimated at over $100 million (Norelli et al., 2003). Tianna DuPont, Washington State Universityĭavid Granatstein, Washington State University Overviewįire blight is an important disease affecting pear and apple.
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