2022) and when humidity is high in the spring the pathogen ooz.es out of these cankers (Figure 5). In 7 to 62% of cankers active cells survive the winter (van der Zwet and Beer 1991, Santander et al. Signs and SymptomsĮrwinia amylovora overwinters in the living tissue around canker margins (Biggs 1994, Teviotdale 2011). amylovora has a wide host range within Rosacea and Rubus with reports on about 200 species including crab apple, hawthorn, mountain ash and Bradford pear (Momol and Aldwincklke 2000). Host RangeĬonsidered a problem for apple and pear, E. Above 95° F cell density on and in the plant can actually decline (Pusey and Curry 2004). At air temperatures above 70° F, the rate of cell division increases rapidly and is fastest at 80° F. Cell division is minimal below 50° F, and relatively slow at air temperatures between 50 to 70° F. The bacterium grows by splitting its cells and this rate of division is regulated by temperature.
Casual Organismįire blight is caused by Erwinia amylovora, a gram-negative, rod-shaped bacterium. In Washington there have been minor outbreaks annually since 1991 and serious damage in about 5 to 10 percent of orchards in 1993, 1997, 1998, 2005, 2009, 2012, 2015, 2016, 20. Increased acreage of highly susceptible apple varieties on highly susceptible rootstocks has increased the danger that infected blocks will suffer significant damage. Infections commonly occur during bloom or on late blooms during the three weeks following petal fall. updated April 13, 2023.įire blight is an important disease affecting pear and apple. By Tianna DuPont, Associate Professor, Washington State University Tim Smith, Washington State University Tree Fruit Extension Specialist Emeritus Ken Johnson, Professor of Plant Pathology Oregon State University Youfu Zhao, Washington State University.
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