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are poised to occur with the increasingly wetter and warmer climate ( Frumhoff et al., 2007 Hayhoe et al., 2007 CBC News, 2014 CBC News, 2016 Robbins, 2019). It is predicted that more fire blight epidemics in the Mid-Atlantic, Northeastern, and Northwestern U.S. of more years with springs characterized by an extremely warm and wet weather that facilitates continuous blocks of 3 – 7 days with high fire blight infection potential according to developed prediction models, often reaching very high values in just a few days, and allowing 3 to 9 fire blight infection events during apple bloom ( Philion and Trapman, 2011 Cornell University, 2016 RIMpro-Erwinia, 2016). In the last 6 years, an alarming trend was recorded in the Northeastern and Mid-Atlantic U.S. Particularly, the Northeastern United States (U.S.) has experienced an increase in 0.09☌ in temperature and 10-mm in precipitation per decade, with a 70% rise in precipitation as heavy rain events ( Groisman et al., 2013 Kunkel et al., 2013). These results elucidate the role and importance of rootstock infections for apple tree survival, the presence of latent fire blight infections, and the valuable utility of molecular detection methods to assist apple tree removal after epidemics.įire blight, a bacterial disease of pome fruit trees, is becoming more damaging due to warmer and wetter weather patterns in spring ( Menzel et al., 2006 Keenan et al., 2014 Ault et al., 2015 Griffiths, 2021). amylovora rootstock strains showed slight variability in enzymatic activity, copper sensitivity, virulence, and exopolysaccharide production. However, the PCR from sampled edge rootstocks one year later showed no pathogen detections. One year later, 20.8 – 56.3% cankered rootstocks were detected on the edge trees and from zero to 35.4% dead edge trees were recorded. amylovora detection rates of 10.7 – 45.3% in asymptomatic rootstocks on the edge trees immediately surrounding visibly infected i.e. In the first year, most of the orchards showed E. amylovora strains collected from these seven orchards and other orchards in New York were characterized. Each infection focus consisted of central rootstock-blighted tree and the nearest surrounding edge trees showing no rootstock blight. Rootstock canker incidence and tree death were rated in selected infection foci on seven commercial apple orchards in New York. amylovora in symptomatic and asymptomatic rootstocks for two years.

To determine apple tree losses caused by fire blight rootstock infections, PCR was used to detect E. Accurate fire blight diagnosis is necessary to inform the complete removal of infected trees from the orchard and help replanting efforts while preventing further pathogen dissemination. amylovora in apple rootstocks is essential because this pathogen also causes asymptomatic infections. An accurate diagnosis of trunk and rootstock blight is a top challenge for apple growers because fire blight cankers can be visually misdiagnosed with cankers caused by less frequent Oomycete and fungal pathogens (e.g., Phytophthora spp., Botryosphaeria dothidea, B. Cankers can girdle the trunk, branches and rootstock leading to tree death and production losses, especially significant in high-density orchards.

Fire blight cankers are infected zones of dead bark on perennial branches, trunk, or rootstock that develop after fire blight pathogen Erwinia amylovora invades wood. 4Department of Entomology and Plant Pathology, Institute of Agriculture, University of Tennessee, Knoxville, TN, United StatesĪ devastating outcome of fire blight in apple trees is the infection of rootstock, which leads to canker development.3Plant Pathology Laboratory, Hudson Valley Research Laboratory, School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Highland, NY, United States.2Plant Pathology Laboratory, Irrigated Agriculture Research and Extension Center, College of Agricultural, Human, and Natural Resource Sciences, Washington State University, Prosser, WA, United States.Agricultural Research and Extension Center, School of Plant and Environmental Sciences, Virginia Polytechnic Institute and State University, Winchester, VA, United States Aćimović 1*, Ricardo Delgado Santander 2,3, Christopher L.