Cultural practices include planting less susceptible cultivars and resistant rootstocks, management of the orchard environment (e.g., proper fertilization, irrigation, and tree training), and orchard sanitation (e.g., cutting and removing infected tissue). 2006).Ĭurrent fire blight management tactics focus on the minimization of inoculum in the orchard through cultural practices and the use of spray treatments to prevent infection (Norelli et al. The pathogen may then progress to the supporting branches and advance further to the main limbs, trunk, and rootstock collar and crown (Gowda and Goodman 1970 Momol et al. After colonizing the flowers, the bacterial cells invade the intercellular spaces of the cortical parenchyma and reach the vascular system (Van Der Zwet and Keil 1979). 1972 Gowda and Goodman 1970 Kharadi and Sundin 2021 Koczan et al. ![]() In addition, the bacteria can spread within an infected plant (Aldwinckle and Preczewski 1979 Bogs et al. Secondary inoculum produced on infected flowers can then be spread to other flowers and/or other plant parts and cause infections later in the growing season. Flower infections occur when warm conditions favor multiplication of the bacteria on the floral stigma and moisture from rain or dew wash bacteria down into the floral cup where it can enter the plant through openings termed ‘nectarthodes’. ![]() Shoot infections are more common in humid summer climates such as the eastern United States. In the Western United States, the majority of infections occur in flowers, however bacteria can also enter young, tender shoots through wounds caused by wind, hail, or insects. 2003a).įire blight is initiated when overwintering cankers exude bacteria that are then disseminated by insects and/or rain. Losses to fire blight and cost of control in the United States are estimated to reach over $100 million annually (Busdieker-Jesse et al. In the United States the disease has been known as a serious problem in apple and other pome fruits for over 200 years (Baker 1971 Van Der Zwet and Keil 1979). In one of five experiments cutting which left a 13 cm stub distal to structural wood significantly reduced the number of cankers on structural wood compared to flush cut or 4 cm stubs.įire blight, Erwinia amylovora, is the most destructive bacterial disease in apple orchards in the United States and many other countries (Vanneste 2000). Breaking off diseased branches by hand provided a rapid removal method, but it resulted in a greater number of cankers in the orchard at the end of the season. ![]() Elimination of cutting tool sanitation did not result in more cankers than the standard practice. Aggressive removal, defined as BMP but branches removed approximately 76 cm from the proximal edge of visibly cankered tissue, generally did not improve the standard practice. This practice significantly reduced the number of new systemically-caused symptoms compared to the no-treatment control in seven of nine experiments with significant reductions in five experiments. The standard best management practice (BMP) for removing fire blight was branch removal at 30 cm below the proximal edge of visibly cankered tissue with sanitized loppers. Removal treatments resulted in fewer additional cankers compared to the no-treatment control in most trial sites and years. Fire blight removal resulted in reductions of rootstock blight and tree death. Removal methods included pruning at varying distances from visible symptoms, utilization of a sanitizing agent and the use of a stub cut to minimize cankers on structural wood. Ten experiments were conducted to evaluate the efficacy of methods to therapeutically remove fire blight cankers from apple trees with different age, vigor, training system and rootstock combinations in Washington, Oregon, Pennsylvania and New York, United States.
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