Today, the trend is to plant higher density orchards with more valuable cultivars (many of which are highly susceptible to fire blight), making it difficult to avoid the disease all together. How do I avoid problems with fire blight in the future? Such a program should include diligent pruning to remove cankers in the winter, pruning during the growing season the removal of blight symptoms as they appear, a balanced nutrition program and the use of prediction models to determine appropriate timing for the application of control products to limit the spread of the disease. There is no cure for fire blight, but the spread of bacteria can be limited by using sound pest management strategies in an integrated management program. How do I save my trees once they are infected with fire blight? Blossom infections often result in shoot infections later in the season. Rainfall, high relative humidity and/or dew allow the bacteria to travel into the stigma of flowers and into the tree. Bacteria are spread to blossoms by insects (for example flies, honeybees) and splashing rain. In the spring, the bacteria can multiply very quickly, causing the surfaces of cankers to ooze bacteria. Where does fire blight come from?įire blight bacteria overwinter in cankers or strikes on host trees. Infections can also be identified by the discharge of bacterial ooze from infected plant surfaces. Cankers are typically smooth edged when first formed, but the margins become cracked and more pronounced with time. Cankers (Figures 5, 6 and 7) form once fire blight progresses into larger branches, trunk and the rootstock. Shoot blight (Figures 3 and 4) is characterized by the typical 'shepherd's crook' symptom. Blossom blight (Figures 1 and 2) results in blackened/shrivelled blossom clusters. The symptoms of fire blight depend on the part of the part of the tree that is attacked. Trees may need to be removed and replanted or, in severe cases, whole blocks of trees may need to be replaced. Economic losses to fire blight occur due to a loss of fruit-bearing surface and tree mortality. The severity of disease is dependant on cultivar and rootstock susceptibility, general tree health, cultural practices and environmental conditions. In severe cases, when the bacteria progresses into the trunk or infects the rootstock, entire trees can be killed. The disease can result in the loss of branches and tree structure. Fire blight, caused by Erwinia amylovora, is a bacterial disease of apple, pear, hawthorn, crabapple and ornamentals in the Rosaceae family.
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