Fire blight crabapple11/26/2023 ![]() Canker extension may begin before, during or shortly after bloom, depending on the environmental conditions experienced during the spring in the orchard. Infections extend and spread into adjacent water sprouts, shoots and limbs resulting in canker blight. In the spring, renewed activity at the margins of cankers results in the extension of the cankers. In the winter, cankers usually dry up and become inactive. Bacteria are also easily spread from tree to tree on contaminated pruning tools. The bacteria in the ooze act as source of inoculum that is spread to other tissues or trees by visiting insects and splashing rain during wet periods. The ooze dries out and remains as a gummy substance or completely dries to an amber resin-like substance on canker surfaces where it remains for several months. ![]() At first, bacterial ooze appears a milky white drop but quickly becomes brown upon exposure to air. During rainy or very humid periods, bacteria ooze onto the surface of the cankers. The tissue under the bark initially appears water soaked, eventually with red streaks and finally turns brown. Eventually they become sunken with cracked margins (Figure 4-158). The cankers first appear brown to purple in colour. The cankers that form in the older wood girdle the branch, killing healthy wood from that point outward by cutting off the transport of nutrients and water. Fire blight progresses into the main limbs and trunk of the tree from infected spurs or shoots when warm temperatures with high humidity combine to form ideal conditions for fire blight. The most severe losses from both blossom and shoot blight occur when the disease progresses into older wood. The following is a description of trunk blight from OMAFRA’s website: Fire Blight According to The Ministry of Agriculture and Rural Affairs (OMAFRA) “Fire blight attacks many different parts of the tree, and fire blight symptoms are often referred to the part of the tree attacked – blossom, shoot, fruit, limb and trunk, and collar or rootstock blight.” Thank you for contacting the Toronto Master Gardeners about your ailing crabapple tree.Ĭrab apple is susceptible to a number of diseases which can harm the tree – Apple scab fungus ( Venturia inaequalis) and Fire blight bacteria ( Erwinia amylovora) are just two.įrom your photo it appears that your tree is covered in a black gummy substance which could be an indication of fire blight.
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