Bacteria that overwintered in holdover cankers begin to multiply and invade nearby shoots or water sprouts. Shoot blight caused by reactivating cankers in the spring is known as canker blight. Later in the season the bark often cracks around the margins of the canker. Reddish brown streaks may be seen in the cambium under the bark of diseased branches. Pear orchard heavily damaged by fire blightĬankers appear as slightly darker, water soaked areas in the wood, which may produce amber coloured bacterial ooze that runs down the bark. Note browning of leaves and shepherd's crook and at end of shoot.ĭroplets of amber coloured bacterial ooze on fire blight-affected pear shootįire blight-infected apple fruitlet, with bacterial ooze Note blackening of pedicels (flower stems) In susceptible hosts or young trees the disease may travel rapidly down branches causing girdling and death of the branches or sometimes the main trunk.īlossom blight on pear. When shoots attached to scaffold limbs or trunks are attacked, the pathogen may spread into the structural wood causing cankers. Blighted leaves may remain attached to the tree throughout the winter. During warm and humid or rainy weather drops of milky to amber coloured bacterial ooze frequently appear on the blighted shoots and fruit. Infected shoots (or "strikes") wilt rapidly, and often form a shepherd's crook at their tips. Fruitlets quickly turn brown to black and eventually shrivel up.īlighted pear shoots are black in colour, while infected apple shoots are usually a lighter shade of brown. Young fruitlets are also very susceptible and appear water soaked and slightly off-colour soon after infection. Blighted blossoms appear wilted, shriveled and brown. Fire blight symptoms may appear on the blossoms, shoots, branches, trunk and rootstock.
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