Bacteria can then be spread very efficiently from blossom to blossom by honey bees. If weather conditions are warm and humid, the bacteria are able to multiply rapidly in the blossom nectar. This ooze, consisting of millions of bacterial cells, is easily transported to blossoms by insects such as flies, ants, and beetles. During spring and early summer, cankers that were not removed the previous season may reactivate and produce bacterial ooze, which may or may not be visible. Leaf discolouration in late summer caused by fire blight rootstock blightįire blight bacteria overwinter primarily in cankers on infected trees. Oozing bark may be observed near the base of the tree.įire blight rootstock blight. Trees may weaken and die beginning one to several months after planting. It is sometimes mistaken for crown rot due to brown discoloured tissue under the bark at the base of the tree. Rootstock blight may not exhibit typical fire blight symptoms.
Cankers may also expand to girdle limbs.įire blight may also spread into the root area, leading to tree death. Invaded shoots wilt and die, and may be mistaken for early shoot blight. 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. If the tree cannot be saved, contact a tree care service to remove it before it becomes unstable and falls down.Fire blight symptoms may appear on the blossoms, shoots, branches, trunk and rootstock. Prune during dry weather or during the winter to minimize the spread of the disease. Dead or dying branches should also be removed. In the case of infectious cankers, remove branches six to 12 inches below the canker. In periods of drought, water trees thoroughly. In winter, wrap young, thin-barked trees, such as maples and apples, to prevent sunscald and frost cracks. Keep trees healthy and prevent infection. The best defense against canker is prevention. They rarely kill established trees, but they may cause severe growth deformities.Ĭontrol: Most canker-causing fungi infect stressed or injured trees. The size of a canker can range from a small lesion on a branch to a massive dead area on the plant's trunk. Cankers are caused by everything from mechanical damage inflicted by a lawn mower to environmental stress such as frost cracks and sunscald, to types of fungi and bacteria.ĭamage: On young or smooth-barked trees, the surface of the canker is often discolored, and tissue around the canker is enlarged. Canker is a tree disease characterized by a localized dead area on a trunk or branch.
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