Close examination will sometimes reveal a dark line at the edge of the canker. A slightly sunken, darkened canker forms in the invaded wood. The bacteria then move farther into and girdle branches and the trunk. Succulent plant parts are blackened and killed. Hail damage and pruning cuts also opens tissue to infection. The nectaries and other flower parts, hydathodes and stomates on leaves, and small wounds on succulent twigs and branches all can be sites of initial infection.
The bacterium is carried from infected tissue or from liquid oozing from the infected tissue to natural openings or wounds in by flower-visiting insects, rain, wind, birds, and various crawling insects. In some trees, the bacteria kill a portion of the branch and then stop development and do not seem to kill more of the branch. If conditions are wet, a cream-colored liquid may ooze out of the cankers and run down the trunk and branches in the spring. The affected twigs and branches may bend over into the shape of shepherd's crook and the blackened flower parts remain attached to the tree. If the branch is examined carefully, you will find the dead flowers where the bacteria first entered. The symptoms of fire blight include the rapid killing of branch tips and leaders, especially during flowering.
#Plum tree fire blight free
Note that the bacteria do not survive free in the soil. The bacteria build up on the plant hairs, stigmas, and other flower parts. In the spring, the bacteria are dispersed by insects, rain, wind, and animals. The bacterium over winters on infected plants in darkened, slightly sunken cankers. This bacterium can attack more than 75 species of trees and shrubs in the rose family of plants including apple, pear, quince, mountain ash, crabapple, hawthorn, cotoneaster, serviceberry, and pyracantha.
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