![]() Twigs become tolerant to stomatal infections after they have stopped growing and become woody. ![]() Twigs and branches are also most susceptible during the same time period. Susceptibilityīuds appear to be most susceptible from when they are three quarters grown, until they open in the spring. Pruning and suckering young trees with unsterilized pruners will spread the disease. Trunk lesions develop from pruning wounds or migration of the bacteria from adjacent infected buds or shoots. It generally does not attack and kill branches that are more than 3 years old. It survives from one season to another in cankers and infected buds, surviving better in the large branch and trunk lesions than in the smaller twig lesions (less than 8 mm in diameter). The bacterial pathogen enters through open stomata (on leaves) and wounds on the plant. A sticky liquid containing many bacterial cells may ooze out of the lesions during periods of high humidity, and dead leaves will generally cling to the girdled trunks for some time.īranch dieback can occur on trees of any age. If you remove the bark at the crown with a knife, the tissue beneath is brown. These lesions can be difficult to detect, but close examination shows the bark to be slightly sunken and reddish-purple in colouration. Shoots emerging from buds generally become infected from infected bud scales.īacterial blight can cause lesions which encircle the trunk of young trees and cause them to die. Buds may be completely killed or only partially damaged. ![]() ![]() The outer bud scales are infected first and then the bacteria moves into the bud itself. Leaf buds and pistillate-flower bearing buds are also susceptible. The disease can also cause small, dark brown or black spots on the green nut, although this is quite rare. Leaves can develop small spots (usually less than 3 mm in diameter) that are reddish-brown and surrounded by a yellowish-green zone. Bacterial blight is easiest to detect during the spring. ![]()
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