Fireblight is a common and destructive disease of pear, apple, quince, hawthorn, firethorn and members of the rose family.
Fireblight is a disease caused the bacterium Erwinia amylovor. The most notable symptom of the infected trees is the dying back of branches, from the tips back.
The leaves start to wilt and turn black, hanging from the tree. As the name “fireblight” suggests, it looks as though the branches have been scorched.
The tip end of an infected branch often bends, giving it a hooked appearance. This is called a “shepherd’s hook.”
If you follow the branch back from the tip, you may notice a small sunken lesion in the limb. This is called a canker. This is where the bacteria overwinter.
They begin to rapidly multiply in early spring. A type of milky, sticky discharge may be noticed oozing from the cankers in wet weather. This discharge is dispersed through wind, rain and insects.
Insects can transfer the bacteria through the flowers of the plant, as can rain and wind. The bacteria can also spread via pruning tools.
Unfortunately, there is not a cure for infected trees and shrubs, but there are preventive steps to take.
• Bacterial growth slows later in the summer, when temperatures rise. At this time, pruning out infected limbs will slow the spread the following year.
• When pruning infected limbs, be sure and make the cut through healthy tissue. Follow the limb back to the canker and make the cut at least 6 to 12 inches beyond that.
• Disinfect the pruners after every cut. Rubbing alcohol is a good disinfectant.
• New, soft, succulent tissue is more susceptible to bacterial infection, so avoid fertilizing with excessive nitrogen.
• Remove any water sprouts from the plants. This is succulent growth that provides a pathway to the trunk of the tree.
• Antibiotics are available that may help with some control. These are sprayed when the plants are blooming. Once infections occurs, these sprays are ineffective.
• Planting trees that are resistant to fireblight is the best way to avoid the disease. A list of resistant plants as well as additional information on fireblight can be found at www.aces.edu. Search for “fireblight.”
Danielle Carroll is an extension agent for the Alabama Cooperative Extension System.