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Bleeding Cankers on Tree Trunks

June 14, 2007

The U of I Plant Clinic occasionally fields questions about oozing areas on tree trunks. These bleeding cankers are wet-looking, sometimes with watery or sappy material slowing oozing from the cankers. Often the cambium is dead in the cankered area. Bleeding cankers in trees are usually associated with a Phytophthora species (a fungal-like organism). In those cases, the inner bark and cambium are affected. Oozing cankers might also result from bacterial wetwood, insect injury (borers or surface-feeding), or other types of mechanical injury to the trunk.

Many tree species may host bleeding cankers caused by Phytophthora. Among these are apple, beech, oak, willows, maples, honeylocust, elm, and cottonwoods. The image shows bleeding cankers on red maple.

Most bleeding cankers appear on the lower trunk and usually begin in bark crevices. In Nevada, a Phytophthora-caused bleeding canker problem on silver maples produced cankers as high as 8 feet above the soil line. In some cases, the cankers continue to spread in the trunk. Still, bleeding cankers do not always kill the tree and may appear for only one year. The tree may seal off or callous over the affected areas. Phytophthora is thought to live in the soil. It may spread in water, in soil, on plant material, or on tools. Although it is unknown exactly how the bleeding cankers are initiated, wounds are known to allow entry of the fungus. Most organisms involved in canker formation cannot directly infect the bark and cambium. They need to enter wounds, injuries, or weakened areas.

Suspect bleeding cankers are easily spotted on the trunk. Removing the bark from these oozing cankers reveals wood beneath that is dead and darker in color than healthy, surrounding tissue. To confirm the presence of Phytophthora, submit a piece of the canker face (bark and underlying wood) to a diagnostic lab. Put the piece in plastic to keep it from drying out before cultures can be prepared from this tissue.

We do not have an effective management scheme for bleeding cankers. Chemical applications are not effective. Additionally, cutting out the cankered areas usually makes the situation worse by causing more wounds to the tree. Cankers often occur on trees weakened or stressed by environmental or site factors. It is probably best to do nothing to the affected area and to concentrate efforts on sound horticultural practices to improve tree health. These include removing dead branches, watering in periods of extended drought, and fertilizing with a balanced fertilizer in early spring or fall.

Bacterial wetwood may look much like bleeding cankers. Refer to Report on Plant Disease, no. 656, "Bacterial Wetwood and Slime Flux of Landscape Trees" (Adobe PDF), for more information on this look-alike disease. Bacterial wetwood causes liquid to ooze from branch crotches and wounds in the trunk. That disease is caused by bacteria that colonize the wood of the tree, ferment internally, and force liquid to ooze from branch crotches or weak areas on the trunk. Bacterial wetwood stays with the tree for life. The center of the tree eventually decays, but the process may take many years.

The most serious bleeding canker is caused by Phytophthora ramorum. The disease, known as sudden oak death, Ramorum blight, or P. ramorum decline, has not yet been found in Illinois. It is present in California, Oregon, and Washington and has been shipped to other parts of the United States on susceptible shrubs. If you see oozing cankers on trees and suspect this disease, call the Plant Clinic at (217)333-0519. You will be asked to identify the host, the nearby shrubs, and symptoms on both. It might be helpful to see pictures of the bleeding cankers. Ramorum blight bleeding cankers may start low in the tree but may be found as high as 60 feet aboveground. They are not usually associated with cracks in the bark. Crown dieback and death will be present. Ramorum blight kills shrubs and trees. Refer to Home, Yard, and Garden Pest News, issues 1 and 15, 2006, for more about this disease. A poster developed at Purdue shows infected plants (Adobe PDF).

Author: Nancy Pataky

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