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St. Paul, Minn. (February 17, 2004)—Do you think the big trees in your yard are the picture of health? You may want to take a closer look or ask a plant pathologist for his or her expert opinion.
According to Dr. Joseph G. O'Brien, plant pathologist with the USDA Forest Service, winter weather can be particularly stressful to trees. "Ice storms and heavy, wet snowfalls can increase the risk of breakage of tree stems and branches," O'Brien said. "In the worst case scenarios, tree failures cause costly property damage and power failures. Homeowners can avoid these expensive situations however, by inspecting their trees on a regular basis and taking corrective action," he said.
Plant pathologists with The American Phytopatholgoical Society (APS) recommend tree owners inspect their trees once or twice a year for the following possible defects:
Dead wood. Dead trees or branches should be removed as soon as practical. Dead branches and treetops that are broken and lodged in the crown of the tree (known by foresters as "widow makers") are especially hazardous.
Cracks. Cracks in trees are areas where the bark has been split, exposing the wood below. Cracks may be an indication that the tree or branch is failing. Cracks that extend deeply into a tree or branch, or are paired with other tree defects, can compromise a tree's structural integrity.
Weak branch unions. Branch junctions can be strong or weak; often the difference is in the angle of the branch attachment. Two large branches that come together at a very acute angle may become hazards if their point of attachment to the main stem is compromised.
Decay. Fungi that cause decay enter trees through wounds, so trees with large, open wounds should always be inspected carefully for the presence of decay. Decay usually proceeds in a tree from the center toward the outside. When wood is decayed or missing in the structural portions of the tree, the remaining shell of sound wood may not have sufficient strength to keep the tree from failing.
Cankers. Cankers can be identified by the "target" shape of the defect that they cause, or by either a sunken or raised appearance of the bark. Cankers are caused by fungi that kill the bark or outer woody portions of a tree, often with associated decay of the stem or branch behind the canker.
Root problems. Wounds caused by lawn mowers or weed whips can cause open wounds on roots, which can become infected by root rotting fungi. Diseases and injury to the structural roots of a tree can seriously compromise structural integrity.
The American Phytopathological Society (APS) is a nonprofit, professional scientific organization dedicated to the study and management of plant disease with 5,000 members worldwide.
