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How to Handle Beech Bark Disease

Written by Bill Byl | Thursday, February 19, 2015

Yet another threat to West Michigan's forests and trees is emerging in our area. Beech bark disease results from the relationship between an insect (beech scale) and a combination of species of fungi. Beech scale is an insect that feeds on the sap from the inner bark of a tree's trunk and branches. Though the scales themselves don't threaten the health of the tree, after feeding they leave exposed areas where fungal colonization is more likely to occur. Beech scales are most easily detected by the "wool-like" white wax they excrete during feeding. In cases of heavy infestations, major portions of the bark and branches develop a "whitewashed" appearance.

The disease seems to be spreading south and west over time. It was most prevalent in Eastern Canada, Maine and New England during the 1960's; Pennsylvania and Ontario in the 1980's; and was first detected in Michigan's Upper Peninsula and northwestern Lower Peninsula in 2000. Recently, it's been found along the Lake Michigan shoreline and as far south as Allegan County in the southwestern portion of the state.

As with many fungal-related diseases, there is no known control for beech bark disease once a tree has contracted it. The best way to prevent an outbreak is to control the pest population that spreads it. Scale can be very difficult to control, as the species has a shell that protects it from insecticides that work through direct contact. Fortunately, there has been some success with multiple applications of dormant or horticultural oils to suffocate the scale, and through trunk or root zone injections of a specific insecticide. According to the Michigan Department Of Natural Resources, the state has lost approximately 2.5 million of its 32 million American beech trees to date... and the figure is expected to rise.

The wood from a beech tree becomes extremely brittle once it dies, and can pose a significant hazard if a target is nearby. When trees get to that point, the options for removing it are limited, as they're not stable enough to support either their own weight or the weight of arborists who would need to work on them. It's recommended that you have the trees inspected for scale activity and make a pest management or removal plan before they get to this stage.

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