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Cause of your diseased beech trees

By Al Cooke, Extension Agent
Posted Saturday, October 25, 2008

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Pittsboro, NC - Our house along the Haw River is surrounded by large Beech trees. They seem to be diseased with a fungus and/or insect parasite. Both yellowish and black “blobs” have appeared on the lower branches, and there are some branches that have developed a whitish infestation-looking coating. The trees are literally “raining down” some substance that is milky white and sticky when it gets on our cars - and leaves dark waxy spots on the driveway as well on the plants below.

Do we have Beech Bark Disease? Is anyone else dealing with this? We’re getting very concerned that we may loose our Beeches or have to cut them down to protect others.

With thanks for your time and advice.

Diane Pettus

Your description is consistent with a beech specimen that someone else brought to me recently. I narrowed that one down to either “wooly beech leaf aphid” or “beech blight aphid.” A standard reference from Cornell suggests of one of these aphids that “Beech trees in the United States seem capable of maintaining huge populations of this aphid year after year with little observable tree injury.” They are just some more of those creatures with whom we share our world.

Aphids (and a variety of other insects including scales and whitefly) process more plant sugars than their systems can digest. Consequently much of it is excreted in a form referred to as honeydew. The honeydew also serves as a substrate for sooty mold, which looks like a coating of soot. Sooty mold is a fungus that only causes problems for the plant in its interference with photosynthesis. But it thrives just as well on the honeydew that falls on cars or lawn furniture.

If the problem is sufficiently annoying, a strong blast of water from a water hose is often sufficient to remove most aphids. You probably won’t be able to reach the top of the tree.

Finally, verbal descriptions are often not sufficient for accurate identification and diagnosis. It’s always a better idea to bring in a specimen.

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