Written By Tom Pavlesich.

Posted on June 27th, 2016.

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As beech trees die from beech bark disease (caused by a fungus and an invasive insect), the resprouts can choke out tree seedlings and other plants, reducing diversity in your woods.

This blog is dedicated to Squeak. She called the other week confused after attending a workshop. A forester at the workshop had talked about killing beech trees because they’re bad for our woods. The forester mentioned “beech bark disease,” but to the best of Squeak’s memory, beech has been around for a very long time. Growing up she knew it to be a valuable tree. She remembered beech from her youth that were so large they could be hugged by a couple of grown-ups at once. What changed?

The answer all comes down to beech bark disease. It’s a complex condition caused by an invasive aphid-like insect called a scale and a fungus common in our woods. The scale insect was introduced to North America at the turn of the 20th century. It sucks the juices out of beech trees while hiding under a coat of cottony white wax. Like little dentists, they first numb a small area of bark before inserting their straw-like mouthparts. Just like you can’t feel the dentist working on your tooth after an injection of Novocain, the beech tree can’t feel the scale insect at work, leaving the tree defenseless.


Invasive scale insects feed on a beech tree while covered by a white cottony wax.

If it was only the scale insect, our beech trees would probably be fine. But a fungus common to our woods takes advantage of the small area numbed by the scale. The fungus infests this open wound, killing healthy tissue. Add up the wounds from many scale insects, and the resulting fungal infections become a huge problem for beech. Eventually the tree dies.


Fungus infecting a wound created by a scale insect on American beech.

The reason the forester said beech are bad has to do with what happens as the big beech trees die. In response to injury, beech has the remarkable ability to sprout hundreds of new trees from its roots. Normally this would be a great way to replace a dead tree, but these smaller trees are clones of the larger one, with all its strengths and weaknesses. That means the sprouts are just as vulnerable to beech bark disease. As a result, a vicious cycle begins. The root system of a larger tree sprouts hundreds of smaller trees, which get infected, die from beech bark disease, and send up their own clones to start the cycle anew. Each time this cycle repeats, the patch of sprouting beech grows larger, preventing other types of tree seedlings from growing. Just like the number of scale insects and fungal infections grow to kill a beech, the beeches affected by beech bark disease can grow to do harm to the woods.


As large beech (background) die from beech bark disease, the re-sprouts (foreground) can choke out tree seedlings and other plants, reducing diversity in your woods.

Beech bark disease isn’t going away, so we have to learn to live with it. Beyond recognizing it, there’s not much you as a woodlot owner can do. If you’re cutting firewood or planning a timber harvest, though, here are a few things you or your forester may want to consider:

  • Avoid using heavy equipment and ATV’s around dead and dying Beech. Running over the roots can stimulate even more root sprouts than normal.
  • Not all beech trees are bad! Leave beech with little or no sign of the scale insect. In particular keep any beech that have smooth bark, because they have fewer places where the scale insect can survive.
  • When cutting beech, focus on removing those with rough bark or that are heavily infected by the scale insect. To limit sprouting, cut the tree in the summer, when more of the tree’s resources are in the tree itself rather than in the roots.
  • To further reduce resprouting, or if your woods are overrun by beech, your only option may be to use herbicide. This is a complicated decision, so take time to learn more about proper methods and precautions to protect the environment.

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