Beavers can be trouble for trees

November 20, 2009|By JEFF RUGG / Creators Syndicate

Q: We live on a lake and have never had a problem with beavers before, but one has attacked a 2.5-foot diameter ash tree on our property. It ate some of the bark down to the wood on two sides of the tree, leaving two sides untouched. What can we do to protect the tree and help it recover?

A: Beavers have been spreading across the country as rivers and streams have become cleaner. They don't always build a dam. When the young leave home and travel to new places, they first seek protection by burrowing into the bank. They can do a lot of damage by creating large holes in banks of levees and earthen dams. The damage may not be noticed on a retention or detention pond until rains fill it.

On large rivers, they don't build dams because of too much flow. They still can cause erosion damage because they burrow under shoreline tree roots, undermining the tree, which falls into the river ripping out more roots and soil.


Beavers usually attack small trees because the bark is thinner. The small tree falls over and more tasty small twigs are available to eat. It takes a lot of work to cut down a large tree to get to the small branches, and in the meantime there is nothing to eat. Your lake shore probably has few small trees to eat.

The first thing to do is wrap the trunk in wire mesh. The smaller the holes the better. Large holes can allow the beaver to get its teeth through and nibble. The fencing needs to be attached to stakes to hold it in place. Adult beavers often weigh 50 pounds but can weigh as much as 100 pounds. They can stand up over 2 feet high and pull the fencing down.

The first thing that needs to be done for the tree is to use a sharp knife and clean up the loose ends of the wounded bark. Then, wrap the tree in burlap or tree wrap paper for the winter to protect the wounded area from extreme temperature fluctuations. Take off the wrap in the spring, so that insects and decay organisms aren't able to hide behind it.

Don't spray the tree or paint it. These products harm the existing good cells that need to heal and also can hide decay organisms from view.

For the rest of us who don't have large animals eating our trees, we need to be on the lookout for the much more common damage caused by small critters like mice and voles. They eat the trunks of trees in the winter, but they are short, so the damage is going to be low to the ground. The damage might be hidden by mulch, leaves or ground cover vines. Keep these critters away from tree trunks. Mice eat young trees because the bark is thin; they especially like eating the bark of newly planted fruit trees. When they eat all the way around a tree trunk, the tree will die.

The best prevention is to install a wire barrier with small holes. It doesn't have to be quite as strong as before, since mice don't weigh quite as much as beavers. As the trees mature, the thicker bark helps prevent damage from small mammals.

The Herald-Mail Articles