On 12/29/2011 2:54 PM, Matt wrote:
I have a couple of big silver maples, 40 years old and about three
feet in diameter.


I've noticed in the past few years that fox squirrels are trying to
dig a hole in each tree by clawing and biting. Each wound is in the
trunk, about chest high, where a small limb has been removed years ago
and the trunk is growing out around the stub. So there is already a
kind of recess in the trunk, and they are trying to turn it into a
hole. I have noticed that sometimes a lot of thin sap runs out of the
wound and wets the side of the trunk. Sometimes woodpeckers also do
their work on the same wound.


What is the best way to stop the damage and make the trees live longer?

They can't claw away healthy wood. They're removing rotting wood to
make a nest. It won't necessarily injure the tree - this is, after
all, how wild squirrels make their homes - but if a tree has several
such holes, you may want to have an arborist give you an evaluation of
the overall health of the tree.

Usually, once you get a hole in the trunk, you get decay starting in
it. It used to be advised to fill the hole with cement, but they've
found that doesn't stem the progress of the decay. Usually you can
keep the tree well-watered and healthy for several more years,
although if the decay eventually becomes substantial you'll have to
take it down. Like I said, ask an arborist for an opinion. Some cities
have arborists on staff; if your city does, you can probably get a
free consult.