Years ago advise was to fill the void with concrete. Today, arborists
recommend keeping the void clean and a healthy tree will eventually
repair itself. Other than that, it may be worth having an arborist
take a look at it. You can call your local cooperative extension.

I had a damaged sycamore tree and a damaged hickory tree, both with
large holes in the base. The sycamore healed over and it sealed
itself. I treated the hickory hole using anti-fungicide because mold
was growing in the hole. Another year ants were taking up residence
in the hole so I used insecticides that year. But after 8 years the
hickory healed over and is doing remarkably well. It is over 50 feet
high and produces nuts every fall.

On Sat, 09 Oct 2004 12:10:25 -0400, Danny
wrote:

Hi,
I have a tree in the yard that's very large and close to the house. It's
still living and a viable tree. I have many very large trees close to
the house that could fall on the house if left long enough or if they
were to be ravaged by disease.

snip

Thanks for your help,

Danny