Question
We have a old hackberry tree, it has always appeared to be healthy, until this year.  We noticed the bark on the lower part of the truck started to split and it has gotten worse over several months. Now the bark is pulling away from tree, we noticed powdery areas where it looks like something is eating the bark and the bark just pulls away.  If you pull pieces of the bark off you see tiny little black ant looking things crawling on the tree trunk under the bark. It appears like it is boring into the trunk.  I can't seem to find out anything that this may be.  I don't want to lose this tree as it is our only tree, and it is beautiful.  HELP

Answer
Sounds like a decay fungi. Heart rot in living trees is caused by fungi which have the ability to decay wood. These fungi gain entrance to the wood of the tree through wounds, branch stubs, etc., which expose the bare wood. The fruiting bodies, mushrooms or "conks," are common on trunks of decaying trees. Production of fruiting bodies on a living tree is a sign of extensive decay in the stem at that point. A useful rule of thumb might be that a cubic foot of wood has been decayed for each conk produced. Heart rot fungi do not invade living wood of healthy trees. As long as the tree is growing vigorously the rot will be confined to a small central core of the trunk and the structural integrity of the tree will be maintained.

The ants and other insects are using the decayed wood as an easy place to build nests or live. IF the foliage is good --green and full_ the tree is ok. Decay fungi will slowly spread up the trunk and could cause the tree to become hollow. This not necessarily a bad thing. Hollow trees can live for many many years. IF an upper large branch breaks off and the end of the branch near the trunk  is hollow--this would mean the decay has spread up into the crown and the tree is in danger of possibly breaking off. Until this happens the tree is safe.

I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb of fertilizer per inch of trunk diameter scarred around the tree and watered in good. Apply just before a rain storm and you will not need to water. This will help increase the overall health of the tree.