Question
My lemon tree -type unknown the root stock grew but not the graft has developed some dead branches. It i like they are rotting They break off and inside have little burrows and dust. Ants are living on it It is a branchy tree and constantly produces heaps of lemons. It is about 20 years old

Answer
Hi Carolyn, It is probably a rough lemon which they used as root stock years ago.  It is hard to say what years of life the tree has as each root stock is different.  To cure the problem of the ants which are eating the tree, you could use Neem Oil which does not wash off or another type of oil spray that would be available at your local store.  The other types of oil spray you would have to re-apply as they do wash off.  Spray the tree and the ground all around your tree.  Cut off the dead branches.  I also have a feeling you may not be watering your tree as this is also a sign that the area is very dry to make a nice home for those critters.  So watering and spraying may keep your tree alive for many more years providing the root stock has a longer life.  kathy