Question
In the early spring I noticed what looked like sawdust coming out of a hole on a 4 year old columnar apple tree.  Just today I noticed that that small hole is now a large gash, and it extends into the trunk of this small tree about an inch above and below the gash.  I realize I should have acted when I saw the sawdust, but can anything be done now to save the tree?  The trunk is only about 2-3 inches around and this damage appears to have extended halfway into that.  Can the tree be saved?  What can I do to protect my other apple trees?  Should I put the poor tree out of its misery?

Thanks for your help.

Answer
I recommend you spray the trunk where the damage appears with an insecticide for borers (the latest is on called Onyx), Check with your local Garden type store for an insecticide for borers and follow the instructions. Here is a web link that will give you further information. http://www.ipm.uiuc.edu/hyg/insects/flat_headed_apple_tree_borer/