Ash tree holes
I do not see any specific borer holes. In the photos , there appears to be a wound with some decay in it. Anytime a tree is stressed, or there is a wound, insects, especially many different types of borers, are attracted to the tree and/or wound and can infest the tree. With most borers, the borer is a secondary issue and is present because there is a primary problem causing the tree to be stressed or to decline. If present (I cannot see specific borer holes in these photos), the type of borer would need to be identified to know the timing and type of treatment. (Perhaps call your local Extension office for more information). Treating for a native borer may help reduce stress on the tree; but depending on the primary reason the tree is stressed and therefore attracting borers in the first place, treating for borers may or may not save the tree. See the links for additional information on borers. Please let me know if you have more questions.
Borers and Bark Beetles: http://nfs.unl.edu/ash%20decline%20borers%20with%20EAB%20full%20sheet.pdf
Borers of Shade Trees:http://extensionpublications.unl.edu/assets/pdf/ec1580.pdf