If emerald ash borers are widespread in your area, expect your trees to become infected in just a few years. It is therefore important to preserve them and treat them if they are infected. But how do you decide if your tree needs treatment? What you need to do is to have your tree inspected by a professional in order to determine if it can still be saved.
If removal of the tree is advised, then you should probably proceed to cutting it instead. Cutting it is evident of your tree has already lost a large chunk of its leaves, but if most of its canopy is still there, then you might still be able to save it. The next step is to evaluate the costs of treating along with the value of your tree. Do your feel that the price for the treatment is worth it? Does it have sentimental value?