The Emerald Ash Border (shown above) has spread throughout Hamilton and Clermont County Ohio. If this borer has invaded your Ash trees, you will find noticable D shaped holes in the tree trunk. In this case, the tree is infested and should be diagnosed.
"Proper arboricultural practices, such as proper mulch placement, watering to reduce drought stress, removal of dead or damaged limbs, preventing development of co-dominant leaders and avoiding soil compaction, will go a long way toward reducing infestation and damage from these wood-boring insects". by John C. Fech; Frederick P. Baxendale