Quite often I am asked, “When should I start treating my ash tree for Emerald Ash Borer?”
This usually starts a very good discussion with me as I believe that any good Certified Arborist should help educate their client about any concerns they may have. As it relates to the Emerald Ash Borer, it is important to establish the “15 Mile Rule.” If the Emerald Ash Borer has been confirmed within 15 miles of your location, you should be concerned and should develop a plan to save your ash trees. If your trees are outside of this “15 Mile Radius,” I believe that insecticide treatment is probably premature.
To determine where the Emerald Ash Borer has been confirmed in your area, look at the Agriculture Department website in your state for what they may have posted. If you are in Illinois, the Illinois Department of Agriculture has a very detailed list of confirmed Emerald Ash Borer locations. Here is the link to find out how close the insect is to you. They have it sorted by alphabetically by County. As of this last winter, there were approximately 195 cities with confirmed locations with Emerald Ash Borer up from just a handful in 2006.