The borer was confirmed in Peoria and Tazewell counties last summer. I have looked at trees with Elizabeth Burns from USDA/APHIS a few times this summer, including one in Canton. The Canton tree did not have the borer, but we do suspect it is there somewhere.
To determine if a tree has been attacked, University of Illinois Extension horticulture educator Martha Smith suggests the following steps.
First, identify the tree. Emerald Ash Borer attacks only members of the Fraxinus genus, or true ash. On true ashes, buds, leaves, and branches form directly opposite one another on the twig or branch. If they do not, the tree is not a true ash and the EAB cannot attack it. The most common types of ash in Illinois are green, white, blue, black, and pumpkin ash. Some names are misleading -- for example, mountain ash is not a true ash. It is a member of the Sorbus genus and cannot be attacked by EAB.
Second, start to look for signs of decline, starting in the upper third of the tree canopy. If the tree looks unhealthy, look for D-shaped holes about the size of a BB. Anything round or larger has not been caused by EAB.
If bark on the trunk is splitting, lift it and look underneath. Snake-like tunneling under the bark may indicate the presence of EAB. Young sprout growth clustered at the base of the tree may also indicate EAB.
University of Illinois Extension has a handy checklist that can be used for identifying the tree and determining if EAB is present. The checklist, informational videos, and more information on managing this pest is available at http://web.extension.illinois.edu/eab.
If you suspect that your ash tree is infested with the Emerald Ash Borer (EAB) go to www.illinoiseab.com.