The Homeowners Column

The Homeowners Column

Flight of the green menace - Emerald Ash Borer

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator

The green menace has arrived. Unlike the dapperly masked cartoon character that saves the girl and fights villains, this green menace kills the tree and blights villages.

Emerald ash borer (EAB) alias the green menace was recently found in Rantoul and therefore, Champaign County will be under quarantine. In less than ten years this exotic pest has laid waste to millions of ash trees in several states and Canada. It brings a whole new meaning to a "pile of ashes".

Emerald ash borer adults are indeed emerald green 3/8 to 5/8 inch long beetles. Adult beetles are in flight between first of May into September, but are more abundant in June and July. Other beetles such as green tiger beetles can be green so accurate identification is important. The white larvae of EAB actually do the damage by feeding under the bark. Their feeding cuts off the tree's vascular system and therefore food and water. The adult beetles leave characteristic "D" shaped holes in the trunk or branches as they exit. However, in my experience on old ash trees with thick bark the "D" shaped holes are not always obvious until the bark is stripped.

The beetle flies short distances, but can survive for long periods and long distances as a hitchhiker in wood products such as wood packing crates from its native Asia. It probably entered into Illinois in infested firewood. As people picnic and camp this time of year remember to use only locally acquired firewood, do not store ash firewood for long periods, burn it before flight season starts in May and do not move firewood long distances.

At present EAB attacks only ash trees (Fraxinus spp.). If you have an ailing tree make sure the tree is really an ash. Ashes have compound leaves. Their leaves are composed of 5-9 (usually 7) leaflets along a main rib. Leaves are attached opposite each other on the stem. We have mainly green and white ash, but we also find European, black, and blue ash. Mountain Ash is a completely different beast, so it is not affected.

A sick ash tree may not necessarily be infested with emerald ash borer. Ash trees suffer from several other insect and disease problems including ash yellows, verticillium wilt, anthracnose, and other insect borers such as lilac/ash borer and apple tree borer. As with all trees practice good tree maintenance by applying 3-4 inches of wood chip mulch, watering during drought periods, and keeping weed trimmers and lawn mowers away from tree trunks. Healthy trees will survive attack longer than those in poorer health.

Quarantines and tree removals are helping to slow the spread of EAB. Pesticide treatments of imidacloprid and other professionally available pesticides are showing promise for tree protection and treatment. However treatment is not always the best option. Homeowners should weigh the value of the tree in the landscape against the cost of treatment and consider cost of the purchase and planting of replacement trees not susceptible to emerald ash borer.

Suddenly Japanese beetles don't seem so bad.

So you have an ash and are really confused about your options with EAB? Here are some helpful websites. or

If you suspect a tree has EAB, contact your local county U of I Extension office. Or stop by our office for fact sheets.

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