The Homeowners Column

The Homeowners Column

Be on the Look out for Emerald Ash Borer

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator

It's time to watch your ash – your ash tree that is. An exotic insect pest called the emerald ash borer has killed millions of ash trees in Michigan, Indiana, Ohio, Maryland and Ontario Canada. That's quite an accomplishment considering the borer is no bigger than a penny. Last year emerald ash borer (EAB) was discovered in Illinois at ten sites in Kane County and six sites in northern Cook County. It was found last month in Skokie. Trees are removed and quarantines are in place to help slow the spread of the beetle. It brings a whole new meaning to the phrase a "pile of ashes".

We need the observant eyes of local homeowners and gardeners to keep EAB from spreading. Adult beetles could be seen now on tree trunks or feeding on leaves. They are generally more abundant in June and July. Emerald ash borer adults are emerald green 3/8 to 5/8 inch long bullet-shaped beetles. The white larvae actually do the most damage by feeding under the bark of trees. Their feeding cuts off the tree's vascular system and therefore food and water. The beetles leave characteristic "D" shaped holes when they exit the trunk or branches.

The ash story would be much worse if the insect had gone undetected and areas left without quarantine. Movement of ash trees, logs or firewood out of quarantine areas and states is prohibited unless it has been treated properly and is labeled with the USDA shield.

The adult beetle flies short distances but can survive for long periods and long distances as a hitchhiker in wood products. It may have made it into the U.S. in wood packing crates from its native Asia. Researchers speculate the insect came into Illinois in firewood from infested emerald ash borer areas.

As people picnic and camp this time of year they may be tempted to bring firewood with them. Or maybe they don't burn it all at the campsite so they bring it home. Bad idea and may even be illegal depending on locations. Emerald ash borer and all kinds of other nasties can hitchhike on firewood. Use only locally acquired firewood and leave any unused at the campsite. Try a random act of kindness and leave it for the next guy. Don't be a Typhoid Mary (or is it borer Bob?)

At present EAB attacks only ash trees. If you have an ailing tree and you suspect EAB, make sure the tree is really an ash. Ashes have compound leaves. That means their leaves are composed of 5-9 (usually 7) leaflets along a main rib. The leaves are attached opposite each other on the stem. We have mainly green and white ash, but we also find blue ash. Mountain Ash is a completely different beast, so it doesn't enter into this discussion.

A sick ash tree may not necessarily be infested with emerald ash borer. Here in Illinois 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. Keep trees healthy with proper 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.

If you suspect a tree has EAB, contact your local county U of I Extension office. Brochures are available at offices with helpful information about identification.

For more information on EAB, check the web site at

Garden Walk

University of Illinois Extension Champaign County Master Gardeners' Garden Walk isSaturday, June 23. Tickets are available at area garden centers and at our Extension office.

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