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Chicago Master Gardener

A blog for Chicago Master Gardeners providing information on volunteer opportunities, training, workshops and resources.

Emerald Ash Borer Update

Posted by Ron Wolford -

The emerald ash borer has recently been found in Kane County, Evanston and Winnetka. The borer is about one-half inch long and appears brown in shade and under bright light is dark green in color. Millions of ash trees in Michigan have been devastated. This pest is a very serious threat to the 178 million ash trees in Illinois.

This is a very, very dangerous pest of ash trees," said James Appleby, a professor in the Department of Natural Resources and Environmental Sciences and a scientist with the Illinois Natural History Survey. "Ash trees in the state already are in a state of decline from other factors, so it is important that people look for symptoms of an emerald ash borer infestation, which represents an additional and real threat. If these borers are out there, we need to find them so we can take action to contain them."

The emerald ash borer, Agrilus planipennis, a native of eastern Asia, was identified in Michigan, as well as some areas of Ohio and Canada. Some counties in Michigan are under quarantine to prevent the transportation of ash trees, branches, logs and firewood. Millions of trees in Michigan have died or are dying from infestation. Scientists believe the insect has been present for as many as 10 years, possibly introduced in ash wood used in shipping, Appleby said. The accidental movement of infested firewood into Illinois could be the source of our current outbreaks.

The 178 million ash trees in Illinois represent about 9 percent of Illinois forestland. The total does not include trees in urban plantings or in nurseries. Drought, poor growing sites, lilac borers and native ash borers, and diseases, such as ash yellows, already are damaging many Illinois ash trees. All ash species are at risk from the new threat.

Signs of infestation, Appleby said, are D-shaped holes about one-eighth inch in diameter on large branches and trunks and numerous ash sprouts at the base of dead trees.

Adult emerald ash borers are commonly seen during sunny mid-summer days, feeding on leaves and crawling along branches and trunks of the trees. During June and July, they deposit eggs in the crevices of tree bark; about 10 days later, the larvae emerge and feed under the bark. Full-grown larvae, which are cream-colored and are about three-fourths of an inch long, spend the winter under the bark and in the sapwood.

Borer-infested trees may go undetected until symptoms such as upper tree canopy dieback occurs and the D-shaped emergence holes are seen on trunks and branches. Depending on tree size, symptoms may not show for a couple of years. In some trees a vertical bark split may occur on the trunk. If the bark is removed at such sites, S-shaped tunnels dug by the borer, known as serpentine larval galleries, can be exposed.

The emerald ash borer, Appleby said, easily can be confused with the brilliant green tiger beetle, a native insect often seen on the ground in open areas.

Source: Jim Barlow, University of Illinois News Bureau

Emerald Ash Borer Information

Illinois Department of Agriculture

USDA Forest Service

Information about Borer in Michigan, Ohio and Indiana

Photos of Adult Borer, Larvae and Damage

Emerald Ash Borer Life Cycle

How to Identify an Ash Tree

Other Ash Tree Problems

Emerald Ash Borer Education Group Video

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