Even with all our technology and knowledge, Mother Nature often throws us a curve now and again. A few years ago it was the invasion of the Asian Long-Horned beetle which destroyed a number of trees in Chicago and surrounding suburbs, or the unusually warm fall when bulbs were coming up in December and just last week the invasion of thousands of gnats during a Cubs' game at Wrigley Field.

Now we may have to deal with a new potentially damaging insect, the Emerald Ash Borer. This insect is originally from China. It entered the United States on crates and pallets. It was found in six southeastern counties of Michigan last year and spread to Ohio and Windsor, Canada. Over five million ash trees have been infected. The borer attacks green, black and white ashes. Infestations cause severe dieback with the death of the tree possibly occurring within two years.

The adult Emerald Ash Borer is a metallic, coppery green, 1/2-inch-long beetle. Adults emerge in May. The adult female will lay 60 to 90 eggs during June and July on the bark or inside cracks and crevices of the tree. The eggs hatch in a week or so. Tiny white larvae burrow through the bark and create S-shaped tunnels, disrupting the water and nutrient conducting tissues of the tree. The larvae feed into the fall. Symptoms start with a yellowing of the leaves. Branches start to die from the top of the tree downward. Dieback will continue until the tree dies. The borer over winters in the larval stage and exits the tree as an adult beetle the following spring making 1/8-inch D-shaped holes.

In Michigan, the Department of Agriculture has quarantined all ash trees and ash wood products such as timber and firewood in affected counties. With this action it is hoped the spread of the beetle will be stopped. Another part of the plan to control the borer is to cut down and destroy every ash tree within a 1/2-mile radius of any infested trees before adults emerge and can fly away. Also every tree within a 1/2 to 3/4-mile radius from the infestation will be treated with imidacloprid to kill newly hatched larvae and adults during feeding and maturation.

If you find this beetle in Illinois, contact the Illinois Department of Agriculture or your local University of Illinois Extension office.

Source: Raymond A. Cloyd, University of Illinois Extension