The Emerald Ash Borer threatens U.S. ash trees

The Emerald Ash Borer threatens U.S. ash trees

by Ellen Goff

Stowaway bugs kill millions of plants. They pass through our nation's borders on ships and aircraft — unseen, silent and unnoticed. They settle in and begin to multiply, waiting for the day they'll be discovered. The saga of foreign insects has repeated itself many times over for more than a century, with similarly disastrous consequences.

Despite rigorous inspection efforts, alien species have arrived camouflaged among vegetation, enclosed in packing materials or buried in soil used as ballast in cargo ships. Without any known natural enemies, our indigenous plants and trees have low resistance to such foreign pests.

The Emerald Ash Borer (EAB), discovered in 2002 outside of Detroit, is the newest invader. Hidden away within wooden crates from Asia, EAB infestations spread through the region with the movement of nursery stock, hardwood lumber and firewood. Currently, there are outbreaks in Michigan, Ohio, Indiana, Illinois, Pennsylvania, Maryland and West Virginia.

According to the United States Department of Agriculture Forest Service, EAB is the worst tree-killing pest introduced into North America since the chestnut blight.

This latest plague is responsible for the death and decline of more than 25 million trees. One of the most frightening aspects of this scourge is that it attacks healthy, vigorous trees as well as stressed ones. The beetle lays its eggs on the tree's bark and when they hatch, the larvae tunnel into the tree. As the insects interrupt the flow of nutrients to the tree's crown and branches, dieback occurs. This process can continue for several years without detection, since the larvae exit holes are found high on the trunk.

Efforts to contain the pest in affected areas and prevent its further spread are ongoing. Illinois, Indiana, Ohio and the lower peninsula of Michigan are under federal quarantine to restrict the movement of host materials. "We believe that the EAB is a risk to all the ash in North America," says Sharon Lucik, spokesperson for the USDA. "EAB is spread typically by people transporting ash logs, firewood or nursery stock that might be infested. Campers might travel hundreds of miles, bringing the infected wood with them and unknowingly infest an area far from where they originated."

When an infestation is discovered, all ash within a certain distance — sometimes as much two miles away — must be cut down and removed. Eradication of infested and dying trees has cost millions in state funds so far, and much more will be needed before the disaster is under control.

If you live in an affected area and want to learn more, contact your state Department of Agriculture, state forester or county extension office. To find an arborist in your area, visit

Ellen Goff is a master gardener and environmental advocate. Aside from writing about and photographing plants, Ellen tends to a 3-acre landscape she shares with her husband, cat and border collie on the shores of Lake Wylie, S.C.

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