Wilderness Underfoot: The emerald ash borer has arrived in Illinois

StoryImage( ‘/Images/Story//Auto-img-115212749432393.jpg’, ”, ‘This beetle is no jewel – The emerald ash borer, Agrilus planipennis, is about a half-inch long. It can be distinguished from green leafhoppers by its metallic color.’);
StoryImage( ‘/Images/Story//Auto-img-115212750932393.jpg’, ”, ‘The damage – Larvae of the emerald ash borer burrow under bark, into the sapwood.’);

Ash trees can be protected by keeping them healthy and watching for signs of infestation

Despite its tiny size and its attractive shimmering color, this emerald-green beetle is a feared pest. The emerald ash borer’s attacks on ash trees across the Midwest are predicted to cost billions of dollars in losses, and it has already caused the destruction of 20 million ash trees in Michigan alone.

This beetle is an invasive Asian insect that first appeared in Michigan in 2002. It may have been around for as long as a decade before it was spotted. June 13, the Illinois Department of Agriculture confirmed a siting of the beetle in Geneva, Ill. Forestry experts from local, state and federal agencies are now surveying ash trees in the region to determine the extent of infestation and to prevent the beetle’s spread.

As with many other beetles, the emerald ash beetle is a short-distance flyer. Its main route of infestation is through the transporting of ash nursery stock, logs, branches and firewood—and that’s probably the way it first reached North America. Because of this, in many states, carrying firewood across the state line and into parks for use in campfires is prohibited.

Early this spring, for example, the Wisconsin Department of Natural Resources passed emergency rules prohibiting the use of out-of-state firewood in state parks and any of its managed lands. Various restrictions are also in place in Michigan, Ohio and Indiana, where the beetle has already taken a toll on ash tree populations.

In the U.S., this beetle attacks only ash trees. The female deposits eggs, one at a time, in bark and crevices on the sunny side of the tree. She may lay up to 90 eggs. The eggs hatch about a week later, and wormlike larvae burrow into the bark to reach the underlying phloem (food-conducting tissues). Eventually, they attack sapwood, leaving curved tunnels reaching a foot in length. They winter over inside the tree, sometimes for two winters, and then emerge as adults.

As they exit the tree, the beetles leave D-shaped holes—this is one sign of infestation. Thinning or yellowing leaves may also be a sign of infestation. So is heavy damage by woodpeckers, which feed on the beetles. And, of course, look for the distinctive adult beetle itself, crawling about on the sunny side of the tree.

From the July 5-11, 2006, issue

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