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Curbing spread of this eating machine should be top priority

July 20, 2012 12:10 am

SOME OF YOU will remember the plastic recumbent type tricycle for kids called The Green Machine. It was even cooler than the original Big Wheel--at least I thought so. That was probably because I didn't have one, making me green with envy. Speaking of green, have you heard about the Mean Green Tree-Eating Machine?

The emerald ash borer is on its way to a tree near you. It's a tree eating machine all right. The larva of this emerald green adult insect tunnels around inside an ash tree until it turns into an adult and crawls out of the wood to eat some leaves, have a family and repeat the process.

Alert readers will recall that this insect has been found in Virginia before. Emerald ash borers were discovered in Fairfax County in 2003. An eradication effort ensued and was presumed successful when the bug was not seen for several years. But it showed up again in Fairfax in 2008, at which point a quarantine restricted the movement of wood out of the Northern Virginia area.

Earlier this year, many of us were celebrating that the massive trapping effort (the purple triangle-shaped boxes hanging from trees along roadways) revealed no known spread of emerald ash borers outside of the known quarantine areas at the end of 2011.

Perhaps you've noticed the purple boxes hanging from trees. These are designed to attract adult emerald ash borer beetles to determine their presence. If the trap catches one, we know it is present. However, the converse is unfortunately not the case. An empty trap just means it didn't catch one. For several years, the traps didn't reveal a spread of the beetle, but now they have.

This exotic flat-headed borer has sprung up in nearly every corner of the state. In the past month emerald ash borer has been confirmed in Loudoun, Stafford, Caroline, Hanover, Prince Edward, Pittsylvania, Charlotte, Buchanan, Halifax, Mecklenburg, Giles and Lee counties.

The emerald ash borer is a -inch-long metallic green beetle native to eastern Asia. It hitched a ride to our shores in wooden packing crates and pallets from China and was discovered in Michigan 10 years ago. Since then it has spread into 15 states in the Northeast, Midwest, and mid-Atlantic, feasting on ash trees wherever it likes.

In early spring, adults climb to the crown of their chosen host trees and modestly nibble on the leaves--no problem, yet. By mid-summer, the adults mate and the female crawls down the trunk of the tree, laying 30 to 60 eggs (possibly up to 200) in bark crevasses as she goes. Within seven to 10 days the eggs hatch into small larvae, which burrow through the bark into the cambium and phloem tissue of the tree.

This is where the damage beings. The small larvae tunnel upward in the "inner bark" portion of the tree creating serpentine shaped tunnels that get bigger as the larvae grow.

For a tree, this is like cutting the jugular vein. The cambium and phloem are the living portion of the tree responsible for cell division and flow of sugars and nutrients. By late fall the larvae begin transformation into pupae and overwinter just beneath the bark. Each emerald ash borer pupa transforms into an adult in early spring and cuts a perfect "D" shaped emergence hole in the bark of the tree, and starts its climb.

Ash trees can be very valuable for timber, shade, wildlife, aesthetics and more. According to the Virginia Department of Forestry, the value of ash statewide is $170 million. Owners of forest land have very little recourse in saving ash trees within their stands, as methods for widespread treatment have yet to be developed.

Fortunately for most such land owners, ash trees are a small component of a typical hardwood forest in this part of the state. Homeowners, however, can pre-treat ash trees if they desire. In most cases, by the time damage is obvious to the casual observer, it's too late to treat the tree with the prospect of saving it. Most insecticides labeled for emerald ash borer purposes are restricted-use products requiring a license to apply.

Homeowners would be wise to give this decision careful consideration. Information about this and related issues is available at emeraldashborer.info.

Finally, if you have ash trees you suspect may be suffering from emerald ash borer, please contact your local Extension Office of Virginia Department of Forestry to identify and assess the damage. It's important to know where these beetles are to plan a counter attack wisely.

Lastly, the most important message with this and other tree pests is this: Don't move firewood! Check out this video for a compelling message: "A lot of mouths to feed," at hungrypests.com.




Adam Downing is an agent in Virginia Cooperative Extension's Madison County office, specializing in forestry and natural resources. Phone 540/948-6881; fax 540/948-6883; email adowning@vt.edu.




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