#116 The Emerald Ash Borer
December 18, 2008
Learning to identify trees is the business of the amateur naturalist — and these days, one that includes learning about and spreading the word about invasive pests that are threatening whole species, such as the Emerald Ash Borer.
Last weekend I took a short walk along the scrubby and thinly buffered banks of the Rivanna near Free Bridge with some fellow Master Naturalists. We were out to hone our tree identification skills – best done, I’ve found, after the fall of leaves when one is forced to use the most reliable tools of branching, bark, and leaf scar shape to confirm the ID.
Land disturbance and compaction at this site along the river has been pretty much uninterrupted with a succession of fords and bridges dating back to the 1700s – making the area vulnerable to a host of invasive species, such as Siberian elm, callery pear, and Oriental bittersweet. But we also found plenty of natives: box elders, sycamores, and green and white ash. I’ve learned over the short time I’ve practiced my naturalist skills that it is best to focus on one or two species in any given walk, lest I become overwhelmed and loose everything in the resulting confusion. On this day, I’d chosen the ash tree, genus Fraxinus, a tree whose wood is strong and straight-grained for use in hardwood flooring, but tough and elastic when used in baseball bats, canoe paddles, and oars.
Within several hundred yards I met both the green ash, common here in the southeast, and the white ash, at the lower end of its hardiness zone. Fraxinus belongs to that small category of trees and shrubs whose branching is opposite, and the mature bark presents interlacing ridges that form a diamond shaped pattern — both attributes helpful in the identification of a tree commonly planted for shade. And there, in the bottom-land along the river, we weren’t surprised to see it had taken root, because it thrives in moist soil while tolerating drought well.
As I paused to look closely at the pointy terminal bud of the green ash and compare it with the more oblique bud of the white, someone mentioned the Emerald ash borer, a bug that, as it name implies, is up to no good with a tree that fills out the hardwood canopy of our oak-hickory forests here in the south.
Later, perusing the various web-sites devoted to trees and forest health, I learned enough to alarm me – that the Emerald ash borer, a small, strikingly green insect arrived from Asian and made itself first known in Michigan in 2002. After claiming the lives of at least 30 million trees in Michigan alone, it has moved east, into Maryland and now Northern Virginia, where it was found in 2003 – eradicated – and then rediscovered in the summer of 2008 in Fairfax.
The emerald ash borer works fast, excavating serpentine tunnels through the circulatory system of the tree just below the bark. The effects are hard to detect in trees until the damage is done – upper branches die first, and as the canopy declines, the tree sprouts wildly at its base in the effort to make new leaves. The beetle’s range is about a half a mile, so destruction of ash trees in a radius around the infested site is one control method – as are quarantines of wood products and plant stock.
In July, the Virginia Department of Agriculture and Consumer Services established a quarantine area that consists of Fairfax, Arlington, Prince William, Fauquier and Loudoun counties and the cities of Alexandria, Fairfax, Manassas and Manassas Park.
Public awareness campaigns have sprouted up, too. Slogans such as, “Spread the word, not the pest” may help – and you can find more information at websites such as dontmovefirewood.org and stopthebeetle.info.
It is not an exaggeration to say that the loss of these trees may change our Eastern forests as radically as the chestnut blight altered them in the early 1900s.
At a time when “Buy Local” is being promoted for food purchases to Christmas shopping, here’s another to add to your list: buy your firewood locally and don’t transport it across county or state lines.
