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Sunday, October 6, 2013
Q: When driving on Interstate 81 from Christiansburg to Roanoke, I noticed a very welcome sight — a lot of the invasive ailanthus trees on the woods’ edge were dead. Is the highway department killing them? If so, I would be interested to hear how.
Chris Thompson, Floyd
A: It’s funny how many questions I get from people who want to know about invasive species. In the last few months alone we’ve dealt with stinkbugs and starlings, and now it’s the ironically named “tree of heaven.”
Like the stinkbug, it’s an Asian import. In ancient Chinese medical texts it was said to be a cure for mental illness and baldness, so I’m kind of surprised we don’t see ads for it on the NBC Nightly News. Even the name ailanthus sounds a lot like Cialis or some other wonder drug with a long list of whispered side effects. “You owe it to your loved ones. Isn’t it time you tried Ailanthus?”
Wikipedia says it arrived here in the 1780s, hailed as a “beautiful garden specimen.” But its beauty was eventually overshadowed by its ability to grow in places that had been clear-cut or disturbed by digging. It is apparently one of the first things to grow in Afghanistan after battles leave rubble behind. It re-sprouts quickly when cut, so getting rid of it can require some drastic measures.
Jason Bond, communications manager for the Virginia Department of Transportation office in Salem, dug into the history of the tree of heaven along I-81. He said that they intrude on culverts and can wreck their alignment, causing leaks and erosion.
Despite many people’s agreement with poet Joyce Kilmer, VDOT thinks there is such a thing as an ugly tree. A 2004 What’s On Your Mind column resulted from complaints that VDOT cut down a stand of trees in the median between mile markers 124 and 128. As the trees grew back, the department adapted their tactics.
According to Bond, two years ago, VDOT sprayed individual paradise trees on I-81 between Botetourt and Pulaski counties with what is known as dormant basal treatment. This is done in the late fall and throughout the winter seasons when the trees are dormant to penetrate the bark and spreads throughout the plant. This results in the death of the tree the following year.
Basal treatment is a very target-specific, hands-on method of treating unwanted trees and brush. The applicator (using a backpack) walks up to each tree and treats the base of the stem between 15 and 24 inches up, depending on the size of the stem. It’s clearly a lot of work.
It seems that cutting and spraying might not be the only ways to get rid of these heavenly scrub trees. Researchers at Virginia Tech have been studying a naturally occurring phenomenon that also seems to be causing problems for the trees.
Scott Salom in the department of entomology at Virginia Tech says that a fungus called nonalfalfae is a naturally occurring disease that kills the trees. It was first identified by Penn State researchers around Carlisle, Pa., in 2002. Tech researchers have confirmed its presence along northbound I-81 at mile marker 125, so it’s possible that the die-off you are seeing is the result of nature, not man.
The fungus seems to live only in higher elevations in Virginia, and while Salom says it has great potential for use as a biocontrol agent, it’s still a bit early to say for sure, and research continues. In the meantime, you can follow the progress of the disease on trips up Christiansburg Mountain. With the frequency of backups on that stretch of 81, there may be plenty of opportunity to look for trees of heaven as you climb.
If you’ve been wondering about something, call “What’s on Your Mind?” at 777-6476 or send an email to firstname.lastname@example.org. Don’t forget to provide your full name, its proper spelling and your hometown.
Look for Tom Landon’s column on Mondays. Visit the blog at blogs.roanoke.com/whatsonyourmind/.
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