Unwelcome tree dwellers
Wisconsin's native trees are under attack by recent invaders to the state.
Friday, October 16, 2009 - 13:56
On a recent class trip to Madison's Picnic Point, my botany professor stopped our group beneath a tree to tell us a little about it. It was a green ash, he said, one of the trees typically found in southern Wisconsin forests. While we dutifully took notes about its ecology, he finished up his lecture with some sobering news. Take a good look at it, he said, because in a few years it would be gone.
My professor was referring to the recent onslaught of the emerald ash borer, an invasive insect native to Asia. This is just one invasive tree species that has made its way to Wisconsin in recent years. These species are not only environmentally damaging, but have economic impacts as well. For example, according to Madison's Office of the Mayor, ashes make up 30 percent of Madison's trees and would cost $6 million for the city to replace.
Emerald ash borer hitchhiked over to the U.S. as part of trade shipments, and eventually ended up in Wisconsin. Officials confirmed its presence in the state in August 2008 in the Village of Newberg, on the boundary between Ozaukee and Washington counties. Since then, it's been popping up in other counties, including Milwaukee, Kenosha, Vernon and Crawford. It hasn't yet been confirmed in Madison, but the ash tree on Picnic Point may only have a matter of time.
However, there may be some good news. A recent search of ash trees in susceptible counties using traps only turned up one adult emerald ash borer, which was found in Kenosha County. That's out of 279 traps checked in four counties, so the beetle doesn't seem to be spreading that rapidly. That gives areas that haven't been hit yet the opportunity to prepare. For example, the city of Milwaukee has begun treating its ashes with pesticides, while other communities are considering the removal of ashes to prevent the spread (read more at this link).
Emerald ash borer isn't the only problem that Wisconsin trees are facing. Just last month, officials announced the discovery of beech bark disease in Door County. This disease is caused by a combination of a fungus and an insect, neither of which are native to Wisconsin. While officials regard the emerald ash borer as a more serious threat, only five percent of beeches have natural defenses for this bark disease.
These diseases have prompted the Wisconsin DNR to enact measures such as the restriction of transport of firewood from certain areas to others. That is, if you're going camping in northern Wisconsin, it's much better for the environment to acquire firewood on site, rather than bringing your own. Even if the wood you're bringing isn't from one of the affected counties, it's still important to take precautions.
As for the ash on Picnic Point, it's hard to say what its future might be. But if it does eventually succumb to the emerald ash borer, it will unfortunately serve as yet another reminder of the need to stop the spread of invasive species.
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