Friday, December 7, 2007

The Emerald Ash Borer

As if we didn't already have our hands full with invasive species in MN, another one might soon be crossing our borders. The emerald ash borer has already killed more than 20 million trees in Michigan, Ohio, and Indiana, and has made it as far west as Illinois. Wisconsin and Minnesota are next in line, and we also happen to have the most ash trees of all the states in the country - more than 1 billion ash trees in the two states combined! Minnesota alone has about 870 million ash trees.

The adult ash borers eat the leaves of the tree, but they aren't the real problem, and only cause minimal damage. The real buggers are the larvae, which feed off the inner bark and disrupt the tree's ability to transport water and nutrients. By the time you see the adults, the damage has already been done.

Because of the numbers of trees already killed and the great threat posed, the USDA has imposed quarantines and fines on moving wood from infested trees. MN and WI state parks have banned out-of-state firewood in an attempt to prevent the transport of the beetles into the states. The insects are not strong flyers and can only make it about a half mile on their own, but humans tend to give them a lift - 80% of the infestations in Michigan, for example, were traced back to firewood.

Entomologists say the arrival of the emerald ash borer in MN is inevitable, and all species of ash appear to be susceptible. The loss of the ash tree would have a significant impact on our urban landscape (my backyard would be a completely different and much less appealing place!), but it would have an even more detrimental effect on our forests. In the river gorge, green ash is a common tree species, and prickley ash and black ash are also present.

For more information:
Photos:, David Cappaert, H. Russel, Michigan State University,1607,7-153-10370_12141-69866--,00.html, Steven J. Baskauf

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