Emerald Ash Borer

2018 September 15
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I’ve been kind of expecting these to turn up sooner or later. We were up at the Eagle Harbor Sands on July 28, 2018 when a friend showed me this brilliant green beetle that had landed on his arm.


While I hadn’t seen one before in the flesh, I don’t think that there is much doubt that this is an Emerald Ash Borer, Agrilus planipennis.




If you live anywhere in the northeastern US, you’ve most likely heard of these. They are an invasive species from eastern Asia, and their larvae bore under the bark of the various species of ash trees. Once these beetles get established in an area, the native ash trees are usually pretty much wiped out within a decade. The ash trees back in their home range in Asia are resistant to them, but aside from demonstrating that resistance is possible, that doesn’t do our local trees much good.

There has been a lot of work done to track and attempt to slow the spread of these beetles, but that has overall been about as effective as attempts to halt other invasive pests. That is, it is mainly a delaying action putting off the inevitable. There are two main issues: one is that insects are hard to eradicate in general, there are just so many of them. And bark-boring insects like these are a particular problem, because they spend most of their lives hiding under bark where very few predators or diseases can get to them, and they are sheltered from pesticides. The other big issue is that, no matter how much you ask people not to haul around firewood to their campsites that might be infested with these beetles, people do it anyway.

The main hopes are that something will develop a taste for these beetles, and start eating them fast enough that they no longer threaten the trees; or that by delaying the spread of the beetles we can give the ash trees a chance to be selected for resistance before they are all destroyed. This could take a long time, though. And in the meantime, it is likely that ash trees will become very rare in North America, like what happened to the American Chestnuts and the Elms. Which will be a great shame.

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