Friday, July 22, 2011

Beetles battle loosestrife

I took this photo a few years back, at Ottawa National Wildlife Refuge on the shores of Lake Erie. This marsh was being overrun by a beautiful but dastardly invader, purple loosestrife, Lythrum salicaria. The plant's magenta spikes of flowers are quite attractive, and unfortunately is still all too often sold by nurseries. Purple loosestrife has been here for a long time; it was originally brought to North America from its native Europe for use as a medicinal herb. It probably first jumped the garden wall nearly 200 years ago, but has really run wild the last couple of decades, at least in the Great Lakes, and can thoroughly overrun high quality wetlands. The resultant loss of biodiversity is profound.

Photo: John Pogacnik

On the good news side, I recently got an email and some photos from John Pogacnik, a biologist with Lake Metroparks in northeast Ohio. John's organization manages lots of wetlands, and loosestrife has made its way into some of them, and plenty of other coastal Lake Erie wetlands that John routinely visits.

So I was interested to hear of John's observations on recent infestations of "loosestrife beetles" in the genus Galerucella, such as in the above photo. There are two species of Galerucella used for loosestrife control, and I believe this one is the black-margined loosestrife beetle, G. calmariensis. The other is G. pusilla, and both are indigenous to the native range of purple loosestrife and are natural predators of the plant. The beetles were brought to North America in the early 1990's in an effort to combat the plant.

Photo: John Pogacnik

Both adult beetles and their larvae, which look like caterpillars, consume loosestrife. And they are gluttons for the stuff. John took these photos in wetlands at Conneaut Harbor in Ashtabula County, a famous birding locale. The last time that I was there, there were massive head-high dense stands of loosestrife in places. Well, apparently the hard-working beetles are laying waste to the stuff.

Photo: John Pogacnik

A pack of beetles works over a loosestrife plant. Go get 'em, boys! Apparently these beetles have spread from other introductions, and were not known to be intentionally released at Conneaut. The bugs have had localized successes in the western Lake Erie marshes, too.

Photo: John Pogacnik

That's a nice photo. An almost completely denuded clump of loosestrife, having suffered the wrath of the Galerucella beetles. So far, the beetles have shown no signs of jumping ship, and attacking native plants such as the beautiful, diminutive native winged loosestrife, Lythrum alatum. Hopefully that'll remain the case. All too often, these sorts of biological control schemes go utterly haywire, such as with House Sparrows and the Asian multicolored lady beetle.

With luck, the loosestrife beetles will knock this vegetative invader back far and wide, and keep it in check. But the long-term prognosis remains to be seen. John's photos certainly offer hope, though.


Wren nests in... said...

Seems like good news. But one can't help but wonder what will appear on the beetle's menu if/when there is no longer a smorgasbord of loosestrife.

Such a battle, as ably demonstrated by numerous historic examples, certainly illustrates conservation's dilemma--how to "correct" a "mistake" without causing another--and hints at the eternal environmental paradox: the strength of the interconnectedness of it all can be its greatest weakness. You can't tweak one thing without affecting something else...

Jim McCormac said...

Couldn't agree more, Wren. We people have a habit of making messes of things, and then compounding problems when we try to "fix" the situation.