Saturday, July 9, 2011

Eradication Success Stories

Feral swine is one species the Oregon Invasive Species Council would like to add to the list of eradicated invasive species in the State of Oregon. Photo by Texas Department of Agriculture.
How many noxious weeds have been detected and then completely eradicated from Oregon? That question came up recently while I was traveling with Tim Butler, ODA’s Noxious Weed Program Manager. There are many examples of successful eradication on specific sites, but actually eliminating a weed from Oregon has been rare. We could think of only one example: Spartina alterniflora (saltmarsh cordgrass).

Maybe we can add mile-a-minute weed to that list. There is an old record from Portland that is thought to have been associated with soil used as ship ballast. This plant hasn’t been seen for over a century, so I think it is safe to say it is no longer established. Maybe someone plowed it or pulled it or turned some goats out on it, or maybe it just died out. We’ll never know, but it’s an easily noticable weed, so it wouldn’t surprize me if humans had a hand in it’s demise.

There are a number of other weeds that are being treated now with the goal of eventual eradication. If we keep after them, we might get rid of them once and for all: kudzu, Patterson’s curse, Alyssum murale, giant hogweed, African rue, distaff thistle, and purple starthistle. Some of these projects have been going on for more than a decade and have reduced known populations to just a few plants. You’d think it would be easy to finish them off—it’s not. You can kill all the plants and still not be done. Weed seeds stay viable in the soil for years and don’t germinate until conditions are right. A good example is kudzu. We thought we had successfully eradicated kudzu from three sites a couple of years ago (2 in Portland, 1 Aurora), but this year we found new plants at both of the Portland sites. Tim thinks they were seedlings. It is a good thing we went back and checked.

Our track record with invasive insects is somewhat better. Breeding populations of gypsy moths have been eradicated several dozen times since the first one was discovered in 1970. We’ve also had success against half a dozen Japanese beetle infestations in Oregon. One other notable victory was the eradication of an infestation of granulate ambrosia beetles from The Dalles in 2008. We’ve found and treated other potential invaders before they became established, but I can’t think of any other examples where we’ve eliminated breeding populations.

Overall, compiling examples of successful eradications results in a pretty short list. If there are other examples, I’d like to know about them. Can you think of any? Have we ever eradicated an invasive fish, mammal, bird, or other vertebrate from Oregon? It would be nice if we could add feral swine to the list someday. It should be possible—they may spread like weeds, but at least they don’t have a seed bank!

Dan Hilburn