Raise your hand if you are tired of hearing about new invasive species. I’m right there with you. Aside from the fact that there’s too much bad news around as it is, we’re still working on a cure for those good old-fashioned pests that rival the common cold in terms of eluding conquest. Japanese beetles, European chafers, buckthorn, wild parsnip, Japanese knotweed — enough already.
We don’t need a new invasive species every year, but try convincing them, right? I half-expect to get a bulletin one of these days on some tropical soil-shark that stowed away in a shipload of potting mix. Probably it’ll feed on moles and woodchucks, but will also burst up out of lawns to swallow small pets, and gardeners might lose a finger while weeding. That would kind of put lily-leaf beetles in perspective, wouldn’t it?
So I’d be a lot more hesitant to tell you about a new and significant threat to forests, landscapes, and gardens if it wasn’t for the fact that you can make a real difference in preventing its spread.
The new pest is Amynthas agrestis, a super-size (eight-inch long) earthworm known as the Asian jumping worm, Alabama (or Georgia) jumper, snake worm or crazy worm. It’s sold as bait, and unfortunately is also hawked as a substitute for the harmless red wiggler used in worm compost bins. Its name comes from the fact that it moves rapidly on top of the soil, resembling a snake more than a worm. Lively and strong, it can flip out of your hand. Assuming you want to touch it.
Other than its impressive squirm factor (in every sense), what’s the problem with Amynthas agrestis — worms are good for the soil, aren’t they? Not so, my friend; crazy worms are an exception. These are not your grandparents’ worms. OK, that didn’t come out quite right. Let me rephrase it.
Here in the Northeast where glaciers scrubbed our bedrock bare a few years back, we have no native earthworms. There is debate, especially in the forestry world, over just how much of a mixed blessing our European earthworm species are, but I won’t get into that. Let’s just assume earthworms are good.
A native of Japan and Korea, Amynthas agrestis is a very different animal. Their reproduction, for example. Other earthworms are hermaphroditic, that is, they possess both male and female organs, but they still need to go out on a date with another of the same kind. Crazy worms, however, are parthenogenic, which means they are all females who spew out cocoons teeming with baby female worms by the hundreds without needing to mate. Ever. All it takes is one to make an infestation.
They also mature twice as fast as European earthworms, completing two generations per season instead of just one. And their population density gets higher than other worms. And remember, they’re big.
That adds up to an unprecedented worm biomass that will essentially consume all organic matter. This includes your lawn and the roots of annuals, perennials, and shrubs. In the woods, crazy worms destroy native wildflowers, wiping out trillium, bloodroot, Jack-in-the-pulpit, ladyslipper, and other understory plants. Ground-nesting songbirds like the oven bird disappear.
When an Amynthas agrestis infestation removes organics from soil, it becomes clumpy and granular and prone to compaction and erosion. Forest soils actually subside, exposing tree roots. Wisconsin Department of Natural Resources invasive species specialist Bernie Williams stated bluntly, “Their introduction into our state poses a huge threat to the future of our forests.”
Amynthas agrestis can be distinguished from other worms by the band near their middle, called a clitellum. In most worms it’s thicker than the rest of their body. In crazy worms it’s even with their body, and is milky white to gray in contrast to their dark color. Size and behavior also set them apart.
Crazy worms are transplants, and that’s how they often spread. Whether in a potted plant from a garden center or a gift from a South Carolina relative, these monsters hitchhike long distances with transplants. They also move from infested areas, mostly in southern states, in shipments of mulch.
There are two ways of telling if your potted plant harbors dangerous fugitives. One is to turn it upside-down and gently remove the root ball. If crazy worms are present, some of the roots, as well as some potting soil, may be missing. The thing is, there may only be young worms present, or very few, so damage might not be evident.
A better solution is a mustard solution. Mix a gallon of water with one-third cup of ground yellow mustard seed and pour this slowly into the soil. It won’t hurt the plant, but worms (even “good” ones) will come to the surface and you can check for miscreants.
Because of their acrobatics, crazy worms are valued as fishing bait. This is illegal in most places, but it does happen. To be safe, anglers should securely cover bait containers and destroy all unused bait by placing it on bare concrete and crushing it. If you have a household worm bin, only use European red wigglers, Eisenia fetida, which won’t survive outdoors over the winter.
With a presence in Wisconsin and Minnesota, Amynthas agrestis is hardy to USDA Zone 4 and possibly colder. Right now there are at least five known crazy worm infestations in Warren County, N.Y., and it is likely there are plenty more throughout northern New York State.
If you suspect you may have found crazy worms, please call your local Cornell Cooperative Extension office or New York State Department of Environmental Conservation office.
If you think it’s an invasive soil shark, though, I don’t want to know about it.
Paul Hetzler is a horticulture and natural resources educator with Cornell Cooperative Extension of St. Lawrence County.