Raise your hand if you’re tired of hearing about new invasive species. I’m right there with you. Aside from the fact that there’s way too much bad news these days in general, we still can’t find good solutions for “old-fashioned” invasive species like Japanese beetles, European chafers, buckthorn, wild parsnip and Japanese knotweed.
We don’t need a new invasive species every year, but try convincing the invaders, right? I half-expect that one of these days we’ll get a tropical soil-shark that stowed away in a shipload of potting mix. Probably it’ll feed on moles and woodchucks, but will also burst out of lawns to swallow pets, and gardeners might lose a finger while weeding. That will sure put the lily-leaf beetle in perspective.
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 actually a coterie of Asian earthworms in the genera Amynthas and Metaphire. These super-size (20cm. long) earthworms are variously known as invasive jumping worms, Alabama jumpers, snake worms or crazy worms. Unfortunately, they can be sold as bait, and also hawked online as a substitute for red wigglers used in worm compost bins. They move rapidly on top of the soil, resembling snakes more than worms. Lively and strong, they can flip out of your hand. Assuming you want to touch them.
Other than their impressive squirm factor (in every sense), what’s the problem with invasive jumping worms – worms are good for the soil, aren’t they? Not so, I’m afraid; 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’s a debate, especially in the forestry world, over just how much of a mixed blessing European earthworm species are, but I won’t get into that. Let’s just pretend European earthworms do more good than harm.
Native to Japan and Korea, the jumping/ crazy/ snake worm is a very different animal. Take their reproduction, for example. Other earthworms are hermaphroditic – they have both male and female organs, but still need to go out on a date with a pal. Crazy worms, however, are parthenogenic, meaning they’re all females who spew out cocoons by the hundreds teeming with baby female worms without the fuss of needing to mate. All it takes is one to start an infestation.
They also mature twice as fast as European earthworms, completing two generations per season, potentially even three if autumn is longer than usual, instead of just one. And their population density is much higher than other worms. And remember, they’re big.
That adds up to a prodigious worm biomass that can essentially consume all soil organic matter. I mean everything: plant roots, leaf litter, mulch. In the woods, crazy worms degrade the soil to the point that trilliums, bloodroot, Jack-in-the-pulpit, ladyslipper and other understory plants die out. Ground-nesting songbirds like the oven bird and hermit thrush disappear as plant cover vanishes.
When crazy worms vacuum 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 states bluntly, “Their introduction into our state poses a huge threat to the future of our forests.”
Asian worms can be distinguished from other kinds by the band near their middles called a clitellum. In most worms it’s thicker than the rest of their body. In crazy worms it is flush with the body, and is milky-gray to white in contrast to their dark gray color.
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 visiting relative, these monsters hitchhike long distances with transplants. They also get moved from infested areas, mostly in southern states, in shipments of mulch.
There are ways to tell if your potted plant harbors dangerous fugitives. One is to turn it upside-down and gently remove the root ball. Crazy worms will leave a void in the potting media, and plant roots may be missing, too. Also, the soil will be clumpy.
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.
As of September 2014, it is illegal to possess crazy worms in NY State, but they are still occasionally sold as fishing bait because their acrobatics supposedly make them attractive to fish. To be safe, anglers should securely cover bait containers and destroy all unused live bait by placing it on 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 northern states like Wisconsin and Minnesota, jumping worms are hardy to USDA Zone 3 and possibly colder. Right now, there are at least five known crazy worm infestations in Warren County, NY and at least two in St. Lawrence County. It’s likely there are more yet to be discovered.
For some excellent information on crazy worms, visit dnr.wi.gov and search “Invasive earthworms.” If you suspect you may have found one, please call your local Cornell Cooperative Extension or New York State Department of Environmental Conservation office.
If you think you’ve caught a glimpse of an exotic soil-shark, though, I don’t want to know about it.
Paul Hetzler is an ISA Certified Arborist and former CCE educator. He now lives and teaches in Canada and writes weekly natural-history essays for newspapers, magazines, and Public Radio in the U.S. You can read more of his work by picking up a copy of his books Shady Characters and Head of the Class.