We all like earthworms, right? OK, maybe not all of us. But they do have a lot going for them. They till and fertilize our garden soil. They make terrific bait for fishing — think night crawlers. They prop up the robin population. And they’re fascinating to watch.
But it turns out that earthworms aren’t all that admirable. To begin with, the common North American species is an invasive, introduced from Europe during the colonial period when no native worms existed here. Since their arrival, their propensity to rearrange soils has reshaped woodland habitats — worms are sometimes called “ecosystem engineers.” Still, North American forests have adjusted to the squirmy invader.
But there’s a new worm in town. And it’s a whole lot less welcome than the common earthworm. The Asian jumping worm, also known as the crazy snake worm, first showed up in the U.S. sometime in the 20th Century. Native to Japan and Korea, they laid low for decades. Then, about 10 years ago, their populations exploded. They’re now found in more than thirty states, including Maryland and Virginia. Chances are they’re in your garden.
Want to find out? Scoop up some soil and check out any worms you unearth. Are some longer than the common earthworm? Not as slimy? Much more wriggly? Have a look at the clitellum, the discolored band around the body. Is it close to the head, not raised, and completely encircling the worm? Those characteristics identify your worm as a jumper.
Asian jumping worms don’t really jump, but they do thrash around, sometimes so energetically that they flick off their tails trying to escape. Try holding one in your hand. Or not. At least they don’t bite. But they’re aggressive, prolific breeders, and hardy — they’ll survive a winter in frozen soil, under leaf litter or snow. They’re also voracious consumers of organic matter. And that’s the problem.
In your garden, in lawns, and in fields, these ravenous worms will quickly degrade the soil, leaving a gravel-like texture sometimes described as used coffee grounds. When they’ve polished off the soil litter, they’ll turn their appetite to shallow root systems. The result? The death of resident plants and farm crops, loss of nutrients, and soil desiccation and erosion. Jumping worms can devastate forests by consuming the roots of seedling trees. They’re particularly fond of juvenile maples. Vermont worries about the future of its maple syrup industry. Canada frets about damage to its northern forests.
What does this have to do with Chesapeake Bay? Soils degraded by jumping worms can erode, wash into streams, and end up in the Bay where they will increase sedimentation and reduce water clarity. Worse, the worms may incorporate heavy metals, passing along those toxic compounds to higher levels in the food chain — including in the Bay — where they will progressively bioaccumulate.
The rapid spread of Asian jumping worms suggests that they will be difficult to control. But we’re trying. Research programs are underway at universities and state agencies. Education initiatives are teaching people to recognize the worms, report their presence, and limit their rapid advance.
What can you do? Report any sightings and remove and destroy them. Never buy jumping worms for gardening, composting, or bait. Carefully examine your mulch to ensure the absence of worms and cocoons. Only buy mulch and compost that have been preheated to worm-killing temperatures. Be especially careful about potted plants and trees; in fact, a bare-rooted option is preferable, if feasible. Be cautious about moving plants on your property. Practice scrupulous garden hygiene by removing soil and debris from tools, equipment, and footgear, and washing clothes after gardening.
Above all, maintain perspective. New invasives pop up all the time and our initial reaction is to over-dramatize their threat. Jumping worms certainly aren’t welcome in your soil, but their presence should never discourage you from the joys of gardening.
Henry (“Hank”) Parker is a scientist and writer who previously lived in Annapolis but now lives in Vermont.
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