By Jim Lakin, MD, Master Gardener
My Uncle Casey was a farmer. He’d pick up a clod of dirt. Earth worms would slowly wriggle out. He’s say, “Good soil.” It’s almost become axiomatic that the presence of earthworms, mostly of the family Lumbricidae, indicates a healthy soil. Indeed worms consume leaf litter and organic material, release nutrients and help in soil aeration, altering soil structure. But they are not native. They, along with so much else, came over to North America in the 1600’s with early European settlement. For millennia the soil of our continent got along quite nicely without them.
In the late 19th Century a new genus, Amynthas spp or “jumping worms” arrived from East Asia on imported plants or other agricultural materials. They have made their way from the Northeast into the Midwest, first appearing in Minnesota and Wisconsin over the last 10 to 20 years. Unlike their relatively benign cousins, they have caused quite a lot of damage to the soils they have colonized. Like other invasive species, they take over. They invade the first 4 to 8 inches of soil muscling out other worms. Jumping worms consume both living and dead plant material at accelerated rates and change the soil to give it a “coffee grounds-like” texture, which can severely stunt or kill plants.
So how do you know if you have them? As their name implies, jumping worms are very active in comparison to other earthworms. They wriggle around vigorously. They also have a distinctive cream-colored band about a third of the way down their bodies. About the only other worm you might confuse them with is the night crawler. A really nifty app called iNaturalist can help in identification.
What do you do if you have them? Don’t despair. Some plants will succumb but others seem to tolerate jumping worms. You definitely want to remove and destroy any jumping worms you come across. Pop them in a resealable plastic bag and put them in the trash. Don’t spread them around your property. Carting infested soil from place to place should be avoided. They are annuals, laying eggs in leaf detritus in the fall, so be careful what you do with raked leaves. Above all, spread the word. You can report jumping worm infestations to the Great Lakes Early Detection Network (www.gledn.org). This is an organization which tracks invasive species around the Great Lakes and provides information to municipalities and individuals. If in doubt, report. They will verify. There’s a GLEDN app for either Apple or Google on which you can do this.
What can you do to reduce the chances of getting jumping worms in your garden? Be careful of any horticultural products you bring into the garden. Soils, mulch, compost, potted plants all are potential sources of the worms. If you are thinking about trying vermiculture, be very careful that you don’t buy misidentified worms. If you have a fisherman in the family make sure he disposes unused worms in a sealed bag in the trash, not in the lake or on the shore.
Want to learn more? Try this link to the University of Minnesota Extension.
At present there is no known means of eradicating jumping worms, so vigilance is essential!