Watch for Jumping Worms

August 13th, 2024

   Earthworms have long been a gardener’s friend – aerating the soil with their tunneling, decomposing organic matter, and leaving behind nutritious “castings” in the process.

Note the light-colored band that goes the whole way around the abdomen of this jumping worm.
Credit: Cornell University

   But there’s a new worm in town, and this one is as destructive to the soil as good ol’ earthworms are helpful.

   The newcomer is commonly known as the “jumping worm,” an Asian species that gets its name from its distinctively hyperactive, thrashing habit.

   If you’re out there digging this summer and notice worms that seem to be agitated and writhing, you likely have jumping worms.

   Mid to late summer is when they’re most active.

   Unlike our “normal” European-native earthworms that calmly squiggle and benefit the soil, jumping worms are fidgety, ravenous feeders that deplete the soil of organic matter and nutrition.

   They’re really not all that new to America, though, since they apparently first arrived on American shores in the late 1800s from Korea, China, and Japan. However, it’s only been the last five years that jumping worms have become a noticeable problem in Pennsylvania.

   The state Department of Agriculture’s Invasive Species Council has now classified jumping worms as an “emerging threat,” while the state Department of Conservation and Natural Resources reports sightings of this soil destroyer throughout Pennsylvania.

   “If you poke them, pick them up, or dig them up, they flail all about as a defense mechanism against predators,” says Penn State University entomologist Michael Skvarla in a Penn State Extension video on jumping worms. “They’ll flip all around. It’s very obvious once you’ve seen it.”

See the Wisconsin Department of Natural Resources video of jumping worms in action

   Jumping worms also are slightly larger than most European earthworms (four to six inches long), they’re darker in color (more gray than brown or tan), and they have a distinctive creamy-white band that completely encircles their bodies. European earthworms have a band, too, but it’s slightly raised and doesn’t go around the whole body.

   Also known as the “snake worm,” “Alabama jumper,” and “crazy worm,” jumping worms consume leaf litter at twice the rate of European worms, says Skvarla.

   That leads to the loss of soil’s protective cushion of decaying organic matter – opening forest floors and garden beds to bare spots, erosion, and weed invasion.

This soil texture that resembles coffee grounds is a sign of jumping-worm activity.
Credit: Nancy Knauss/Penn State Extension

   Instead of a soft, healthy “duff” layer, jumping worms leave behind a soil texture that resembles coffee grounds.

   What’s more, says Skvarla, jumping-worm castings (i.e. poop) are slow to break down, locking nutrients that otherwise would feed the soil. That change is disruptive to the nutrition needs of plants and other soil-borne organisms, Skvarla adds.

   Jumping worms grow and reproduce faster than European earthworm, allowing them to completely displace all other worms, according to researchers at the University of Massachusetts.

   Unlike European earthworms that tunnel underground in winter and typically live for three to four years, jumping worms are an annual species. Adults lay egg-containing cocoons that overwinter in soil, then begin hatching in April once soil temperatures reach 50 degrees.

   The adults die off in fall once temperatures drop below freezing.

   Jumping worms are asexual, meaning they don’t need a male and a female to mate. That means that even just one jumping worm that rides into a garden in a potted plant or in a load of topsoil is capable of igniting a new colony.

   What to do to head off jumping-worm trouble?

   Cornell, Massachusetts, Wisconsin, and Penn State Extension services offer these five bits of advice:

   1.) Inspect the pots of any new plants for jumping worms before planting them in the landscape. Bag and toss any jumping worms you find.

   2.) Inspect any bulk materials you buy (mulch, compost, topsoil, etc.) before spreading them. Ask suppliers if they’ve heat-treated the materials to a temperature of at least 130 degrees for at least three days. Otherwise, as a precaution, cover the pile with clear plastic for several days. Or stick with bagged materials.

   3.) Check your soil and compost for jumping worms, especially if you notice the coffee-grounds-like texture. The worms are usually close to the surface.

   Hand-pick, bag, and toss manageable populations. To drive jumping worms to the surface, drench the soil with a mustard solution of one-third cup of dry mustard (ground yellow mustard seed) in one gallon of water.

   4.) For larger outbreaks, solarize soil in late spring. This involves stretching a sheet of clear plastic over bare areas for at least two or three weeks, baking the soil and killing overwinter cocoons.

   5.) Do not buy or use jumping worms for fishing bait or vermicomposting. Avoid releasing any unused bait into the garden.