How to prevent invasive jumping worms from ruining your garden
As home gardeners are cleaning up their spring flower beds and vegetable patches, they might notice signs of a relatively new invasive species that’s made its way across Pennsylvania. Though Asian jumping worms (Amynthas agrestis) aren’t that well known yet, the damage they cause could last for years.
About seven years ago, Nancy Knauss first spotted them in her yard in Pittsburgh. They didn’t look like common European earthworms.
“They just writhe around and jump and I’m thinking, ‘there’s so many of them, these are different,’ ” Knauss said.
Knauss is the statewide master gardener coordinator for Penn State Extension, so she knows her worms. These were large, behaved like snakes, and were close to the surface. She admitted to being a little creeped out by them.
Knauss did a little research and discovered that the invasive species could cause headaches for gardeners.
“The jumping worms actually degrade the soil,” Knauss said. “Your soil texture will change. It’s very granular, and people often compare it to coffee grounds.”
She said adult worms can eat anywhere from two to three times their body weight in soil every day. Those coffee grounds are the castings the worms excrete. When it rains, the castings and the nutrients they contain are washed away too quickly for surrounding plants to soak them up. The soil can become depleted of nutrients.
Knauss said bare soil left by the worms could lead to other invasive species in gardens, like Japanese knotweed and stiltgrass. She said researchers are looking into how degraded soil from jumping worms could impact the germination of maple seedlings, which rely on that upper layer of soil. The worms can even damage turfgrass.
How to spot them
- Large worms that move around like snakes
- A mass of worms near the surface
- Soil appears granular, like coffee grounds
- The light-colored clitellum, or reproductive band around the jumping worm, wraps around its body. In European earthworms, this band is reddish-brown and doesn’t wrap entirely around the worm
How to avoid them
Adult jumping worms are annual, dying off in the winter. The cocoons overwinter in the soil. In April, when temperatures consistently reach 50 degrees F, they hatch.
“They are so fertile so they don’t need a partner to produce cocoons,” Knauss said. “So one adult worm can produce up to 60 cocoons. Each cocoon can have one to two eggs. She said the cocoons are tiny, like mustard seeds.
- When buying plants at a sale or trading with neighbors, wash the plants of garden soil. Buy or trade plants bare-rooted or repot in a sterile potting medium.
- Jumping worm cocoons are also in mulch. Purchase mulch from a reputable producer and make sure it’s been heated to 130 degrees F for at least 3 days.
What to do if you get them
- To kill cocoons in soil, try solarization. In late spring or early summer, when temperatures are higher, wet the area where you know you have the jumping worms, then cover it with clear polyethylene. Let that heat up for two to three weeks until the soil temperature exceeds 104 degrees Fahrenheit for at least three days.
- To kill adult jumping worms, handpick them from the soil, place them in a plastic bag in the sun, then throw them in the trash.
- A mustard solution can irritate the jumping worms and help bring them to the surface for picking. Dissolve one-third cup of dry mustard in one gallon of water and drench the area where you have worms.
- An organic fertilizer made of tea meal and commonly used on golf courses can be used to kill jumping worms. Apply it in April or May to kill newly hatched worms and again in the summer.
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