Mainers reported drastically fewer invasive “crazy worms” disrupting their soil in 2024 after an apparent population explosion the year before.
Also known as Asian jumping worms or snake worms, they’ve been in Maine for more than a century but have been multiplying in recent years. Nearly impossible to stop, the fast-reproducing worms eat through organic matter in soil, making it harder to grow plants, and posing a big risk to the state’s valuable forests if they spread.
It’s possible the 2023 population boom was an outlier. But these worms are still somewhat of a scientific mystery, and it’s hard to say what that data could mean for future years, according to one plant scientist.
“It’s very difficult to understand what’s happening with these,” said state horticulturist Gary Fish. “I don’t know enough to provide a forecast.”
The state horticulture program collects reports of suspected sightings of the worms. In 2023, it received 361 submissions and confirmed 303 of them. In 2022 and 2024, confirmed submissions numbered fewer than 20.
It’s also possible the state reporting system was advertised more that year, Fish said, but the weather conditions were more suitable to worms too.
Existing research suggests the “cocoons” of eggs that the worms lay can stay dormant for years waiting for favorable conditions. It’s possible wet conditions in 2023 led many of them to hatch at once, Fish said.
Jumping worms have been found in all Maine counties except Aroostook, Piscataquis and Washington, and were recorded last year in five new towns across Hancock, Lincoln, Oxford and Penobscot counties.
“I really think our biggest concern is them getting into the forest, and that’s true for all worms,” Fish said.
Maine has no native earthworms, and even familiar species can disrupt forest health by reducing the soil nutrients, decomposition processes and moisture while increasing acidity and making it harder for native species to grow.
In home gardens, jumping worms may harm young seedlings by disrupting the young roots before they can get established. Newer research suggests that “solarization,” or covering the soil with a clear plastic seal that heats it, can kill worms and cocoons if the soil temperature reaches 104 degrees Fahrenheit.
In-ground, the adult worms can flee the solarization patch, but the method can work for containers of soil or compost.
Tilling soil between mid-May and mid-June, when the young worms are growing, may also kill some of them and mix their castings back into the soil, keeping nutrients from washing away. In established beds, try watering less and don’t add mulch so the conditions aren’t as good for worms.
Fish’s advice to landowners who find the worms: “First and foremost, not to panic. They are all around, and you’re not doing anything wrong, necessarily, if you have them.”
The horticulture program also urges anglers not to dump unused worms in the woods and people selling or sharing seedlings to wash soil off the roots before transporting them. When buying compost, look for ones that have been heat treated at 131 degrees Fahrenheit for three days.
