Gardeners around Maine are not ready to run up the white flag in the face of attacks by invasive jumping worms, but they are mounting a defense as the worm numbers increase statewide.
The Asian jumping worms have been in Maine for the last 100 years. For most of that time they were confined to a couple of locations in southern and central Maine. But their numbers have dramatically increased in recent years.
They are voracious, born pregnant and extremely difficult to kill. They also destroy the top layers of planting soils, forcing gardeners to change their planting strategies heading into the next growing season.
As the numbers of worms increase statewide and with no proven way to eradicate them, gardeners have to modify how and where they plant their vegetables and flowers. They are learning, along with the experts, how to do this and their limited options are showing some promise.
“Two years ago I knew I had jumping worms,” Jessica Seiders of Jefferson said. “Last year they really took hold [and] I was seeing them in every shovelful of soil.”
The worms are finding their way into gardens throughout the state, primarily in commercially purchased planting soil and compost that already harbors adult worms or their eggs.
Unlike earthworms — which are also an invasive species — the jumping worms do not slowly aerate and enrich the soil. Instead, they spend their time in the upper layer of soil where they rapidly consume organic material and churn the dirt until it looks like coffee grounds.
In the process, the jumping worms deplete the soil of nutrients, change its acidity level and dry it out, making it less suitable for growing things.
“They are now found statewide,” said Gary Fish, state horticulturist with the Maine Department of Agriculture, Conservation and Forestry. “This was a banner year for their reproduction,”
Cleaning out her gardens and preparing her garlic beds earlier this fall, Seiders said she discovered an infestation of the worms in both her raised beds and ground garden area.
“There were so many bunches of them tangled together, which were absolutely disgusting,” Seiders said. “I grew up on a farm [and] I’m a Maine woods girl, but these things freak me out.”
A major part of the freak-out factor is the behavior that gives the worms their names.
They are called jumping worms — or crazy worms — because they will thrash and writhe aggressively when disturbed.
There is ongoing research into how they could be managed, but so far the only thing that gives partial relief is heating any jumping worm-containing soil to 104 degrees Fahrenheit for a minimum of three days.
The process is called solarization and it only works by placing a clear plastic seal over raised garden beds or placing soil and compost in clear plastic bags, Fish said.
“The temperature will kill worms and cocoons,” Fish said. “The big ‘but’ is that it does not work on the ground because the worms will just flee the heat and there is always the chance of re-infestation.”
Given the sheer number of worms and the destruction they were causing in her garden area — including burrowing into growing carrots and potatoes — Seiders knew something had to be done.
Since there is no proven effective way to eradicate the worms, she is changing her entire gardening approach starting now.
“We have started this fall to get a head start,” Seiders said. “It’s a bit overwhelming so putting it off until spring makes it feel even worse.”
To start, Seider is pulling up any weed mats — ground cover that prohibits weeds where you don’t want them competing with vegetables or flowers — and will not put any additional mats down.
Turns out, the weed mats create the perfect jumping worm breeding environment because they provide just enough warmth to protect the eggs and larvae. The adult jumping worms did not survive the winter, even under the cover of mats.
It’s also a full court press against the jumping worms down at the Kennebec Estuary Land Trust in Bath where Becky Kolak, executive director of the trust, said they are taking action now to do what they can against a jumping worm infestation.
“They are in almost all of our garden beds,” Kolak said. “We researched and contacted the state horticulturist and came to the conclusion that there is no way to get rid of them, so we are now in the process of gardening with them.”
The trust maintains 42 raised garden beds as part of an edible educational gardening program. All of the produce and herbs grown there are donated to the local community through a gleaning group.
Following a recommendation from Fish, Kolak plans to implement solarization at the gardens next spring to hopefully kill off as many of the worm’s cocoons as possible before they mature into soil-destroying adults.
Seiders plans to exclusively use raised beds next spring and modify how she deploys weed mats.
“This way we can control the soil in the beds,” she said. “We will put the weed mats down so they won’t be sitting directly on the soil but will be sitting up on blocks.”
Because her compost pile is completely infested with the worms, Seiders will purchase compost she hopes is worm-free.
The Kennebec Estuary Land Trust takes great pains every year to make sure the soil is as perfectly conditioned as possible at the start of the growing season, Kolak said.
The jumping worms have undone much of that work, she said.
The best hope is that after a productive 2023, the jumping worms will experience a population collapse next year, Fish said, adding that has been the case in Vermont the past several years.
Reasons behind the drop in jumping worm numbers may be due to dry conditions or depletion of food the worms need to survive.
“I don’t think anyone knows definitively,” Fish said.
For now, he and gardeners around Maine are waiting for improved jumping worm eradication methods.
“There are no good management options for Asian jumping worms,” Fish said.
Correction: An earlier version of this report misstated the number of days that soil needs to be heated to 104 degrees Fahrenheit to manage the population of jumping worms.