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Unearthing a new enemy

Asian earthworms poised to invade the western Great Lakes region

The latest of invasive species in the Midwest — the Asian worm. The latest invasive species creeping it’s way into the Midwest — the Asian worm.

There’s a new ecosystem enemy on the loose and headed this way. Asian Jumping Worms are highly active, highly destructive earthworms that are often mistaken for Red Wiggler (Eisenia fetida) composting worms and accidentally let loose in compost piles.

NRRI Scientist Cindy Hale has spent the past 10 years studying and sharing information about the problems caused by the well-known European earthworms — nightcrawlers and angle worms, for instance. Now she’s sounding the alarm for the Asian variety, before they spread.

"The Asian species, their genus is Amynthas, are not well-established in the western Great Lakes region yet, but we’ve seen them in Wisconsin and in the Twin Cities metro area," said Hale. "And they’re poised to be coming this way. They’ve already become established in locations on the East Coast."

The Amynthas is often called Alabama Jumper or Jumping Worm and touted as being an excellent composting worm. They have a high metabolism and can live in very high densities. Amynthas can work through your kitchen and yard waste like nobody’s business. But if that compost goes into a garden, watch out — the voracious appetite of these earthworms can severely upset the nutrient system. In gardens out East where the Asian earthworm has invaded, Hale says, "it can get to the point of what we’ve started to call the ‘nothing grows here syndrome’."

We’re all familiar with European earthworms as fish bait and a gardener’s friend. But Hale’s research on their detrimental effect on native hardwood forests — especially the sensitive understory plants — has garnered quite a bit of attention over the past decade. And unfortunately, once earthworms establish themselves in an area, there’s really no effective way of removing them.

"We have to make people aware that all earthworms are exotic, so it’s technically illegal to knowingly introduce them into the state," Hale explained. "It’s just that people donít know a Red Wiggler from Amynthas."

Most vermicomposter’s don’t worry so much about European Red Wigglers that people order on the Internet for composting because they don’t survive Minnesota winters outside of a compost pile. But some species of Amynthas are tough and will survive freezing temps. The problem is that people don’t know when the wrong earthworms are in their compost.

"We recommend that outdoor composters use a traditional backyard pile that is turned and watered regularly," said Hale. "This activates the natural fungi and bacteria which heats the piles over 110 degrees, killing any earthworms or egg cocoons that may be in the pile." Compost barrels are also effective.

But people who want their compost in weeks instead of months have to be patient. It takes longer for the bacteria to break things down. Apartment dwellers might be even more tempted to use worms in compost because of lack of yard space. In that case, Hale recommends freezing any compost solid for at least a week or more before it is released outdoors. This will kill any worms and egg cocoons.

Hale and her team have compiled the largest database in the world on earthworms, and they’re always grateful for help. Volunteer citizen scientists are trained and equipped to help collect earthworm samples wherever they live and send them back for documentation. She’s also written a book, "Earthworms of the Great Lakes" (Kollath-Stensaas Publishing, Duluth, Minn.) that documents the impact of non-native earthworms, identifies the different species introduced here and give information about collecting earthworms for the database.

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