First came the killer bees. Then the murder hornets. Now scientists are expressing concern about an invasive species dubbed “crazy worms.”
Known also as Asian jumping worms, they have been detected in more than 30 U.S. states and can damage topsoil and leave little sustenance for plants and other animals.
Called “jumping” worms because of their violent wriggling when handled, they first appeared in 2013 at the University of Wisconsin-Madison Arboretum and have since spread across multiple regions in the U.S.
The worms, thought to have been brought to North America in the 19th century as fishing bait or in imported plants, have been spotted in Oregon, California, Missouri, Illinois, Iowa, Texas, Louisiana, Indiana, Minnesota, Kentucky, Tennessee, Maryland, Virginia and New York, among other states.
“These worms are known to change the soil structure, deplete available nutrients, damage plant roots, and alter water-holding capacity of the soil,” Nicole Flowers-Kimmerle, a horticulturist for University of Illinois Urbana-Champaign, wrote in a blog post this month. “This is especially a concern in our forests, where organic matter is limited. It is important to stop the spread of jumping worms.”
Also called “Alabama jumpers” and “snake worms,” the invasive species is native to eastern Asia. The worms can range in length from 4 to 8 inches and have a flat, milky white band called a clitellum that encircles the body, distinguishing it from other earthworms with pink raised bands, Ms. Flowers-Kimmerle said. The worms also can leap into the air and shed their tails to escape danger.
They can reproduce without mating. The worms lay eggs in the springtime that look like dark crumbs of soil, camouflaging with their surroundings. Although adult worms die with the first freeze, their eggs survive the winter protected in their cocoons, according to the Wisconsin Department of Natural Resources.
Jumping worms grow more rapidly, reproduce more quickly and consume more nutrients than other earthworms in the state, transforming soil into dry pellets that resemble discarded coffee grounds, the department says.
“Jumping worms consume organic matter such as leaves, mulch and compost. At high abundance, they have the ability to rapidly consume much of the organic layer that sits on top of the soil in forests. This organic layer is critical for plant and soil health because through natural decomposition, nutrients are put back into the soil,” said Brad Herrick, an ecologist for the UW-Madison Arboretum. “Also, the litter layer provides moisture and helps to keep soil from eroding. Without this litter layer, native plants have a hard time surviving and soil is easily eroded away and with it a lot of nutrients.
“So, generally with these effects, they have the ability to fundamentally change forest ecosystems,” Mr. Herrick said. “Maintaining a healthy, attractive garden may also be a challenge.”
All earthworms, including jumping worms, can harm forests by altering the soil structure and forest floor vegetation, says the Wisconsin Department of Natural Resources. Their feeding can lead to loss in soil moisture, exposed roots, erosion and an increase in pathogens and non-native plants, resulting in less diversity of native plants and animals.
The worms are often found in sugar maple forests and gardens that have been treated with wood mulch. They can even invade turf grass, Mr. Herrick said.
There are no viable ways to control jumping worms, Ms. Flowers-Kimmerle said. The best way to control them for now is to remove adult jumping worms to decrease the number of eggs hatched, she said.
To remove adult worms, she suggests placing them in a plastic bag, leaving them in the sun to die quickly and tossing them into the trash.
The horticulturist also recommends purchasing compost, mulch or other organic matter that has been heated to reduce the spread of pathogens, insects and weeds, and avoid purchasing jumping worms for bait or gardens.
Researchers are looking into other biocontrol measures for jumping worms. Mr. Herrick said using fire to manage a woodland or putting a clear plastic tarp over soil to heat it under direct sunlight for most of the day could help control the worms.