Aug. 15 2019 03:48 PM

The newest invasive pest to jump ship from Asia is being found in landscapes all over Illinois, startling landscapers and worrying soil scientists.

Jumping worm
Photo: Wisconsin Department of Natural Resources

Meet the latest invasive species plaguing landscapes, the jumping worm. Like many troublemakers, it goes by several aliases: crazy worm, snake worm or Alabama jumper. According to a story in the Chicago Tribune, whatever you call these things, they’re all over Chicago and in other parts of Illinois and Wisconsin too. While they may be entertaining to watch, they are devastating for turf, plants, trees and soil.

Chris Evans, a University of Illinois Extension Service forester tracking the invasion told the reporter, “We consider anywhere in the Chicago area covered.”

Illinois has already taken hits from the emerald ash borer and the Asian carp. This latest invader is underfoot in city parks and bedeviling gardeners and landscapers.

A native of East Asia, jumping worms are recognizable by their white or light-colored collar or clitellum and their characteristic jumping or thrashing behavior. If disturbed, they thrash violently and sort of leap around a bit like someone who’s had way too many visits to Starbucks. “We get calls from some people who think they’ve seen a small snake,” Evans says in the story.

The article states that the Midwest has no native earthworms due to the glaciers that formed the Great Plains. All the earthworms in the region are imported European species, brought in to aerate soil and do other helpful things for it.

These guys aren’t helpful at all, and like bad house guests, they are eating machines. That’s the main problem with them. Mulch is their favorite food.

“Not all earthworms are created equal when it comes to helping soil and gardens,” Brad Herrick, a University of Wisconsin ecologist who studies the worms, is quoted in the story as saying. “There are definitely worms that are beneficial for gardens and have been around a long time, but the difference is that the beneficial ones are the ones that work vertically in the soil, creating pore spaces and mixing the soil.”

Jumping worms prefer the upper layer or surface of soil. They can be found in the leaf litter, mulch and top layer of organic matter where they munch away.

“They are voracious in their feeding behaviors,” Herrick says in the story. He says that some landscapers have reported having to reapply mulch multiple times within one growing season because the worms consume it so quickly. “They will stay in that top layer just consuming the organic matter until it’s all gone. Which is why you can see them so easily, and they’re kind of shocking in high abundance.”

This rapid depletion of the organic top layer of soil has a negative impact on plants. “Plants need that layer in order to germinate,” Herrick told the reporter, “and trees need it in order to survive.” In place of decaying leaves and other organic matter in the soil, large populations of jumping worms leave behind loose, granular soil resembling coffee grounds that lacks nutrients and easily erodes. This soil also no longer has the same moisture-retention qualities, so water passes through too quickly.

As a result, Herrick is quoted as saying, “nothing will grow in that patch of soil now. There’s nothing to hold the roots because it’s so porous and so loose. Even turf grass, under a high abundance of these worms, people can just pull up their grass like a carpet.”

Scientists’ worries about the worms’ eating habits extend much further than people’s yards. In other states, jumping worm populations have impacted native forests. “One of the big concerns,” Herrick says in the story, “is what can they do to a mature, healthy forest?”

The jumping worm invasion is considered relatively new in the Midwest. They were first officially spotted in 2013, at the University of Wisconsin arboretum in Madison. Researchers are still trying to predict their impact on natural areas. “We have seen some places where native plants are having trouble,” says Evans in the article. Prairie natives, adapted to the Midwest’s heavy clay soils, may suffer in soil structure that the worms have altered.

What can be done about them? Rolling back this invasion is unlikely, Evans is quoted as saying. “We confirmed them in 2015, in Northeastern Illinois,” he says. “We were surprised at the numbers, and at this point they seem to have spread all across the state.”

Part of the problem is that the jumping worms reproduce asexually. Their eggs are deposited in hard, dark cases resembling crumbs of soil making them nearly impossible to spot.

Even though the adult worms die with the first frost, the egg cases overwinter in soil or organic matter, ready to hatch out in the spring. No one knows exactly how they got to the U.S., but they probably have spread via potted nursery plants and in compost and mulch.

Once settled into “a place with lots of organic matter where the moisture level is right, they stick around and stick around,” says Herrick in the story. They can produce multiple generations in one Chicago summer, and are at their peak of maturity in August and September.

The worms are often larger than other earthworms and are recognizable by the distinctive pale or white collar that extends around their bodies and of course, their thrashing motions. If you spot any, Herrick suggests securing them in a plastic zip bag and placing the bag in the sun for an hour or so, which will kill them.

That’s not a permanent fix, of course; the eggs will still hatch in the spring. Researchers are searching for the right control strategy.

They’re looking to golf course managers for pointers. “Golf course managers hate earthworms,” Herrick says in the story, “because they leave little mounds that mess up their greens.” He recommends an organic fertilizer called Early Bird that’s a favorite of golf course greenskeepers for its earthworm-killing prowess.

Evans told the reporter that in the presence of this menace, soil care efforts must be ramped up. “Know that the fertility of your soil is going to be impacted if you have these worms, and so you’ll need to add compost and organic matter to the soil more often.”

But what about jumping worm egg cases that might be in that compost or mulch? Herrick’s research group recently published a study showing that heat exposure above 104 degrees Fahrenheit kills the egg cases, and commercial compost producers in Illinois and most other states are required to heat their products beyond that point.

“In theory those products should be OK,” Herrick is quoted as saying, “but you can’t know whether a forklift was contaminated with eggs when it lifted up that load of compost, or if someone had eggs on their shoes and contaminated it. You can’t know what happens between the compost pile and the store.” Mulch, their prime food source, is also a prime suspect when it comes to spreading their eggs around.

As a defensive strategy, Herrick recommends taking whatever brand of mulch or compost you use and dumping it into a bucket outdoors for a couple of weeks before using it. “Wait to see whether worms start to hatch, or worms that are already in the product show up,” he says in the story. If no worms appear, he suggests sticking with that brand.

This approach may work for small quantities, but what about the larger amounts that landscape contractors buy? The story did not address that concern.

Evans and Herrick also urge gardeners to avoid moving soil or mulch around to other yards, to slow the spread of the worms. But the story states that in Chicago, that effort may be in vain. In Central Illinois, Evans is still accepting reports of worm sightings as his research continues to track the spread of the jumping worm in the state. But in the Chicago area, he’s had so many reports that he’s no longer encouraging reporting.

“Once you have them in your soil,” Evans says in the story, “they’re going to be pretty hard to get rid of. They’re here to stay, and we just have to learn how to live with them.”

Let’s hope that some management solution is found before the worms jump beyond the Midwest.