'Crazy-snake' earthworms threaten VT forests

There is an unwelcome earthworm in our midst.

This comes as no surprise to folks with an aversion to slime.

But to gardeners and farmers who rightfully tout the contribution of most wrigglers to soil health, this is hard news indeed.

Bragging rights have been handed down for generations: Plots dotted with fertile worm excrement (castings); clods riddled with worm holes (where air and nutrients more easily migrate), and kitchen scraps reduced to compost (vermiculture).

Enter Amynthas agrestis.

It performs like a champ, confined to a bin. But the unchecked proliferation of this Asian exotic invokes decidedly stark landscapes, warns soils scientist Josef Görres, a professor at University of Vermont.

How stark?

It might depend on how seriously our society takes the threat.

"If this invasion persists, in 100 years' time, you're going to have a very different kind of forest," Görres said.

The zinger: In the long run, we might end up with fewer sugar maples (Amynthas proliferate in calcium-rich soils, where the trees also thrive) and more artificial pancake syrup.

"Think about the conversations you'll have with your grandkids," Görres said.

Banned in Wisconsin

Amynthas is known more commonly as the "crazy-snake worm" or "Georgia jumper."

It is larger than the red wrigglers that most commonly populate vermiculture boxes. The worm sports a distinctive, light-colored band.

The worm's behavior, though, is a real standout. It slithers in S-shaped lines, like a snake. It is feisty, capable of thrashing its way out of a bait can.

Seen over the course of a growing season, the worm is a standout, with a prodigious appetite and reproductive capacity.

Unchaperoned in the woods, the crazy-snake goes crazy, devouring and diminishing layers of moist leaf litter and mulch — "seed banks" that are critical to forest regeneration, Görres said.

The subsequent decline of the understory promotes erosion, deprives ground-nesting birds of cover and drives deer to browse more aggressively on mature saplings.

Görres' colleagues — academics, field scientists, students and master gardeners — have been documenting the worm in action on campus, in Jericho, Huntington, Shelburne and throughout Vermont, the exception being the Northeast Kingdom.

The worm detectives have tracked the spread of Amynthas through mulch-and-leaf piles, nursery plantings, greenhouses and backyard compost piles and gardens.

Scientists elsewhere in New England and the Midwest are in agreement: This is no garden-variety earthworm. Wisconsin six years ago banned possession of the worms.

Circle the wagons

Earthworm invasions are nothing new to these parts.

The last major glacial scouring (receding roughly 12,000 years ago) took care of any worms that had plumbed the continent's North Country soils, Görres noted. All 14 of Vermont's "native" species are imports, courtesy European settlers. Some of those worms, like the humans, have altered forest ecosystems.

Worms thriving in the relatively sunny South advanced as the ice retreated, but apparently at a slower-than-glacial pace.

How slowly?

"About 10 meters per day, maximum," Görres said. "But they don't have to move 10 meters per day. If the food resources are right there, why should they?"

Over the course of 1,000 years and under optimum conditions, he added, the fastest worms could rack up about 10 kilometers. And rivers and other barriers likely stopped stopped hordes of northbound worms in their tracks.

Amynthas' first presence in the U.S. was documented in 1937, in Arkansas — likely as a horticultural import from Korea or Japan, Görres said.

Joseph Schall, a professor emeritus at UVM's biology department, has worked closely with Görres in the quest to make better sense of local crazy-snake populations.

Genetic "fingerprinting" of the worm, overseen by Schall, revealed the presence of not just one species, but at least three — all of them alive and well in Japan, where they are likewise considered forest invasives.

The very term "invasive" is problematic, given the eons-long mobility of lifeforms, Görres noted: "Remember — not all invasions are successful."

Like rabbits

Is there something, in either hemisphere, that can slow down the crazy-snake worm?

Under Schall's guidance, Erin Keller, a UVM honors biology undergraduate, probed, literally, into the question.

She discovered that the parasite, Monocystis — a cousin of the organism responsible for malaria in humans — chows down on Amynthas sperm cells.

But, Schall noted in an email, even a "partial castration" of a worm by millions of tiny parasites appears to be no impediment to going forth and multiplying.

"The jumping worms are famous among biologists for switching to parthenogenetic reproduction, that is, no sex is needed," he wrote.

"One possible explanation for this odd behavior is that — if your sperm are being eaten, why not just give up on being a male at all? (The worms are hermaphroditic, having both male and female parts.)"

That reproductive talent, he added, is "bad news" because "just one worm may be able to establish an infestation at a local site."

A bit of good news: Cold weather doesn't agree with Amynthas, which apparently arose in the subtropics.

A couple of hard frosts and the vast majority of the little beasts are goners, explained Görres — although some adults seem to persist a little longer next to building foundations, above warm-fermenting septic systems and beneath clothes-dryer vents.

He followed up with some not-so-good-news: The crazy-snake worm's egg-like cocoon is winter-hardy when soil temperatures dip as low as minus 12 degrees.

Even worse news: Unlike many of its competitors, which go into a sleepy state during summer warm spells, Amynthas maintains its heavy-feeding habit, increasing its chances for local dominance.

The microorganisms inhabiting its gut seem to be uncannily effective at helping Amynthas digest woody debris, including mulch, Görres added. And the crazy-snake's fast, mid-season metabolism apparently allows the worm to outgrow the jaw size of its most promising predator, the red-backed salamander.

Micro-managed?

Other of Görres' collaborators have unearthed even wider, worrisome aspects of the crazy-snake's rise:

• Greenhouse gas: Meghan Knowles, a graduate student at UVM's Plant and Soils Science Department, is investigating how the worm's transformation of the forest floor affects the storage and release of atmospheric carbon.

Early results suggest a disruption to cycles, Knowles said.

• Mobility of heavy metals: Justin Richardson, a Ph.D. candidate at Dartmouth College, has found Amynthas absorbs a large portion of the lead and mercury that it wolfs down with soil.

There is a potential for the creature to play a part in future field-remediation projects, Richardson said. But those toxic metals more immediately pose risks to mammals and birds that feed on the worm, potentially "biomagnifying" the risk throughout the food chain.

To stay abreast of such risks, Görres said, we need to redouble research efforts — and before that can happen, we need to re-set a cultural bias that uniformly champions worms' work.

Examining a trio of euthanized and preserved Amynthas in his lab, Görres lamented our steep learning curve.

"Worms have 'street cred,' " he said. "In my work, I'm constantly challenged by people who say, 'What do you mean? Earthworms are the good guys!'

"We want to be careful with earthworms," Görres added. "I don't mean that we'll ever control them, but we need to manage them."

He eyes the approach of mandated composting in Vermont as the occasion for a statewide heads-up.

Act 148, passed in 2012, has a deadline of July, 2016, for composting of all residential lawn scraps. By mid 2020, all our household food scraps must be diverted from landfills.

Leftovers

Crazy-snake worms, prized for their digestive efficiency, already thrive in backyard and community-garden-sized compost piles.

In the absence of heightened vigilance, might more of them go free-range in the coming decade?

Almost certainly, said Tom Moreau, general manager at Williston-based Chittenden Solid Waste District — but probably not at industrial-scale compost outfits such as Green Mountain Compost, which the district operates.

"I've never seen a live worm in any of the compost we've sold," Moreau said recently, adding that uniform, intense heat also wipes out worm cocoons.

There is a consensus among other municipal composters that worms don't make it through their grinders, sieves and heating cycles, he added.

But Act 148 will further stimulate Vermonters' inclination to transform leftovers into rich fertilizer — with the help of worms, Moreau said.

"We've sold 4,000 to 5,000 home composters in the last five years," he said. "People know they can't afford to smelt and recycle aluminum cans in their back yards, but they sure as heck want to save money by composting."

The transfer of crazy-snake worms from compost to seedbed, from mulch to property margins, has become increasingly vivid to Moreau, who is an avid hiker and hunter.

"It's amazing. I've returned to places that in the space of three years have lost their understory," he said. "It's now a bare forest floor."

Contact Joel Banner Baird at 802-660-1843 or joelbaird@FreePressMedia.com. Follow him on Twitter at www.twitter.com/vtgoingup.