Nav: Home

Heat kills invasive jumping worm cocoons, could help limit spread

June 20, 2019

MADISON, Wis. -- New research out of the University of Wisconsin-Madison Arboretum shows that temperatures of about 100 degrees Fahrenheit kill the cocoons of invasive jumping worms.

That's good news for ecologists and horticulturalists who are working to slow or stop the spread of the worms, which can damage the soils they invade. Common practices that raise the temperature sufficiently could limit the ability of worms to spread through paths such as compost or potted plants.

But this study is just an early step -- little remains known about the life cycle of these invaders or how to stop them.

"We've been focused on the cocoon stage of the life cycle because we think that's one way they are being spread. They're small and hard to see so they're easy to spread on shoes, equipment or soil," says Brad Herrick, the Arboretum ecologist who co-led the recent study. "We wanted to try heat because in Wisconsin and many other states, commercially produced compost must be heated to 55 degrees Celsius, a treatment that we thought could kill the cocoons."

Herrick and Arboretum research specialist Marie Johnston published their findings in May in the American Midland Naturalist journal. Herrick has been studying the jumping worms, named for their characteristic thrashing when disturbed, since they were spotted in Wisconsin for the first time in Arboretum forests in 2013.

For the new study, Johnston and Herrick collected individuals from the two jumping worm species that have invaded the Arboretum grounds. The team housed groups of worms in colonies, fed them with leaf litter and collected all the cocoons each colony produced until the end of the reproductive season in late fall. Mating wasn't a concern -- the worms are parthenogenic, able to reproduce on their own.

In all, Herrick and Johnston collected hundreds of cocoons. Then they exposed the cocoons to temperatures ranging from 20 to 60 degrees Celsius for three or 15 days.

The cocoons were extremely sensitive to heat. Any treatment at or above 40 degrees Celsius (104 degrees Fahrenheit) killed all jumping worm cocoons in just three days. Because of variation in how hot their incubation ovens actually got, Herrick and Johnston pinpoint the lethal temperature to somewhere between 81 and 100 degrees Fahrenheit.

"What this tells us is there is a limit to what temperature cocoons can survive in," says Herrick. "If a pile of compost, which we know is a vector for earthworms, is treated right to temperatures at 40 degrees Celsius or above, then that pile should be jumping-worm free."

But, Herrick points out, that doesn't make heat a cure-all. Even if compost is sterilized properly, it could still get contaminated by cocoons after the heat treatment is done. Plus, ecologists believe worms spread through many other pathways that aren't exposed to high temps, such as dirty equipment or shared plants.

And while temperatures of 100 degrees Fahrenheit killed cocoons in the lab setting, cocoons could be much hardier if the temperature was raised more gradually or if they were in soil and leaf litter rather than glass vials. Herrick and Johnston are now testing cocoon viability under these more realistic conditions.

Nonetheless, the confirmation that sufficient heat can interrupt these invaders' life cycle is welcome news as Wisconsin and other states work to limit the northward spread of these damaging invaders.
-end-
Eric Hamilton, (608) 263-1986, eshamilton@wisc.edu

DOWNLOAD PHOTOS AND GIF: https://uwmadison.box.com/v/worm-cocoons

University of Wisconsin-Madison

Related Research Articles:

More Research News and Research Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.