Q&A: the DARK SIDE of wiggly worms

Living North: Why earthworms?

Hale: First of all, most people don’t know that there are no native earthworms in the Great Lakes region, none, zero, zip. So all earthworms they know and love came over with the Europeans. And while everything you’ve heard about earthworms being good in the garden — they aerate the soil, make organic material, increase nutrient turnover — that’s all true. But if you take that same earthworm and put it in a hardwood forest that has evolved for 10,000 years with no earthworms then it literally changes the ground rules (pun intended!) of that ecosystem which developed under earthworm-free conditions.

LN: How can they be bad for forests while good for gardens?

Hale: When earthworms invade these previously earthworm-free forests, they mix the thick layer of spongy, slowly decomposing matter we call duff, into the soil, which changes the structure, the chemistry, and the biology, the living organisms in the soil, literally eating the rooting zone out from under the forest understory plants.

LN: You were on the front page of the Wall Street Journal in 2003 and this story has been told many times since, most recently in the March Scientific American. What’s new in this research area?

Hale: There’s a suite of Asian earthworms in the genus Amynthas that are a new emerging threat to Minnesota. You’ll hear them called Jumping Worms, or Alabama Jumpers. They’re called that because they have very muscular and hyperactive behavior, very un-worm-like behavior. These guys flip and jump. They’ve been invading throughout the east coast and are slowly working their way west. In gardens they’ve invaded it’s been devastating, to the point of a “nothing grows here” syndrome.

LN: Have you seen these worm devastations? Are they in Minnesota?

Hale: There’s a guy in Pennsylvania who has 30,000 Hosta varieties and this Asian worm came in with mulch he imported and it destroyed half of his nursery. In Minnesota, we’ve seen them at a few places in the Twin Cities and a handful of places in Wisconsin. They’re not well-established in the western Great Lakes region yet but they’re poised to be coming. They have the potential for even more of a heavy impact on our native forests, but also having very negative consequences to ecosystems where you traditionally think of earthworms being good, like gardens and landscapes.

LN: Worms are legless. How do they get around and “invade” an area?

Hale: The European earthworms, nightcrawlers, and the like, are largely spread by people dumping unused fishing bait, gardening and earth-moving projects, like road construction. The Asian worms are spread much more by compost and leaf mulch, especially through larger community or commercial operations. So if you’re a landscaper and you’re ordering a truckload of compost or mulch from anywhere east of here, you may well be getting these Asian earthworms, unbeknownst to yourself. However, in bagged compost and mulch, the kind from Menards or wherever, there won’t be live earthworms or viable egg cocoons.

LN: I have a friend who composts and swears by the worms she puts in it. She says they’re needed to break down the waste to make it into compost.

Hale: There are two ways to compost: vermicomposting (with worms) and regular heat-generating composting. I’m an organic farmer so I compost in big black barrels in my back yard. But if you go out on the Internet and order what you think are Red Wigglers — which are also European but generally are fine here because they don’t survive Minnesota winters well — you may be getting these or any number of species. There are very few sources that we looked at that are pure Eisenia foetida (red wigglers or manure worms). Most people think they know what they have, but they don’t, or they have a mixture of different species. I met someone who had Asian worms in her compost, and I told her it’s not the worm she thinks. She said, “But they compost really well!” I said, “I bet they do.” One of the characteristics of Amynthas, the Asian worm, is they have an extraordinarily high metabolism and they can live in very high densities. So that makes it a really good compost worm and makes for big impacts in the ecosystem,if they get established.

LN: So what do you suggest for compost-minded gardeners?

Hale: Well, just remember, all earthworms are exotic, so it’s technically illegal to knowingly introduce them into the state if they’re not already established. We recommend that outdoor composters use a traditional backyard pile (or a compost barrel you can find online) that is turned and watered regularly. 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. Some people are just impatient. They want their compost in weeks instead of months and vermicomposting is a way to do that. But a standard “hot” compost pile is very effective and doesn’t have unintended consequences. If you compost outside in a backyard pile, rather than a container of some kind, and if earthworms are present in your yard, they will probably find their way there and live on the edges very happily. I worry less about this scenario because they won’t survive in a well-managed “hot” compost. However, you should never add any earthworms to your outside compost intentionally. Apartment dwellers and condo dwellers like vermicomposting because they don’t have the backyard space. We recommend that they freeze the vermicompost before they introduce it to an outdoor environment. That would kill the worms and their egg cocoons. If you have an unheated building, you can put your composting in a container in there and it will freeze solid over the winter and it will be fine. But if you put it outside and it gets covered with snow, it probably won’t freeze solid because of the snow insulation.

LN: Where are we most vulnerable when it comes to these worms establishing themselves locally?

Hale: We’d first see them around municipal gardens and compost sites because mulch is being brought from far away and they are fairly uncontrolled. On one level, the community garden and compost sites make a lot of sense. On another level they’re dangerous, because they bring not just worms but Creeping Charlie, weed seeds, buckthorn and garlic mustard. We’re bringing all that to one site, mixing them up and sending them back out. It’s a recipe for disaster; a perfect mechanism for distributing invasive species unintentionally.

LN: There’s probably a lot more information you could share with us. How can we help keep these worms out and where can we learn more?

Hale: We’re always looking for citizen scientist volunteers to help add to our database of earthworms. It’s the largest, to my knowledge, in the world! Just go on the Web to greatlakeswormwatch.org for more information, how to get involved and to order my book. Educators get a discount for 10 or more copies. We are happy to send people vials so they can send us earthworm samples to identify. All the information is there for how to collect and submit samples to our database!

Tags: ln newsmaker, livingnorth