Worms: friend or foe?

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Worms: friend or foe?

Postby Tigger » Mar 15, 2007 7:47 am

A must-read article published today in the New York Times.

I had heard about this a few years ago, with the disappearance of native trilliums from (in particular) the eastern forests. Evil European night-crawlers!
The Dark Side of a Good Friend to the Soil

By ANNE RAVER
I’VE always thought of worms as my friends, until I started talking to ecologists who have been studying their voracious appetite for leaves.

“Your grandmother was wrong all these years,” said Dennis Burton, an ecologist at the Schuylkill Center for Environmental Education in Philadelphia.

Worms may be good for vegetables and flowers, but for trees and shade plants they are a large and growing menace. In an agricultural field or a vegetable garden, worms help decompose organic matter, churning nutrients back into the soil. Their constant tunneling aerates the soil, creating pathways for air, water and plant roots.

But in forests in the Northeast and parts of the Midwest, worms are proliferating and consuming leaves at such a pace that they are actually destroying the duff, the thick leaf litter that nourishes tree seedlings, prevents erosion and protects woodland plants from disease and insects.

They are wreaking havoc in woodland gardens, too. Barbara and Robert Tiffany, who tend four acres of shade-loving plants at their home, MillFleurs, in Point Pleasant, Pa., have watched their prize-winning, four-foot-wide hostas shrink to half their size.

The Tiffanys first noticed that their hostas were shrinking two years ago. This was a crisis: they had promised to show off their 1,100 hosta cultivars to the American Hosta Society at its national convention last June in Philadelphia.

“I had no idea what was happening,” Ms. Tiffany said.

They thought their water might be the problem, so they had it tested. But the water was fine. Then they noticed “gazillions of worms,” Ms. Tiffany said. “Every time I would stick a trowel into the soil, worms would pop up or skitter away. They were so energized, not like the worms of my childhood.”

Mr. Tiffany did a little research and learned that the Northeast and the Great Lakes region were plagued by worms. They sent a few of their worms to Cindy Hale, a scientist at the University of Minnesota, who identified them as Amynthas hawayanus and Lumbricus terrestris, two species that are invading the Northeast.

The Tiffanys realized, in retrospect, that they had been helping the worms proliferate by carting in mulch for paths and top-dressing plants with compost.

They recalled digging up one prized hosta, a four-footer that had been reduced to two feet, and counting 19 worms as they fell from its roots.

The roots, normally so fleshy and vigorous, were stunted and sort of shredded, “as if something had eaten them,” Ms. Tiffany said.

“Earthworms were not meant to be in a forest,” said Anne Bower, a conservation biologist at Philadelphia University who explained that northern forests evolved without worms. “Their decomposers are fungi, microflora and fauna, which release nutrients very slowly,” she said.

Worms arrived with the Colonists, who came in ships often weighted with rocks and soil, for ballast. The settlers brought plants, too, which carried worms and their eggs in plant roots. Over the centuries, of course, imported plants added to the exotic worm population; so did the fishermen who tossed their bait worms along the banks of streams and lakes.

In fact, the night crawler, Lumbricus terrestris, native to Europe and a favorite for baiting fish, is a big eater in the forest.

“It’s an anecic species, a deep diver,” Mr. Burton said. “It burrows deep into the soil, pulling leaf litter with it.”

Another invasive worm, an Asian species, Amynthas hawayanus, is epigeic, meaning it stays close to the earth’s surface, living in the topsoil and the duff layer.

“It’s like a rototiller running around the surface of the forest,” Mr. Burton said.

Both these worms, among others, have higher populations in urban and suburban areas than in rural areas. This makes sense, because they first came in through seaports and are often spread by gardeners who not only purchase their plants but also trundle mulch and compost into their woodland gardens.

The Asian genus, Amynthas, was first noted in New York and Connecticut in the late 1980s by ecologists working for the Institute of Ecosystem Studies in Millbrook, N.Y. They were trying to analyze the health of forests in a 100-mile radius of New York City.

These worms change the very chemistry of the soil, because their gizzards emit calcium carbonate, which acts like lime on acid soil, making it more alkaline. That may be nice for corn and sunflowers, but it is not good for azaleas and oaks, which thrive in acid soil.

The worms are also breaking down organic matter so quickly that the nutrient overload is injuring plants and running off into streams and lakes. Invasive plant species, like stiltgrass and garlic mustard, which thrive on heavy nitrogen, then move in.

How do you find out if you have too many worms?

Look for signs of invasive worms, such as a thinning forest floor or even eroded open spaces. Another sign is a noticeable lack of spring ephemerals like trillium, mayflowers and trout lilies, which are disturbed by all these tiny plows shifting the microbial community from fungal to bacterial.

To test for worms, mark off a section of your woodland garden or forest about three feet square. Then wait for a heavy rain (this test will not work in dry soil).

If the soil is moist, apply a hot Chinese mustard solution, made by mixing two cups Chinese mustard with 10 ½ quarts of water. Sink five coffee cans, tops and bottoms removed, about an inch into the ground of the marked area, then pour the mustard solution into the cans.

“The mustard solution will go straight down and the worms will come up,” Ms. Bower said.

If more than five worms pop out, you have a problem. In rural areas Ms. Bower’s researchers have found only about two worms per three square feet; “in the city we’re getting 89,” she said.

Ms. Bower and Mr. Burton have been testing various organic controls, like tobacco, walnut shells and pine needles. They were not effective. Sulfur pellets, however, mixed with oak leaf mulch, which is acidic, showed promise. Simply follow the directions on the back of the sulfur bag, and do not apply more than is recommended. (Soil that is too acidic will have its own problems.) Then spread out a couple of inches of the oak leaf mulch. The Department of Agriculture lists earthworms as beneficial organisms, so using a pesticide to kill them is technically illegal.

To avoid having so many worms in the first place, be sure not to feed them by spreading wood chips or compost in paths in the forest. Do not toss grass clippings, another favorite worm food, next to the woods, either. And do not toss out fishing worms or red wrigglers by throwing them on the ground or in a pond (they do not drown).

If worms are destroying your woodland plants and you have no choice but to kill them, they can be put in alcohol, frozen or collected in a bag and sent to the landfill.
Not sure I'll go so far as this mustard test, but it's a thought. (we still have plenty of mayapples, so things must not be too bad)

I'm tempted to cross-post this to the Garden Bench and the Shade Garden forums. You think, Chris?
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Worms: friend or foe?

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Postby thy » Mar 15, 2007 9:02 am

Interesting- scarry- do not know what to say !!!

But not convinced, City areas are more poluted from cars and factories and from my old ecologian book- they are to blame for planth death.
The lack of worms in the country areas are told to be from non organic fertilizer and pesticides ..

15 years or so ago a huge area in mid Germany had a forest death- millions of pine trees died- could be interesting if the looked for worms in the area, but have no idea how to find out

Waiting for Hank to post. Remember his postings a few years ago about schrinking hostas ?
So Hank, did you look for worms ?

If this is correct- it is turning everything upside down

Thanks for posting

Pia
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Postby renaldo75 » Mar 15, 2007 11:24 am

Very interesting read, Tigger. I have worms here, but not excessive #s of them. I'm in a town - definitely no forest canopy here. But several years ago after I had created the bed I call W2, there was a fairly heavy spring rain. I was out walking one morning & there were tons of worms/nightcrawlers out in the streets. I went back home & got a 5 gallon bucket & filled it up. :o Pretty easily. Then took them home & scattered them on W2. That would have been in 1999 if I remember correctly. I've dug in there since then [planted hostas there in 2003 & 2004] & have found relatively few worms in the top foot or so. I've always thought that was odd, but they may just be deeper in the soil than I was digging.
GO HAWKEYES!!!

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Postby Tigger » Mar 15, 2007 2:02 pm

I think a take-home message from this is: if you have a smaller shade garden and do your own leaf clean-up in the fall and (probably) apply some hardwood mulch, you shouldn't be too concerned. But if you have a woodland garden where you would want the natural leaf fall to serve as a major mulch source, then the (exotic) worms will turn everything into fluff too quickly. This tends to bury your hostas faster than they can push themselves up to their desired surface level.

Pia, remember that the North American forest flora have adapted to quite different conditions than that of northern Europe. Your forests are accustomed to this worm activity; ours are not! I wonder if the same thing is happening in Japan and eastern Asia (which is more like North America)?

Renaldo, worms (like slugs) will go where they want to. Maybe they didn't like W2?
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Postby caliloo » Mar 15, 2007 3:34 pm

I ahve TONS of worms im my planting beds, both sun and shade and I always thought this was a GOOD thing. I have been adding coffee grounds to all the beds for several years and it has paid off with a huge worm population. Now I find out it is a bad thing? SHEESH!

I remember many discussions about the Tiffanys problems with their beds - I had no idea the end result was attributed to worms. THis is especially disturbing to me since i live about 20 minutes from them and know I have a ton of worms.

I do know of a quick and easy method of killing them - I discovered quite by accident that Bayer Superior Rose Care (aka Bayer 3-in-one) will kill ALL the worm population within a minute or so.

I had been given a sample and decided to use it on one of my blackspot magnet roses. I mixed it up according to the directions and poured it on. Within 10 - 20 seconds there were several worms writhing on the surface of the soil. Within a minute, those worms were dead and there were 12 or so that had surfaced and were also writhing madly in obvious distress. They were all dead within just a couple of minutes. I inquired about it on another rose forum and one of the soil gurus over there reviewed the ingredients and said that one of the active ingredients is definitely lethal to worms.

I had decided not to ever use the product again since I was so happy I had so many worms, now I am rethinking this.

I will cetainly be watching this post with interest to see what every one else thinks about this......

Thanks Dave for posting the article. Very interesting!

Alexa
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Postby thy » Mar 15, 2007 5:14 pm

Never seen anything looking like a worm biten root, but we do have a lot of small digging critters, who probably made it to the US too- think you have to have much more evidence before you think as worms- even European or Asian worms - to be a pest

Gallio- hope you told the compagny :evil:

Pia
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Postby thy » Mar 15, 2007 5:18 pm

By the way Lumbricus terrestris sure look like my sort of worm ( pics from Google)- how do your worm look like ? :lol:
:D Pia
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Postby Hank Zumach » Mar 15, 2007 7:48 pm

Pia--Wow!! Do you have a good memory. :o I have never found a reason why some of our hostas have gotten smaller. We do hve worms here in our woodland garden but I have never noticed an unusual number of them when digging in the garden so I don't think worms are a problem here.
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