Asian Jumping Worm, Amynthas agrestis

Are Those Worms Really Good for Your Garden?

by Donna Calcavecchio

So you thought worms were your friend? Think again!

The worms we think of as our “native” garden friendly earthworms are actually not native to the northeast. When the last glaciers receded they scraped the soil and took the native earthworms with them. So where did our worms come from? Most came from Europe possibly hitchhiking in the soil of imported plants. Many of these worms are beneficial, but the Asian variety which have become ubiquitous in my garden are not.

The Amynthas agrestis worm is often referred to as the “crazy,” “jumping,” or “snake” worm. They are big and very active and can move like snakes. They stay very close to the soil surface and feed on organic matter. That’s your mulch, compost and leaf litter, all of the things you add to your garden beds to help promote healthy plants and to eliminate weeds.

…They love mulch and go through it as though there was no tomorrow. Eventually you get wise and stop feeding them that mulch. Yes, they can decompose woody mulch. They stimulate the production of lignin decomposing enzymes.… You even see them in decomposing logs.” Josef Görres, Plant and Soil Science, University of Vermont

I first noticed these worms in my garden a few years ago. They were in the most shaded areas and didn’t seem to be a problem — other than totally creeping me out.

The cool, damp weather we’ve experienced this summer has changed that dynamic drastically. The invasive worms are now in every corner of the garden, lawn and even in the gravel driveway. My beautiful, statuesque hostas (usually 2-​​3ft high), didn’t get any larger than 3 inches and look malnourished. The well established astilbes (false goatsbeard), came up briefly, (maybe an inch high) before disappearing completely and I fear for the spring ephemerals.

Huge piles of worm castings are everywhere.

Amynthas worm castings

Amynthas worm castings encircling a large maple tree.

Is the Asian jumping worm really that bad? The answer is yes.

Not only are they posing a threat to our gardens, but they have the potential to create a severe change in the make-​​up of the forest under-​​story and in doing so change the landscape significantly.

Forest Understory

the worms create a soil made predominately of minerals rather than the organic matter that forests need to flourish.

As they speedily devour the natural accumulation of organic matter on the forest floor —necessary for seedlings to flourish — they create a soil made predominately of minerals rather than the organic matter our forests need to flourish. Not only are the forest trees threatened, so too is the wildlife who depend on the forest for sustenance and shelter.

The Amynthas worm reaches maturity in 60 days, much faster than the European Lumbricidae species at 120, thus allowing for two hatches a season. They have voracious appetites, are highly adaptive to temperature changes and the cocoons overwinter. They out compete non-​​native European species and produce a unique soil signature that has the potential to change our landscape.

What can you do to keep the Asian Amynthas worm out of your garden?

Keep the garden clean, pick up piles of debris as soon as you prune— they love the dark, damp environment these piles can create.

If you don’t already have the worms, use onsite mulch.

Mow leaves into lawn rather than raking into piles.

Do not share or move plants if you suspect Jumping worms.

Check plants before you purchase.

Buy certified soil, mulch and compost. Be sure to ask where it comes from.

Speak to your local nurseries and if applicable, your landscaper and find out if they have encountered the Amynthas worms and how they are dealing with them.

Call your local Cornell Cooperative for information on local infestations.

What can you do if you find them in your garden?

So far there is no recognized way to kill these worms. I recommend that you refrain from using pesticides as they can harm populations of beneficial insects.

You can catch them, —be forewarned, they are very fast and squirmy — put them in a black plastic bag and place the bag in the sun.

Some golf courses have reported success with an organic fertilizer made by Ocean Organics that seems to help keep the populations under control. The active ingredient is tea seed meal, a highly effective organic fertilizer with a high content of protein and saponins. The application of this fertilizer drives the worms to the surface where they die from being exposed to the sunlight. It’s the same premise as the black plastic bag, but sounds much easier than trying to catch hundreds of squiggly worms.

What will I do now that I’ve discovered the worms in my garden?

My plan is to scrape up all of the piles of worm castings that I see in the garden, lawn and driveway, put them in black plastic bags and let them bake in the sun. Then I’m going to rake up all of the garden debris as my plants go into dormancy — I will leave seed heads for the birds, but nothing else— and I will scrupulously rake ALL of the leaves as they fall and put all the leaf and plant debris in black plastic bags and leave those bags in the sun. If I can find a source for the aforementioned fertilizer, I will spread it on the lawn and garden before the first frost to force as many worms to the surface as possible. I may not put any mulch on the garden —I don’t want to make it any more hospitable than it already is.

Hopefully we’ll know we’ve been successful in the Spring as temperatures warm the soil. Stay tuned!

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