Invasive Snake Worms
By Kerry Lake, Master Gardener
At our WMMGA community service project at the Hospice of the Fisher Home on a recent Friday morning, Master Gardener S.R. said to me that she thought we might have the Invasive Snake Worm in our garden beds. NOOOOOOOOOOOOOOOO my brain screamed, but in my heart I knew she was right. We walked to the garden bed where she had seen them and we noticed that the borage was not doing very well. A gentle pull of the plant and it came right out of the ground. A scrape of the soil, just a few centimeters down, and wait for it, there is one, and another, and a few moments later a third of these dastardly invaders.
What is this Worm? Crazy worm, Jumping worm, Snake worm are all names for Amynthas agrestis, Amynthas tokioensis, and Metaphire hilgendorfi.. These are an aggressive eater that devour the organic matter on the top of the soil in forests and gardens, even the ‘death strip’ at the side of roadways, leaving the soil granular looking, and dry.
Let’s first describe the earthworms that we are familiar with here in New England. Our usual earthworms are not native; the Glacials that scraped away our topsoil also took away the native earthworms. What we have today have come from Europe, in the pots of plants brought to our shores by our first settlers, and in the soil ballasts of the ships that brought the settlers to our shores. Our earthworms (Night crawlers are Lumbricus terrestris and Red Wigglers are Eisenia fetida) dig into the soil creating boroughs. They pull pieces of organic material (leaves, etc.) into their borough and slowly eat this dead organic material leaving behind their nutrient rich castings in the soil. These burrows provide space for water drainage and aeration of the soil, important factors for plants. These earthworms hibernate in the cold seasons digging their way deeper into the ground.
The Snake Worms look like our usual earthworm but with a few differences. First, they are an annual species that grow quickly in the summer months, sometimes reaching 12 inches long. They have a milky colored egg sack around their top half, but this band goes totally around their body, not partially like our familiar earthworms. Most importantly for the gardeners is the fact that they stay in the top few inches of the soil, quickly eating ALL the organic material, including the shallow roots of some of our plants, hence the failing borage that was easily pulled from the ground. Their behavior is different also. The Snake Worm will jump and thrash around when touched, even to the point of breaking off its lower portion if picked up.
What is the harm they do? As voracious eaters they are quickly consuming everything that they can in the upper few inches of the soil, including the top roots of some plants. Their rapid digestion means that they are leaving behind a large portion of casting, the nutrient rich ‘poop’ from worms. But this is not being produced at the right time of the season. It is mostly being produced in the late summer and fall, when a plant does not need fertilizing, instead, a plant needs to slow down any growth in preparation for the cold season. A second issue is that because these worms are eating the organic matter so quickly and leaving it on the top of the soil, a heavy rain can wash this composted material away. Now there isn’t much left for next year, or for the regular earthworms to process in their slower digestive manner. In fact, without the duff layer, there is nothing left for seedlings in our forests to sprout and grow. This change severely alters the soil ecosystem. In some cases on the forest floor invasives such as Garlic Mustard (Aliaria petiolate) have moved in.
Master Gardener K.C. adds “As gardeners, we dutifully add compost, shredded leaves, mulch, etc. And this is the very material that attracts the worms. More than losing plants to some secondary root damage, our very soil is degraded. Without healthy soil, all that we’ve learned as Master Gardeners goes out the window.”
The Snake Worm dies in the cold months. But they leave behind their cocoons, little 2mm brown sacks which are probably too small for any of us to see. These cocoons start to grow in early May, reproduce in midsummer for another crop, so by end of summer, you can easily have a bucket or two of them when digging around in of your garden.
How do I ID them? Because they are eating so rapidly, they are leaving behind a large portion of worm castings. Look for this in your garden. The castings are loose, very dry, granular coffee ground-like over a larger area than a small pile from our usual earthworms. Scrape or dig a little in this area, and they will soon appear. Touch one and watch its’ movement; flopping around, writhing like a snake, and I’m sorry to say that you have them too. (Note that they can move forward in the same manner as other earthworms, but it is when they are disturbed, i.e. touched, that their snake-like movement distinguishes them.)
What can I do? Well, as gardeners, we share our plants with one another and have probably passed these nasty worms on to each other’s gardens. We need to stop sharing our plants with one another. If purchasing any plants, not only take a look at the health of the plant in the pot, look closely at the soil. Is there a lot of worm casting? Lift the pot from the table or ground to determine if there are lots of castings under the pot. In either case, take a pass on this plant. Instead, start your plants from seed, or purchase bare rooted plants.
In August 12, 2019 Margret Roach shared her podcast with Brad Herrick, who is an Arboretum Ecologist and Research Program Manager at the University of Wisconsin – Madison Arboretum. His staff first noticed the destructive effects of this worm in 2013, in an urban setting, and he has been studying them since then. He suggests, yes, digging them out of your garden as much as possible. Put them in a can or container that they can’t wiggle out of. Then put them in a plastic zip-lock type bag, and solarize them (bake them in the sun for a minimum of 3 days). Then throw them out, NOT in the compost or back into your garden, but in your garbage to be taken away.
I want to add that this is the time (late summer) to take this action. In the spring, the new worms will be hatching from their cocoons which will be difficult to see. By mid-summer, our gardens should be lush, and again, difficult for us to see the excessive worm castings. (If a plant is not thriving, look closer at the soil. And take decisive action removing as many of these worms as you can.) Now in late summer the extra castings are easy to identify as we clean up our gardens at the end of the season. And the worms will come to the top of the soil with a little scraping of the soil. According to Brad Herrick, another way to bring them to the surface is to mix 1/3 cup mustard seed powder with a gallon of water. Spray or pour a little onto the surface of the soil. The mustard irritates the worm’s skin and they will come to the surface. Grab them (yes, you can wear gloves) and quickly put them into your container. Later, place them in the zip-lock plastic bag for the final step – solarization.
There is some research into a fertilizer called Early Bird that is being used on golf courses, but we don’t have any definitive information at this time. We certainly do not want to be using any type of pesticides (herbicides, insecticides, or fungicide) as we would be damaging far more than just a few earthworms.
Be sure that any compost you use has been thoroughly ‘baked’ to a minimum of 131F for 3 to 10 days. In that time, it should have been turned so that the entire material has been thoroughly ‘cooked’ to kill off any cocoons, along with bacterial matter, fungi, and other diseases.
Clean your tools and your shoes after each session in the garden. We don’t want to be bringing the cocoons back into our garden after we have eliminated the adults.
Please, do not gather them from your garden and to use for fishing bait. Let me repeat: DO NOT USE AS FISHING BAIT. Actually, with the way these worms jump around, it would be very difficult to get them onto the hook. If you are sold some of these worms as fish bait, do not release them into your landscape, but place them in the zip-lock type plastic bag and solarize them.
We have them at least in one of our WMMGA community service sites, so we know that each of us must have them at our Master Gardener gardens. (We donated plants to this site from our home gardens). We know that we have them in some of our local Community Gardens (we have seen the castings), and these worms have been identified at a local Historic Garden site. This is not a one-time problem. We all need to be vigilant in the next few years to keep our gardens healthy and growing and not to spread these invasive worms.
Many thanks to Master Gardeners Sharon Rogalski, Kendall Clark, and Bea Botch for their encouragement, knowledge, and sharing their favorite websites on this topic.
Learn more from these websites:
https://www.arboretum.harvard.edu/native-plants-crazy-snake-worm/ for the best photos of the worms and their castings
To learn more about the benefits of earthworms (not snake worms), read The Earth Moved by Amy Stewart. This is a fascinating book.