Jumping Worms Are Invading the US. Here’s How to Fight Them Off.
They may be dangerous, but they’re not infallible. With just a few simple tricks, you can help root them out and keep them from spreading.
Asian jumping worms are a recent arrival to North America — and they’re a dangerous one. Technically, most of the worms that Americans and Canadians are used to seeing aren’t truly native; the continent’s own worms are thought to have died out during Earth’s most recent ice age. But jumping worms in particular are considered especially dangerous; they can ward off predators more effectively, present an active danger to the soil they reside in, and devour organic matter at an alarming rate. I’ve written in greater detail about exactly why they’re so threatening in a separate article.
There’s also a small catch to all this. What’s known collectively as the “Asian jumping worm” is actually a grouping of three similar, yet separate worm species all hailing from Japan: Amynthas agrestis, Amynthas tokioensis, and Metaphire hilgendorfi. Interestingly, we can learn a lot by investigating Japanese resources on each of these species, even if there exists a language barrier. This, too, is something I’ve written about elsewhere, and this strategy is particularly helpful for identifying the different types of jumping worm which normally get lumped together — perhaps unfairly so — into one category by English resources.
But if you’re simply looking to do your part in curtailing these worms’ impact on North American ecology, what should you do? To start, here are a few suggestions from two East Coast resources, one published by the University of Connecticut, and another by the University of Maryland:
Cook your soil!
- They may be more active in the heat, but jumping worms can be killed outright if they’re exposed to temperatures above 105°F (40.5°C). A longer “cook” time makes it even more likely that they won’t survive — you may wish to use three consecutive days as a minimum.
- Before you add soil, mulch, or compost to a garden bed or agricultural plot, make sure it’s been heat-treated, either by yourself or by whoever is providing it to you.
- If you want to perform your own heat treatment, the best time to do it is in the summer. Sandwiching soil, mulch, or compost in between two large sheets of clear plastic can trap enough heat to kill any worms. Placing rocks or other weights around the perimeter can also help keep both heat and worms trapped so they can’t escape.
Scout your roots!
- Whenever you transfer a tree or other plant from a pot into the ground, you’re also moving the soil it’s been growing in — and there’s a chance that the soil in question could be housing jumping worms.
- To prevent their spread, try to dislodge the soil from the roots before planting. This also gives you a chance to spread out and loosen those roots, which can be especially helpful for the plant’s growth if it’s been cramped up inside a small pot—just be careful to not damage the root system while doing so.
Clean your boots!
- This is especially important in spring, when jumping worm eggs are most likely to be mixed in with the soil.
- If you happen to walk over an area with these eggs, you’ll want to ensure you don’t track them into a new area where they previously didn’t live.
- This also applies to tools if you use them in multiple places; wash all the dirt off of them before you bring them somewhere new. It may seem redundant, but it’s an incredibly effective (and simple!) way to minimize risk.
Plant with care!
- Jumping worms tend to only inhabit the top layers of soil, mostly staying within 2 inches of the surface. If you’re worried about a jumping worm infestation where you’re planting, you can take advantage of this fact by focusing on plants with deep roots.
- This also opens the gates for setups like companion planting and pollinator gardens, which can provide ways to introduce more deep-rooted plants to a garden which might not have many otherwise.
Fishers beware!
- It’s theorized that Amynthas agrestis was first brought to North America as fishing bait, and spread when fishers who used them discarded their unused worms — likely under the false impression that, being worms, the local environment could only stand to gain from their presence.
- It’s not unlikely that the Fukisoku and Hitotsumon worms were introduced in similar ways; the CAES report in particular notes that jumping worms were used to feed zoo platypuses in the late 1940s.
- The most important thing fishers can do to keep jumping worms from spreading is to verify what species of worm they’re buying as bait — or simply use other bait besides worms.
- Even if they’re labeled, though, different worm species can often look similar enough to cause some confusion. With that in mind, resist the urge to throw them out into the wilderness, and find alternate ways to kill or dispose of them, such as freezing them or drowning them in soapy water.
All of these are considered good practices when it comes to preventing jumping worms from reaching new areas. But what about removing them from places they’ve already established themselves in?
Sadly, there aren’t many good solutions at the moment. The Connecticut Agricultural Experiment Station has compiled a laundry list of potential threats to jumping worms, but not all of them have proven viable, and they even advise against several of them entirely. Notably, the list includes things like introduced predators (such as the hammerhead worm) and chemicals which may do just as much harm to plants as they do worms (such as vinegar).
But even if their effectiveness varies wildly, there’s one solution which stands out in its stability: hand-picking. It may not be quick or flashy, but it’s about as good as we can get. If you’re doing gardening, yard work, etc., then this can be as simple as bringing a sealable bag or a bucket of soapy water along, so that you can remove and kill them when you see them. Of course, being able to identify jumping worms is a must for this method — more on that here.
Additionally, there’s one other strategy that works well alongside hand-picking. Mustard solutions can be used to agitate worms, goading them into crawling up into the surface. This isn’t a fix by itself (the worms will eventually re-enter the soil if left on their own), but it does make hand-picking a great deal easier. As an added bonus, it’s safe for plants. CAES recommends mixing 1/3 cup of ground mustard seeds with 1 gallon of water for each square foot of land.
The fight against these jumping worms is still just starting in North America, and it has yet to be seen how they’ll shape the continent’s ecosystems — or whether we’ll be able to prevent their most deleterious effects. But by keeping a lookout for them, and by learning from their home regions how to identify and control them, we can make great strides in stopping them before they spread any further.
