In the recent blog article Earthworms are Bad News for North American Forests, I wrote about the problem of invasive European earthworms in North America and the damage they are doing to forests, but that may be only be the start. Ecologists are even more concerned about a co-invasion from three newer introductions: Asiatic jumping worms (Amynthas agrestis, A. tokioensis and Metaphire hilgendorfi), also called snake worms or crazy worms.
They seem to have been introduced accidentally into the southeast United States in the 19th century, probably through contaminated nursery stock imported from Japan or Korea. But they’re spread into the North seems recent, within the last 15 years. They’re already present in all Northeastern US states and lately seemed to have pushed across the Midwest showing up here and there and now across the Rockies into Oregon and to have jumped the border into Ontario, Canada, although their presence is still very sporadic throughout this vast territory.
What Are They?
Jumping worms are large, plump earthworms, up to 8 inches (20 cm) in length, looking much like the common earthworm (Lombricus terrestris), also called nightcrawler or dew worm, but with a startling habit: they jump and thrash when disturbed! They’re very animated and tend to remain on the soil surface. Their subsequent movements are snakelike rather than wormlike, as they slither from side to side. As for why they’re called crazy worms, well, I think any earthworm that jumps when you bother it is likely just a bit crazy, don’t you?
They’re not just present in northeastern North America. They’ve become established many other parts of the world. In the southeastern US, where they’ve been around for more than a century, they may be called Alabama jumpers or Georgia jumpers. In Europe, when they are also now present and spreading rapidly, a different series of Amynthas species seems involved.
How to Recognize Them
If jumping and thrashing isn’t enough warming that these are not your average earthworms, look at the clitellum, the “ring” earthworms have around their body. That of the jumping worm will be smooth and light-colored, sometimes almost white, not almost the same color as the rest of its skin as that of the nightcrawler, and almost flush with the skin rather than bulging and ridged. They’re dark worms, almost gray in color, with a glossy smooth skin. They will occasionally lose their tails as a defense mechanism to escape predators.
Jumping worms don’t dig tunnels, nor do they feed underground, but remain near the top of the soil, in the top few centimeters, feeding on leaf litter. Instead of leaving their excrements in little piles of castings as is typical of nightcrawlers, they cover the soil surface with dry, grainy, pellet like castings that look somewhat like dry coffee grounds, keeping seeds from sprouting and destabilizing soils.
They are best recognized in late August and September, when they have reached their full size.
Unlike nightcrawlers, which can live 6 years or longer, jumping worms have an annual life cycle. The adults die in late fall, but leave tiny cocoons, difficult to spot, that overwinter. They have been known to survive temperatures as cold as -40˚F/C. They grow quickly in the spring, outcompeting and often eliminating other earthworms. Hermaphroditic, they can reproduce sexually, but also parthenogenetically, producing cocoons without fecundation, so it takes only one to start a new colony. There are two generations per year (three in mild climates).
One beacon of hope is that they seem to prefer neutral and alkaline soils to acidic ones, which could help slow their invasion some areas.
⚠️ Warning: Jumping worms are considered a prohibited invasive species in several US states and it is illegal to possess them with the intent to sell, import, purchase, transport or introduce them.
Jumping worms live in denser numbers than regular earthworms and thin the layer of forest litter (duff) at a speed unknown in other earthworm species, reducing it by 95% and leaving the soil essentially bare. The degradation of the litter is so rapid that the nutrients released cannot all be absorbed by the soil and plant roots. It’s like a fast-release fertilizer instead of a slow-release one and results in the impoverishment of the upper layers of soil, the compaction of lower layers and the pollution by nitrogen and phosphorous of nearby bodies of water.
Jumping worms also consume plant seeds and rob the soil seed bank of its reserves. As a result of that and of the environmental degradation they cause, the forest floor becomes depauperate in plant species. Native species, dependent on thick leaf litter are eliminated, mostly replaced by invasive exotic weeds. They are equally damaging in forest and prairie environments.
Animals are likewise affected. Salamanders and many bird species will not eat jumping worms, spitting them out or avoiding them after an initial tasting. Ground-nesting birds disappear. However, moles will eat them, so can be helpful in controlling them.
How to Avoid Jumping Worms
It is believed the current sporadic diffusion of jumping worms into northeastern North America has been largely caused by the transport of contaminated nursery stock and by their use in as fishing bait. For that reason, the following control methods can be helpful:
- Pay careful attention when sharing and moving plants. Always check for worms. Buy bare root stock when possible.
- Clean compost, soil and debris from vehicles, personal gear (including boots and shoes), equipment and gardening tools before moving to new sites.
- Do not buy or use jumping worms for bait, vermicomposting or gardening.
- Only purchase compost that has been heated to appropriate temperatures for a sufficient duration.
- Dispose of any live worms in the trash or place them in a bag and leave them out in the sun for at least 10 minutes. Then throw the bag away. Likewise, dispose of any fishing bait responsibly.
- Check your property for earthworms using a mustard solution. (Don’t worry, it’s harmless to plants!) Mix a gallon (4 liters) of water with 1/3 cup (80 ml) of ground yellow mustard seed and pour slowly into the soil. This will drive any worms to the surface. If you discover jumping worms, avoid moving plants or soil from your yard.
How to Control Jumping Worms
There is presently no viable control method for jumping worms, although studies are being carried out on possible repellents and pesticides, notably dousing the soil with products containing saponins, such are tea seed meal, and prescribed burning. Presently, the only effective control is preventing their spread.
You may not have jumping worms in your garden yet and, if so, that is a state you’ll want to maintain. Keep an eye out for this new invader!