The State We're In

Sep 1, 2022

by Alison Mitchell, Co-Executive Director

Imagine digging in your garden and seeing an unusual-looking worm near the surface. You reach out to move it … and suddenly it thrashes violently and flies through the air!

It sounds crazy, but that’s the behavior of an invasive earthworm that’s causing concern among ecologists in the northeast.

These recently-introduced earthworms go by many nicknames: Asian jumping worms, crazy worms, wood eels, Alabama jumpers or snake worms. Native to eastern Asia and first found in Wisconsin in 2013, jumping worms may wriggle like snakes and writhe violently when touched, launching themselves into the air. Like some lizards, they can shed their tails to escape predators.

Jumping worms (Amynthas agrestis) will certainly startle any unaware gardener or angler that tries to pick one up! But the fright factor isn’t the reason why they’re considered a threat.

Jumping worms are listed as an invasive animal species in New Jersey and many other states because of their potential to dramatically harm forest ecology and reduce biodiversity.

According to researchers, jumping worms alter soil structure more than any other worm. Unlike most earthworms found in the Garden State (none of which are native), jumping worms live and feed close to the soil surface. Finding a new patch of ground, they quickly devour the organic components of the soil and leave behind castings resembling coffee grounds.

This change to the soil structure can be devastating to forests and the many native plants and animals that call them home.

The soils of healthy northeastern forests include a thick top layer of leaf litter and organic matter. Many native plants – which evolved without the presence of earthworms – need this organic layer in order for their seeds to germinate. When jumping worms consume the organic layer, native plants slowly die off and invasive species move in. This harms wildlife that depend on native plants, including ground-nesting birds, amphibians and invertebrates.

Jumping worms grow more rapidly, reproduce more quickly and consume more nutrients than other earthworms.

How do you recognize a jumping worm? They’re dark brown to grayish in color with a smooth, whitish band that completely encircles the body near the head. If you spot them in the top few inches of your garden or compost pile, or the leaf litter in adjacent woods, it’s probably a jumping worm. In contrast, the more common earthworms that have been around for centuries burrow much deeper in the soil.

But the real giveaway is their distinctive behavior when touched. If they wriggle like a snake and powerfully launch themselves, they’re jumping worms.

Currently, jumping worms are considered an “emerging” threat by the New Jersey Invasive Species Strike team, meaning they are not widespread throughout the state – although they may be concentrated in some specific locations.

One big concern about jumping worms is their ability to reproduce. Unlike most other earthworms, jumping worms are parthenogenic – they self-fertilize and don’t need mates to reproduce. Each new generation begins with the production of hardened egg capsules, known as cocoons, that overwinter in the soil to hatch the following spring. These cocoons are resistant to cold and drought and are too tiny to be easily seen.

What can you do to stop the spread of jumping worms? The University of New Hampshire offers the following advice:

• Do not buy or sell mulch, topsoil, compost, or plants that are infested with jumping worms. Before bringing these products home and introducing them to your landscape or garden, carefully inspect the materials for signs of jumping worms and their castings.
• Be especially careful when sharing plant material at community plant sales and swaps. Jumping worms will readily crawl in to reproduce within nursery pots. If you’ve seen jumping worms in your garden, avoid sharing plants with other gardeners.
• Before you purchase any new plants, take a close look at the potting soil. If jumping worms are present, you will see signs of their telltale, coffee-ground like castings on the soil surface. To make sure you aren’t introducing jumping worms with new plantings, try to remove most of the soil from the root ball of a new plant. Knock off the soil into a garbage bin and rinse the roots with water to remove any remaining soil.
• Jumping worms are occasionally sold as fishing bait or for use in vermicomposting. Do not purchase them for these purposes (or any other purpose), and do not release them into the garden.

Jumping worms are only one of many invasive animal species found in New Jersey. To learn more about New Jersey’s invasive animal and plant species, visit the New Jersey Invasive Species Strike Team website at www.fohvos.info/invasive-species-strike-team/. The strike team is a project of the nonprofit Friends of Hopewell Valley Open Space (FoHVOS).

And for information about preserving land and natural resources in New Jersey, visit the New Jersey Conservation Foundation website at www.njconservation.org or contact me at info@njconservation.org.