Asian earthworms belonging to the genus Amynthas, commonly known as jumping worms, are causing significant concern across North American landscapes. These species are characterized by their aggressive, snake-like thrashing movement when disturbed, earning them nicknames like “crazy worms” or “snake worms.” Unlike other earthworms that burrow deep, jumping worms live in the top few inches of soil, voraciously consuming the leaf litter and organic material. This intense feeding activity quickly transforms the soil structure into dry, granular pellets resembling coffee grounds, which limits plant germination, increases erosion, and depletes nutrients for native flora.
The Challenge of Predation
Jumping worms possess a suite of biological defenses that make them challenging targets for native predators. When handled or disturbed, they exhibit a frantic, thrashing, and “jumping” movement, which can startle or deter an unfamiliar animal. Their skin texture is notably different from that of native earthworms, being smooth, glossy, and firm, rather than slimy.
These physical traits are coupled with chemical defenses. When agitated, the worms may secrete a yellow-tinged mucus, acting as a chemical repellent to discourage consumption. As a final defense mechanism, a worm may shed its tail segment, which continues to writhe, allowing the rest of the body to escape. These combined traits often lead native animals to avoid or quickly reject the worms after an initial attempt at feeding.
Documented Natural Enemies
While jumping worms are not easily incorporated into the diet of native fauna, some animals have been observed consuming them opportunistically. Ground-feeding birds, such as American Robins and wild turkeys, may prey on the worms as they forage near the soil surface. These birds are generalist feeders and will attempt to eat whatever soft-bodied prey they encounter.
Small, ground-dwelling mammals also interact with the worms while digging through the topsoil layer. Predators documented to consume jumping worms include:
- Moles
- Shrews
- Raccoons
- Skunks
- Various snake species
Invertebrate predators, including centipedes and ground beetles, may also attack the worms, especially smaller juveniles. Beyond direct predation, biological agents pose a threat, such as the entomopathogenic fungi Beauveria bassiana and Metarhizium brunneum. Certain nematodes are also being investigated for their potential to infect and control these invasive worms.
Limited Efficacy of Biological Control
Despite the documented natural enemies, biological control methods have proven largely ineffective in managing jumping worm populations. A significant factor is predator preference, as many native animals find the worms unappealing or difficult to handle. Observational reports indicate that many birds and amphibians will spit out the worms, preferring less aggressive, native earthworm species.
The primary limitation is the reproductive cycle and resilience of the worms’ cocoons. Adults die off with the first hard frost, but they leave behind microscopic, extremely durable egg casings that overwinter in the soil. Since each worm can reproduce asexually, a single individual can start a massive new infestation.
These cocoons are highly resistant to predation and survive harsh winter temperatures, establishing a persistent “cocoon bank” in the soil. When soil temperatures consistently reach about 50°F in the spring, the juveniles hatch, ensuring rapid re-infestation. This high reproductive capacity and the durability of the egg stage overwhelm any localized control offered by native predators.
Non-Predatory Management Strategies
Since natural predators provide little population control, management of jumping worms relies heavily on human intervention and prevention. To stop their spread, never move soil, mulch, compost, or potted plants from infested areas to uninfested ones. Gardeners should always clean soil and debris from tools, equipment, and footwear after working in a potentially contaminated area.
A direct method for controlling the worms is manual removal. When jumping worms are found, they should be collected and placed into a sealed plastic bag left in the sun for at least a day. This solarization process heats the contents to over 150°F, which is sufficient to kill both the worms and their cocoons before disposal.
To detect and collect the worms easily, a mustard solution can be poured over the soil, which irritates the worms and forces them to the surface. For treating bulk materials like mulch or compost before use, solarization is an effective approach. Maintaining the material at or above 104°F for a minimum of three days will destroy any cocoons present.