Do you remember when we learned that there were no native earthworms in Minnesota and we were alerted to the damage being done by non-native angle worms in our hardwood forests? Well, there’s another new worm in town that poses an even greater threat to our beautiful Minnesota ecosystems — the invasive Asian jumping earthworm.

Jumping worms have been present in the horticulture industry in the northeast U.S. since the 1940s and have now made their way to some Midwest hardwood forests, parks, arboretums, nurseries, municipal compost sites and home gardens.

The three jumping worm species of greatest concern in the U.S. are Amynthas agrestis, Amynthas tokioensis and Metaphire hilgendorfi, which are all native to Southeast Asia. These species frequently co-invade ecosystems and cause significant damage.

Forest floors normally have a thick blanket of duff created from decades of slowly decomposing leaves. The duff layer creates a home for insects, amphibians, birds and native wildflowers.

Lady’s slipper lost

When the jumping worms move in they devour the decomposing layer in a short time. All of the nutrients that have been stored up over time are released in one giant burst, too quickly for most plants to capture. Without cover, the invertebrate population in the soil collapses and the depleted bare soil no longer supports germination of trees and understory plants. Plants like trillium, lady’s slipper, bellwort and other woodland ephemerals are lost because the duff is gone and the networks of symbiotic fungi that many native plants depend on are destroyed.

In gardens and parks jumping worms inhabit the interface between mulch and topsoil or within the top 2 to 4 inches of soil. They can often be detected in a garden by pulling away a few square feet of mulch.

Jumping worms will alter garden soil by stripping it of organic material and changing the soil structure so that it becomes grainy like coffee grounds, making it difficult for plants and seedlings to stay anchored. This disturbed soil dries out quickly, erodes easily and generally makes poor habitat for plants.

Some people report the remarkably rapid decomposition of woody mulches in the presence of jumping worms. They apparently have a lignin-eating enzyme called peroxidase which allows them to eat fibers of wood mulch.



In a pa

Jumping worm castings look similar to coffee grounds. Beth Solie / Olmsted County Master Gardener
Jumping worm castings look similar to coffee grounds. Beth Solie / Olmsted County Master Gardener
per written by Lee Frelich, University of Minnesota Forest Ecology director, he describes how a swarm of jumping worms destroyed a garden bed of hosta and other plants in Loring Park in Minneapolis. Upon examination of the wilted hosta, Lee was surprised to find that they were scarcely attached to the soil. The worms had turned the soil into pellets like coarse cat litter and when he stuck his finger in the soil the worms jumped in every direction. Populations of jumping worms can become very large, coupled with swarming behavior, in some areas.

Annual species

Amynthas species were nicknamed jumping worms due to their energetic thrashing if disturbed. They jump out of your hand if you are holding them and may shed their tail allowing the front end of the worm a 50% chance of escape.

They grow 6 to 8 inches long and appear denser, almost hard, compared with regular earthworms. Some have a bluish sheen, like oil on water. They have a more turgid and muscular appearance than night crawlers because they retain high levels of salt as protection against predators.

Jumping worms are annual earthworms in our climate, which means they will die with the first hard frost. Unfortunately, before they die each worm will lay dozens of winter-hardy cocoons that ensure persistence of the population through the following season.

The cocoons hatch in the spring when ground temperatures reach about 50 degrees. Once hatched these worms require 60-90 days to reach maturity and begin producing cocoons. When the worms are mature they will have a whitish band called the clitellum going all around their body near the head end of the worm. This is where the cocoons are produced.

Report infestations

Cocoons and young worms are difficult to detect. Most infestations of jumping worms are found under mulch or composting leaves in mid to late summer when the worms are large and causing the most damage.

You can also check your property for jumping worms by using a mustard pour (won’t harm plants). Mix one gallon of water with a third cup of ground yellow mustard seed and pour slowly into the soil in a 1 foot square area. This will drive any worms to the surface.

Report new occurrences of jumping worms to the Minnesota Department of Natural Resources by contacting laura.vanriper@state.mn.us or log in and submit a report through EDDMapS Midwest (www.eddmaps.org/midwest).

If you have jumping worms. avoid moving plants or other organic material from your yard. Pick up any jumping worms that you find, put them in a zip plastic baggie and put the baggie into the garbage.

The worms and their cocoons are spread very easily in leaves, soil, sod, mulch, compost and potted landscape plants, on boots and shoes, in fishing bait and by gardeners sharing plants. Since cocoons are only 2 mm in diameter, similar to a grain of soil, they can easily go unnoticed and be inadvertently transported from one area to another. Spread is often associated with wood mulch coming from all sources including bagged mulch.