Jumping Worms Spell Bad News for Gardeners

For those of us passionate about gardening, or even broader concepts like forest conservation, earthworms have long been thought of as a good thing. Earthworms are an essential part of soil management, helping to take nutrients from the surface and bring them down below the surface.

Unfortunately, not all earthworms are created equal–especially when outside the habitat they are meant for. Jumping worms, named for their violent thrashing when handled, are native to Japan and Korea. There they co-exist peacefully in their native ecosytem and cause no harm. It’s another story when they are transplanted somewhere else.

A shallow problem

Jumping worms become a problem when they end up somewhere they’re not supposed to be. Unlike other species of earthworm which take nutrients from the surface and dive deep down with it, jumping worms stay at the top of the soil and vigorously churn that surface into a coffee-ground like consistency.

This churning changes the soil structure, making the soil less able to retain moisture and air, while also keeping the nutrition from decaying plant matter on the surface instead of taking it down below like normal worms do.

At best, this robs nutrition from plants and trees who can’t access this nutrition so close to the surface. At worst, it can change entire ecosystems. In some locations, such as in Iowa, earthworms aren’t native at all. At some point in the last 10,000 years, it is believed that an iceberg killed what native populations were there.

The forest since then has grown up and evolved to life without earthworms–a big problem when they’re suddenly reintroduced, and with a species not good for soil to begin with.

How Jumping Worms Invaded

No one knows the precise moment that jumping worms made it from Japan or Korea to the US. Part of the problem is that jumping worms can leave their egg sacks behind in compost and other amendments, cling to tires and feet, and spread almost invisibly.

It’s also possible that they were brought in used as fishing bait, although their characteristic thrashing frequently means falling off the hook. Worms discarded by the side of a lake after fishing can quickly spread, if not by their own movements than hitching a ride.

Unfortunately, once an infestation is set in there’s not much that can be done. They spread very rapidly, and can cause severe damage once set in.

Gardeners can test their soil by making a simple concoction of 1/3 of a cup of powdered mustard and a gallon of water. Pour this in a test area. The mustard irritates worms that live just under the surface, such as the jumping worm.

If any worms come to the surface and start violently thrashing, these are probably jumping worms. It’s best to kill them and throw them away. Any jumping worm you kill will help stop the spread. Even if your home and garden are never back to normal, you can slow down the spread until researchers come up with better solutions.