A jumping worm, Amynthas agrestis, is smaller than an earthworm. The key difference is in the collar, known as the clitellum, which is closer to the jumping worm’s head and appears smooth, rather than ribbed. (Photo courtesy New York Invasive Species Research Institute)

Editor’s note: Ed Robinson’s “Nature Notes” column runs on the Harpswell Heritage Land Trust’s website, hhltmaine.org. The Anchor is reprinting this column with permission from the Land Trust.

Just when it is safe to go outdoors without fear of browntail moth caterpillars or disease-bearing mosquitos, along comes more bad news. While this new pest will not harm you directly, it damages the environment around you, and if you are a gardener, there is no joy in this article. Even worse, this pest is well established in Maine and there are no natural predators here.

The troublemaker is a worm, which sounds innocuous. Worms have been welcome inhabitants of our gardens, breaking down organic debris, aerating the soil, and providing food for robins or weasels. This worm has flashy nicknames like jumping worm, snake worm or Alabama jumper, because they are highly active when disturbed. It is properly known as the Amynthas worm with several species, although they are difficult to identify. These worms originated in Eastern Asia, where there are natural predators to keep them in check.

I read about these worms several years ago, but they seemed a minor issue then. Originally found in a Maine greenhouse in 1899, scientists did not consider them established in Maine until 2014, when populations were discovered in commercial gardens in Augusta, Portland and Boothbay. Gardeners actively transplant soil materials and plants, thereby spreading pests such as jumping worms. I heard from three different Harpswell women in the last few weeks that their gardens were infested. (Thanks to them for sending me research materials.)

The glaciers of the Ice Age scoured the soils of New England and removed native worms. Earthworms and nightcrawlers in our lawns are also invasive species, imported along with plants by early European settlers. Worms in our lawns and gardens are generally benign or positive, but they can be destructive in forested areas, robbing the soil of nutrients vital to a wide range of species. Jumping worms take things to a new level because they reproduce rapidly and are active in the top 2 inches of soil.

Jumping worms have lasting effects on the environment by removing nutrients and leaving dry castings (poop) that cannot support plants, fungi or invertebrates. The decline of those species will cause a decline in the populations of vertebrates that depend on smaller species for food. Soil may also become more susceptible to erosion.

In commercial greenhouses, jumping worms have been found to reduce the performance of potting soils and to trigger drought-like conditions in plants. With our forests and native plants already under stress from climate change and other invasive species, we can ill afford an invasive species that causes soil degradation.

Several issues with these worms make controlling them nearly impossible. They can spread more quickly than other worms, becoming the dominant species. Adult worms prepare tiny cocoons in late summer or early autumn for the next generation. Those cocoons overwinter in the soil and hatch in spring. The cocoons are only 2 millimeters in size, making them nearly impossible to spot in soil and therefore easily transported from one garden to another. The worms can separate their tails when seized by a predator, allowing the worm to survive and continue its destructive behavior.

Gary Fish is Maine’s horticulturist, within the Department of Agriculture, Conservation and Forestry. For years he received 10 reports annually of jumping worms, but in 2022 that rose to 150 reports. Gary has more than 300 reports in 2023, and he believes jumping worms are established in at least 13 of Maine’s 16 counties.

There has been very little research on jumping worms to date, none of it within Maine. Broad control strategies might include heating soils to 104 degrees Fahrenheit, controlled burning, or spraying vermicides, but Gary feels those are impractical. While it is illegal to import jumping worms for bait or composting without a permit, there are effectively no controls on their spread. Gary plans to discontinue taking consumer reports next year.

What can a gardener do? Choose bare root saplings with no soil. Verify the source of transplants and ask hard questions about the possible presence of jumping worms or cocoons. Purchase soil products or compost in bags that have been heated as opposed to bulk shipments that may trigger an infestation. Make sure gardening tools are cleaned carefully with hot water and soap, catching the soil in a bucket and allowing it to dry in hot sunshine. If you find live jumping worms in soil, place them in your garbage, ideally dead.

If you find jumping worms in your own garden, please avoid passing them on to others.