Ear to the Ground: The Insider Dirt to Gardening in Upstate NY

Asian Worms

by janem on September 6, 2018

by Walt Nelson

Mature jumping worm, with characteristic milky white clitellum (band near the head of the worm). Photo by Susan Day / UW- Madison Arboretum

Earthworms, good in the garden, right? Maybe, but not in our natural landscapes. Earthworms have
not been native to our temperate zone since the last ice age. Our forest and landscape ecosystems have evolved without them.

European colonists inadvertently brought their native worms (Amynthas spp. and Metaphire sp.) to North America. Those worms colonized much of the area and have had an adverse impact on the soil ecology. But even more recently introduced worms are wreaking havoc in
the forest and landscape.

Asian worms were accidently introduced to southern Appalachia in the late 1880s. They migrated via human activity to the upper Midwest, New England, the Northwest, and the Northeast, including many areas of upstate New York.

The three species in the two genera are visually indistinguishable. Their cloudy, white-to-gray smooth clitellum differentiates them from European worms, which have a raised pink to dark-red band.

The Asian worms move in a snakelike fashion, rather than compress and stretch as do the European worms. When disturbed they thrash about, jumping or moving in an erratic manner, hence some of their common names, which include Alabama jumper, crazy worm, Asian jumping worm, and snake worm.

Their preferred habitat is the top two inches of soil or within leaf litter or mulch. The poop, or castings, of the Asian worms is courser, almost granular, in comparison to European worm castings. Organic duff degrades to their castings in a single season. All worms consume organic
matter, releasing the nutrients previously tied to the organic matter. However, the faster nutrient release by Asian worms results in a soil environment less suitable for native plants and microbes that are dependent on partially decomposed organic matter.

Asian worms are parthenogenetic, requiring no mate for reproduction. Adults die as winter approaches, but their cocoons, containing one or two eggs, survive the winter and hatch in April. These young feed, grow, and reproduce during the growing season.

There are no registered pesticides for use against any worms. Researchers and gardeners have attempted to manage the Asian worm with diatomaceous earth, sulfur, or mustard. The results are erratic and inconclusive. Best management practices in minimizing their spread when moving plants from areas where the Asian worm is present includes washing roots and removing both adults and cocoons. Plant these bare root plants in a “peat-lite”—type medium. If keeping these potted plants outdoors, avoid ground contact to prevent worms from migrating up into the pots.

Census for the presence of worms in soil by drenching a one-square-foot area with one gallon of a ground mustard solution (1 gallon of water, 1/3 cup ground yellow mustard) and count the worms that will appear at the surface.

Practically, the “cat may be out of the bag” with the Asian worm. That said, best management practices can slow their spread. Research is underway in New York and elsewhere to help us learn more about these worms and hopefully provide solutions for their management.

Walt Nelson is a horticulturist with Cornell Cooperative Extension, Monroe County.

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