Lisa Johnson, Dane Co. UW-Extension Horticulture Educator
As you are doing yard clean-up this fall, there is yet another new invasive pest to look for, identified in Dane County in October of 2013. Jumping worms (Amynthas spp.) are of Southeast Asian origin and they can be very damaging to soil structure in gardens as well as forest environments. No earthworms are native to Wisconsin—they were all killed off during the Ice Age. We do have 20 European species in the state, however. Earthworms all have negative effects on the forest duff or litter layer, which acts as a protective cover and helps forest floors to retain moisture, insulate tree roots, provide nutrients, prevent erosion, etc. When that litter is eaten by earthworms, the protective cover is removed, exposing the soil and causing erosion, compaction and increased runoff. This disturbance favors the spread of invasive plants such as garlic mustard and buckthorn. Researchers have also documented the negative effects of earthworms on forest regeneration and ground nesting bird populations.
The jumping worm is especially destructive since it lives right in the duff layer rather than lower in the soil profile. Jumping worms tend to outcompete European earthworms to become the only species in forest environments. They consume the layer of leaves and other organic matter on top of the soil faster than other earthworm species. They have been found in Dane, Sheboygan, Jefferson, Waukesha, Milwaukee and Racine counties, and signs of the worms (though no adults) have been noted in 8 other counties. Jumping worms have also been found in some states in the Eastern U.S. We don’t know how long they have been here in Wisconsin, but introduction through contaminated soils or plants is suspected. Since they can spread very quickly, it is important to slow the spread. Best management practices are being developed by the DNR and municipalities. Don’t share plant divisions from your garden or soil if you know you have jumping worms.
Jumping worms are parthenogenetic, producing eggs without the need for a mate, so just one worm can start a new population. Their eggs survive as microscopic cocoons over winter, with all the adults dying in fall. You won’t see the young worms until late June each year, but you will see the ‘soil signature’ from their feeding during the previous season. Jumping worms feed on soil organic matter, leaf litter and mulch and create very grainy-looking and hard little pellets when they excrete. The excretions resemble coffee grounds, and have poor structure for plants to grow in. Also, the worms’ feeding removes the organic matter that plants, fungi and bacteria need for nutrients. Adult jumping worms are 3 to 5 inches long but can grow to up to 7 inches in length. Jumping worms resemble regular earthworms but there are some important differences. Unlike European earthworms, they don’t produce slime and are more gray or brown in color than pink. Their clitellum, the band of lighter-colored tissue near the head, is smooth, not raised like other earthworms and whitish, not pink. It also goes all the way around the body, not just partway, like the European worms. The body is more rigid as well. Jumping worms get their name from their behavior—when handled, they thrash violently, may jump into the air or even shed their tails. They move in a serpentine fashion like snakes, as well. Check out this video to observe them moving. After hatching in late June, each worm begins reproducing; their life cycle lasts 60 days, so we can have two generations easily each year. Unfortunately, other than killing any worms you find by placing them in a closed plastic bag in the sun, there are no products labeled to kill them, since soil drenches would also kill beneficial soil organisms. Some products are being tested, but I haven’t heard about any results as of yet.
To report a sighting of jumping worms, email Invasive.Species@wi.gov . For more information and to see photos, visit http://dnr.wi.gov/ and search for the keyword ‘jumping worm’. There is also a great article in Wisconsin Natural Resources that you may want to check out .
Editor’s note: these worms have also been identified in Outagamie County.