Jumping worms are another invasive pest we can add to that growing list, which includes dozens of fish, insects, and plants, both dryland and aquatic. The first known discovery and identification of these worms happened in Wisconsin in 2013. In Illinois, they were first reported in 2015 in Cook and DuPage Counties, and have continued to spread into surrounding counties.
In 2017, there were confirmed reports in 10 counties. As of October 2019, that grew to six northern Illinois counties, two central Illinois counties and eight counties in southern Illinois. The pest also is suspected in eight additional counties throughout the state.
These worms, which are native to East Asia, are known by a number of names across the United States, including crazy worms, Asian jumping worms, Alabama jumpers and snake worms. When disturbed, the worms will literally jump about like in this WGN TV segment featuring Extension’s Chris Evans. They are about 4 to 8 inches long, darker on top and have a smooth, milky white band, called the clitellum.
Jumping worms have the potential to change the soil structure, deplete available nutrients, damage plant roots, and alter water-holding capacity of the soil. This is especially a concern in our forests, where organic matter is limited. Unfortunately, populations of jumping worms can be found that are 10 times higher than our native worms, and these invasive pests can consume great amounts of soil when concentrated in a single area. The altered soil, often the top 3 to 4 inches, will look like coffee grounds.
The first part of “good news” here is that adult jumping worms are not winter hardy and die relatively soon after our soils get cold. That was the good news. The bad news is they produce nearly microscopic cocoons containing eggs that are winter hardy. Additionally, the jumping worms are parthenogenic, meaning they do not have to mate in order to create those cocoons with eggs inside!
While you should never say never, gardeners are not going to get jumping worms when purchasing plants from a garden center (another piece of good news). The potting soils used for our annuals and perennials are created with growing media that typically has been pasteurized to control disease organisms with temperatures high enough to control any insects and insect eggs, including earthworms too. More good news, the purchase of any kind of organic matter amendments that have been pasteurized or composted (where temperatures will reach 140 degrees) will not contain viable eggs.
How do we manage jumping worms? The adult worm is the one generating the overwintering cocoons, so when you find them, removal is the best option. Birds do not like to eat them as they are too slimy and do not taste good. (I can confirm the slimy part, not so much how they taste.) You can place them in a plastic bag and they will die very quickly, and then throw them out with the trash. There have been studies showing the eggs will die at 104 degrees, but that is not practical for us gardeners. Your best bet is to focus on managing the adults until research tells us more.
For more information on identifying these worms, visit https://extension.illinois.edu/dkk/horticulture. If you suspect you have a population of jumping worms, please contact me at firstname.lastname@example.org or 630-584-6166, or the University of Illinois Plant Clinic at email@example.com or 217-333-0519.