Update on Jumping Worms in Minnesota

A recent article about jumping worms in the StarTribune by regular Northern Gardener contributor Gail Hudson has brought more attention to this new invasive pest and its affect on home gardeners. Here's what we know so far, with links to additional sources of information.

What are jumping worms?

Jumping worms are members of the genus Amynthas. They are native to Japan and Korea, and were first discovered in Minnesota by Lee Frelich of the University of Minnesota in 2006. They get their name from their tendency to jump around when disturbed. (Check out our post from last year for a video of them in action.)  They resemble other earthworms (also not native to Minnesota) but have a notable smooth, light-colored ring around their bodies. What makes them distinctive is the jumping and the destruction they can inflict on soil.

jumping worms in strawJumping worms live in leaf litter or the first few inches of soil. They survive our winters as  cocoons underground. Worms are very tiny in spring but grow to 4 to 5 inches by midsummer. As they infest an area, the soil begins to look like coffee grounds or ground hamburger. Serious infestations can lead to soil erosion, especially on slopes, and damage to plant roots and beneficial soil fungi and microbes. Jumping worms are also a danger to Minnesota forests, which is why the Department of Natural Resources has declared them a terrestrial invasive.

Where are they in Minnesota?

Jumping worms were first found in Loring Park in Minneapolis by Dr. Frelich in 2006. In 2007, he also found them on the St. Paul campus at the University of Minnesota. Since then, they have been found throughout the Twin Cities, in Rochester and parts of southeastern Minnesota, and possibly in Duluth. The university is conducting a research project later this year to find out how far the worms have spread in Minnesota and is currently looking for volunteers to help with the project. So far, outside of the Twin Cities, the number of worm reports are fairly small.

What should gardeners do?

Jumping worms move around in compost, mulch and potted plants, and the best way to control this pest is to prevent their spread.  Frelich recommends against using leaf litter as mulch since it's so attractive to the worms. The DNR suggests gardeners remain vigilant and do the following:

  • Check in your garden and in any plants you bring into your garden for soil that looks like coffee grounds or has very jumpy worms in it. Also check compost and mulch and make sure they are from reputable sources. (The article in the StarTribune notes that no commercial growers or garden centers have reported a jumping worm infestation and most commercial operations use a peat soil mix that is not attractive to the worms. So, buying plants from a garden center should be safe.)
  • If you believe you have jumping worms, do not move any soil or compost from your site. Contact the DNR and send them photos or videos of the worm.
  • Clean soil off your tools if you are taking them to and from another garden, such as a community garden, to avoid spreading worms or eggs accidentally.
  • Know exactly what you are buying, if you buy worms for composting.
  • Buy bare root plants when possible, or grow your own from seed.
  • Plant sale protocols including checking the soil for the coffee ground appearance and, if possible, removing soil and transporting the plants as bare roots or repotting them in a sterile soil mix. The university has a list of recommendations for garden clubs and other groups sponsoring plant sales.

If you'd like to read more about jumping worms, how they got here and how scientists are dealing with them, Atlantic magazine has a great article about the issue.

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