an adult invasive earthworm

Invasive jumping worm (Amynthas sp.). Photo: Susan Day / UW–Madison Arboretum

Updated: November 16, 2021

Key points

  • “Jumping worms” encompass three similar-looking non-native, invasive species.

  • The worms thrash wildly and move in a snake-like manner; their feeding produces granular castings that look like coffee grounds on the soil surface.

  • They change soil composition, making it drier and depleted of nutrients, which limits normal plant germination and growth.

  • The best way to manage jumping worms is by prevention (e.g, don’t purchase for bait or vermicomposting) and physical removal if they are detected. There are no chemical controls.

What are invasive jumping worms?

  • Worms referred to as jumping worms, crazy worms, snake worms, Jersey wigglers, Georgia jumpers, and Alabama jumpers include three similar-looking species: Amynthas tokioensis, Amynthas agrestis, and Metaphire hilgendorfi, all of which are in the family Megascolecidae. Two or three species often occur in the same location.

  • They are all non-native species, originating from Asia.

  • They have an annual life cycle; the adults die after the first hard frost; the next generation survives the winter in the form of cocoons (egg casings). They hatch in the spring when the soil temperature is consistently about 50˚F. They develop into full-size adults in about 60 days. Climate change may be increasing the number of generations to two per year.

  • Individual worms can reproduce without a mate (parthenogenesis) and their populations can increase quickly. They displace and out-compete other earthworms.

  • They live only at the surface level of the soil and leaf litter (epi-endogeic) and therefore do not help gardeners with deep soil aeration, nutrient movement, or water infiltration.

  • They can digest wood and favor areas with leaf mulch; areas with pine needles and native grasses are less attractive to them (source: University of Wisconsin-Madison).

side by side comparison of invasive earthworms
Two different species of invasive jumping worms showing size variation. The worm on the left is likely not fully mature as the clitellum is not pale. Photo: Marie Johnston/ UW–Madison Arboretum

Where are they in Maryland?

  • Jumping worms have been in the eastern United States for decades. Amynthas agrestis was first recorded in 1939 in Baltimore, Maryland (source: Chang 2016). The extent of their current distribution in Maryland is unknown.

  • They are moved by way of human and animal activities -- most likely in the cocoon stage which is difficult to detect. They spread into new areas by way of mulches, compost, and potted plants; in soil on tools, equipment, and shoes; and in soil runoff.

Why are they a problem?

  • Invasive jumping worms consume large amounts of organic matter and change surface soil composition. They make the soil more gravelly in structure, drier, more prone to erosion, and less favorable to normal soil microorganisms (fungi, bacteria), and plant growth. The worm castings (feces) sit on top of the soil, leaving nutrients out of reach of plant roots and increasing the risk of nutrient runoff.

  • Any organism that relies on the normal composition of a natural forest floor for food and/or habitat will be disrupted by invasive jumping worms. This includes native plants, insects, birds, and other animals. A forest floor depleted of its normal mulch layer is less hospitable for seed germination and native plant establishment.

  • In a home garden, soil disruption from jumping worms can diminish the growth of annuals, perennials, and turfgrass.

soil like coffee grounds is a symptom of invasive earthworms
The image above shows the boundary of an area invaded by Amynthas jumping worms, with the jumping worm’s granular “soil signature” on the left and uninvaded soil on the right. Photo: Susan Day / UW–Madison Arboretum

How to prevent invasive jumping worms

  • Avoid using compost and mulch of unknown origin. When purchasing bulk compost and mulch, find out if the material was heat-treated 131˚F for at least three days (sources: Cornell University, Penn State University). Alternatively, make your own compost and retain fallen leaves on your property to use for mulch/compost.

  • Inspect plant pots for granular-looking soil before bringing plants home. Purchase bare-root plants, if possible. 

  • Be careful about bringing soil onto your property on tools, shoes, and plants; require landscape contractors to use clean equipment.

  • Do not purchase invasive jumping worms for bait or vermicomposting. Do not dispose of unused bait on the ground or in or near the water.

How to determine if you have invasive jumping worms?

  • The presence of distinctive granular soil that looks like spent coffee grounds or ground meat may be your first indicator of jumping worms. This granular material is mostly worm castings.

  • Worms present in leaf litter and mulch or very near the soil surface range from about 1.5 to 8 inches in length (varies by species and maturity). They are easier to identify from June through late summer when they are mature.

  • They jump and thrash wildly when handled. Their movement is snake-like. They sometimes drop a few segments of their tail when aggravated.

  • They are smooth, gray/brown/purple, have a metallic sheen, rigid texture, dark pigmentation on the top side, lighter on the bottom.

  • A circular band (clitellum) completely encircles the body, lies flat against the body rather than raised, and looks cream-colored or milky white on mature worms. The clitellum is relatively close to the head, at segments 14-16. (source: Chang, 2016)

  • Cocoons are 1-3 millimeters in diameter and resemble a particle of soil.

  • Mustard test: Using a liquid “mustard pour” is a way to test for jumping worms. Mix ⅓ cup of ground yellow mustard seed into 1 gallon of water and pour half of the liquid slowly over a 1 square foot of soil you want to test. Wait a few minutes and pour the rest. This will make worms (any earthworms) come to the surface. Identify, collect, and discard jumping worms, if present. The mustard solution will not harm plants.

student pours mustard water solution on the ground to test for invasive worms
Student Mark Garcia conducts a mustard pour to sample for invasive jumping worms. Photo: Annise Dobson
The snakelike movement of a jumping worm (Amynthas spp.). Video: Carly Ziter, courtesy UW– Madison Arboretum

What to do if you find invasive jumping worms?

  • There are currently no chemical control methods for invasive jumping worms.

  • Physical removal methods:

    • Hand-pick worms, seal them in a trash bag and discard the bag in your trash.

    • Worms also can be killed in vinegar or rubbing alcohol (source: Cornell University).

    • Spread bulk mulch/compost on a driveway to expose worms to predators and hand-picking.

    • The cocoons are sensitive to heat. Research has shown that the cocoons are killed at a temperature of 104˚F for three days (source: University of Wisconsin). Placing a clear plastic tarp over soil or mulch (solarization) can increase the temperature. However, this may not generate enough sustained heat to a depth that will kill these organisms, so this is not a reliable method of control. 

    • For plant exchanges and sales: 

      • Do not share plants in potted soil from your garden if you know you have jumping worms.  

      • When the presence of jumping worms/cocoons is unknown, as a precautionary measure, plants can be bare-rooted and potted into sterile potting medium prior to exchanges or sales. The University of New Hampshire Extension explains these procedures.

      • Educate others about jumping worms and good practices to prevent their spread.

  • The Maryland Department of Agriculture and the Maryland Department of Natural Resources are not currently regulating invasive jumping worms. You can report invasive jumping worms and submit your photos on the Early Detection and Distribution Mapping System, https://www.eddmaps.org/.

  • Research is underway to explore the use of various products and methods (e.g., fungi, saponins, sulfur, fire, biochar) to control invasive jumping worms.

Additional resources

The visible invisible: impacts of invasive jumping worms | Maryland Invasive Species Council, 2019

Asian jumping worms: a homeowner's guide | Cornell University JWORM Working Group, 2021

Asian jumping worms: a threat to gardens and woodlands (has good close-up photos) | Ohio State University, 2020

Plant sales and jumping worms | University of New Hampshire Cooperative Extension

References 

Asian jumping worms: a threat to gardens and woodlands, Ohio State University, 2020

Chang, Chih-Han; A guide to identifying the Asian earthworms Amynthas agrestis, Amynthas tokioensis, and Metaphire hilgendorfi, 2017

Chang, Chih-Han et. al.; Asian pheretimoid earthworms in North America north of Mexico: An illustrated key to the genera Amynthas, Zootaxa, December 2016

Chang, Chih-Han, et. al; Co-invasion of three Asian earthworms, Metaphire hilgendorfi, Amynthas agrestis and Amynthas tokioensis in the USA, Biological Invasions, October 2017

Dobson, Annise; The visible invisible: impacts of invasive jumping worms, Maryland Invasive Species Council, November 2019

Hamilton, Eric; Heat kills invasive jumping worm cocoons, could help limit spread | University of Wisconsin-Madison, 2019

Herrick, Brad. Invasive jumping worms seminar, 2020 https://pbswisconsin.org/watch/university-place/invasive-jumping-worms-mj8j7h/

Lamp’l, Joe; 211 Invasive Asian jumping worms: what gardeners need to know (interview with Brad Herrick, University of Wisconsin), June 2021

Look out for jumping earthworms | Penn State University, August 2018

Plant sales and jumping worms: University of New Hampshire Cooperative Extension, 2020

Author: Christa Carignan, Coordinator, Home & Garden Information Center, University of Maryland Extension. 2021