Invasive Jumping Worms

About jumping worms

• “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, make compost at home, inspect potted plants, buy bare-root plants) 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 and survive 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. They have “boom” and “bust” cycles from year to 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).

Where are jumping worms 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. They like wet (not saturated) soil and get transported along streams and rivers.

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.

How to prevent invasive jumping worms

• Make your own compost and retain fallen leaves on your property to use for mulch/compost.

• If purchasing bulk compost and mulch, jumping worms and cocoons do not survive heat-treatment over 105F. However, even with heat treatment, jumping worms can infest compost piles or mulches if they are stored where jumping worms are present and the temperature is suitable for their survival.    

• If you buy compost in bags, put the bags in the sun for several days to heat up. (Depending on the time of year/temperature, this may not be sufficient to heat to 105F.)

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

• 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 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 rigid texture, dark pigmentation on the top side, lighter on the bottom. They are iridescent when fully mature.

• Adult jumping worms have a cream-colored band (clitellum) that completely encircles the body. The clitellum lies flat against the body for most of the adult stage, except during egg production when it swells. The clitellum is relatively close to the head, at segments 14-16. (source: Chang, 2016). In contrast, on European earthworms, the clitellum is saddle-shaped and does not wrap around the entire body.

• 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 hot yellow mustard seed (look for Chinese or Asian hot mustard) 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 or kill the worms.

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 by putting them into a container with vinegar or rubbing alcohol. Dead worms can be composted.
  • Spread bulk mulch/compost/soil on a driveway to expose worms to predators and hand-picking. This will not kill any cocoons that are present.
  • Solarization: Jumping worm adults and cocoons will not survive over 105F. One method to kill them is to make a “solarization package.” Lay down a sheet of clear plastic (e.g., painter’s drop cloth) in a sunny area, 10-15 feet in length, place compost, mulch, or soil on top of the plastic, no deeper than 6-8 inches, and then wrap the plastic over top and around to encase the material completely in a plastic package. On a sunny summer day, research has shown a solarization package can heat to over 150F. (Görres, University of Vermont). However, the temperature will vary by time of year and local conditions. Research on the amount of time it takes to kill cocoons has varied and may take up to three days.
  • Solarization of garden soil is more difficult because the killing temperature of 105F cannot be maintained. Worms under the plastic will move to a different location.
     

• 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.

Ongoing research

• Research is underway to explore the use of various products and methods (e.g., fungi, saponins, sulfur, fire, biochar) to control invasive jumping worms. 
• Some native plant species have shown more tolerance to jumping worm invaded areas than others: Christmas fern, Jack-in-the-pulpit, and trout lily. 

Reporting

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/.

Additional resources

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

Invasive Jumping Worms Frequently Asked Questions | University of Massachusetts | Amherst

Jumping worms: identification | University of Massachusetts Amherst

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

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

Author: Christa Carignan, Horticulturist & Coordinator, Home & Garden Information Center, University of Maryland Extension. 2021. Rev. 2022.

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