Jumping worms (Amynthas spp.) are a relatively new and very troublesome invasive species posing a threat to trees and shrubs in the landscape in the United States. Unlike most earthworms, jumping worms live in the top few inches of soil, can survive in surprisingly and troublesomely dense populations and eat great quantities of organic material, including leaves, mulch and even plants. This can be especially challenging for lawns and gardens, but also for newly planted trees and shrubs.
Invasive earthworms, including jumping worms, are ecosystem engineers. They change soil characteristics that impact the types of plants that grow, upsetting the ecosystem of the insects and small animals present. Earthworms, including jumping worms, quickly eat the leaf litter on the forest floor. This leads to more exposed mineral soil, which is better for some invasive plants, including buckthorn, to germinate in. So these worms impact the whole ecosystem, increasing allergies and Lyme disease, reducing crop and forest productivity, reducing forest biodiversity and increasing the establishment of other invasives.1
Jumping worms are native to Asia. It is uncertain how or when they arrived in the U.S., or how widespread they are. Researchers suspect they’re underreported. iMapInvasives (imapinvasives.org) has the best data for the East Coast; EDDMapS (eddmaps.org) has the best information for Minnesota.
Identification
Jumping worms get their name because their movement is very jumpy when disturbed, often startling gardeners. However, for this article and in most publications, jumping worms actually represent a suite of non-native earthworms mostly in the scientific genus Amynthas, but a few are in the Metphire or Perionyx genera.
There are many confusing, sometimes colloquial, names for these worms. In an effort to standardize jumping-worm names, and to reduce the negative impacts some invasive species’ common names have on minority or marginalized human audiences, an effort is underway to give or improve common names for 12 jumping-worm species and groups. That effort is almost complete, but those names are not yet being publicized until better ways to identify between the species are clarified.
Jumping worms can only dependably be identified once the worms reach adult size. That may be in July in the Upper Midwest or earlier in more southern locales. To identify jumping worms, look for coffee-ground-type soil and look under leaf litter for very active, wiggling worms, varying from 1-1/2 to 8 inches or more in length.
They are similar in size to other earthworms, such as nightcrawlers or some of the larger angle worms, but their clitellum (collar-like ring) and coloring are different. On jumping worms, the clitellum is cloudy-white and constricted, unlike the swelled, saddle-like clitellum of nightcrawlers. On jumping worms, the clitellum wraps all the way around the body and is much closer to the head (11 to 13 segments) than that of nightcrawler worms, which are about the same size and often found deeper in the soil.
Hardly any home gardeners or natural-resource professionals and only a few worm experts can tell these worms apart to species. Some worms can only be identified to species after dissection or genetic testing. However, the most common of these jumping worms share the common identification criteria mentioned here, and cause very similar impacts to the environment.
Jumping worms live their whole lives in the first few inches of leaf litter and soil. They often move across the ground in an “S” pattern like a snake.
Jumping worms live for only one growing season. Eggs laid during the previous growing season hatch in late spring in 1 to 4 inches of soil. The worms grow during the summer, and the adults start laying eggs in August. Jumping-worm eggs are enclosed in small cocoons that are easily spread when fall leaves are raked and transported.
Prevention and management
There are no research-based control options for jumping worms, so preventing their introduction and reducing their spread are the only two management options currently available.
Jumping worms can digest cellulose, a key component of wood chips, and thus survive and thrive in wood-mulch piles and in bagged mulch sold at retail stores. Jumping worms seem to prefer wood-mulch landscape borders, causing the mulch to degrade more quickly and allowing the jumping worms to thrive in rich, moist topsoil. It’s important to monitor mulch piles and the soil around them for jumping worms to prevent jumping-worm spread through mulch distribution. Further, jumping worms can move surprisingly far across paved lots to get to wood-mulch piles.
Operations that cut trees and limbs and immediately chip them into a chip van and deliver them to the end users are unlikely to transport jumping worms. Jumping worms do not live in standing trees. Wood material that does not touch the ground will provide little opportunity for jumping-worm infestation.
While most prevention measures focus on avoiding the spread of jumping worms, heat-treating materials to kill jumping worms is one option. A study showed jumping worms die when held at 85 F (29 C) for three days. The study also found that jumping-worm eggs die when held at 104 F (40 C) for three days.2
Juvenile and adult worms can move around, so the worms may move to places within the mulch pile where the temperature is lower. Exact temperatures that kill worms and their eggs can vary depending on soil moisture and other factors. The study did not look at shorter periods of heat exposure.
The most reliable way to avoid the spread of jumping worms is to refuse to accept plants or other material from a yard, garden or other source known to have jumping worms or that is not actively working to prevent the spread of jumping worms.
It’s important to spread the word about jumping worms, their identification and the need for proper reporting. Though a few states have a reporting system for jumping worms, the two most common are the sources mentioned previously, EDDMapS and iMapInvasives.
References
1. Chang, C.H; Bartz, M. L. C.; Brown, G.; Callaham, M. A.; Cameron, E. K.; Dávalos, A.; Dobson, A.; Görres, J. H.; Herrick, B. M.; Ikeda, H.; James, S. W.; Johnston, M. R.; McCay, T. S.; McHugh, D.; Minamiya, Y.; Nouri-Aiin, M.; Novo, M.; Ortiz-Pachar, J.; Pinder, R. A.; Ransom, T.; Richardson, J.B.; Snyder, B.A.; Szlavecz, K. (2021). “The second wave of earthworm invasions in North America: biology, environmental impacts, management and control of invasive jumping worms.” Biological Invasions, 23(11), 3291–3322. https://doi.org/10.1007/s10530-021-02598-1 https://www.srs.fs.usda.gov/pubs/ja/2021/ja_2021_callaham_002.pdf
2. Marie R. Johnston and Bradley M. Herrick, “Cocoon Heat Tolerance of Pheretimoid Earthworms Amynthas tokioensis and Amynthas agrestis,” The American Midland Naturalist 181(2), 299-309, (6 May 2019). https://doi.org/10.1674/0003-0031-181.2.299
Angela Gupta is a professor of forestry at the University of Minnesota Extension and specializes in terrestrial invasive species. She’s done invasive-species early-detection education and outreach for about 15 years, including on jumping worms. She holds a master’s degree in organizational management from Spring Arbor University in Spring Arbor, Michigan, and a bachelor’s degree in forestry from the University of Kentucky.
Gupta will be one of the panelists discussing the jumping worm’s presence in North America and its threat to the landscape during the Ecological Landscaping Alliance (ELA) 28th Conference & Eco-Marketplace, a virtual event to be held February 23 and 24, 2022. The discussion, “Understanding the Jumping Worm Problem,” will be moderated by Mark Richardson and will also include panelists Christopher Evans, with the University of Illinois Department of Natural Resources and Environmental Sciences, and Brad Herrick, with the University of Wisconsin-Madison Arboretum. The panel discussion will take place from 2-3 p.m. EST on February 24.
For more information or to register, visit www.ecolandscaping.org.
