The visible invisible: impacts of invasive jumping worms

Contributor: Annise Dobson

Many of us have grown up thinking that earthworms are a sign of healthy, fertile soil. However, many earthworms found throughout Maryland are not native. Earthworms can be beneficial in their native ecosystems and agricultural settings, but their ability to re-engineer soil can completely restructure ecosystems and the microbial, plant, arthropod and vertebrate communities that live within them.  Much of what we know about invasive earthworms comes from studies of invasive European earthworm species, whose effects on forests are particularly notable in temperate North America. More recently, ‘jumping worms,’ (the common name for several similar-looking species belonging to the family Megascolecidae, also known as crazy worms, snake worms, Alabama jumpers, Jersey wigglers, Georgia jumpers, pheretimoids), have invaded temperate and tropical ecosystems across the globe. Their distribution is patchy throughout North America, and while often associated with urban and suburban landscapes, they are appearing with greater frequency in natural areas and forests. Once introduced to a location, jumping worm populations grow rapidly, and can grow to high densities in 4-5 years. Due to their ecological, economic and recreational impact, and the difficulty in removing them once they have been established, jumping worms have been chosen as MISC’s Invader of the Month for November.

Figure 1. Jumping worms alter soil characteristics, increasing erosion (left) and creating large macro aggregates (right). (Annise Dobson)

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Figure 2. Jumping worm appearance in late summer. Cream colored clitellum goes all the way around the smooth, metallic, darkly pigmented body. (photo: iMapInvasives)

Jumping worm invasions are unique in that they consist of multiple co-invading species including Amynthas agrestis, Amynthas tokioensis, and Metaphire hilgendorfi in temperate North America. Jumping worms grow and mature quickly, and some species can reproduce asexually, thereby quickly reaching high densities from an initially small invading population. They grow and mature much more quickly than European or native earthworms. While both lumbricid and jumping worms remove the organic horizon, the texture of jumping worm invaded soils is more stressful for roots, fungi and soil fauna. This is because jumping worms transform surface soils into large macroaggregates, described as ‘gravely,’ with the appearance of ground beef or spent coffee grounds. These changes to soil lead to erosion, nutrient leaching, root desiccation, and plant death (Fig 1).

The cascading effects of jumping worms on other species are far reaching. In areas of heavy infestation, anything that relies on the forest floor for food and habitat, such as soil fauna, native plants, salamanders, birds and other animals decline. Furthermore, jumping worm tissues can accumulate toxic metals, suggesting they could be a major pathway for metal bioaccumulation in higher organisms. In addition to deteriorating natural systems, jumping worm impacts are being felt by gardeners, plant nurseries, golf courses and community parks. The deep layer of loose castings created by jumping worms is particularly problematic for perennial plants (both native and horticultural), as well as parks and lawns used for recreation.

Jumping worms can be identified all year round by the distinctively granular soil, described as looking like ground beef or coffee grounds. Their presence can be confirmed in late summer when populations grow rapidly, reaching peak size and abundance. Key features include:

  • Thrashing behavior and high densities
  • Smooth, metallic sheen, often darkly pigmented, and 1.5 to 8 inches long
  • Clitellum often cream colored and goes all the way around the body, unlike the lumbricid species which have a raised and pink colored clitellum (Fig. 2)

Because we currently lack any viable control strategies, efforts should be put on limiting  

human-mediated dispersal of adults and cocoons. Fortunately, the worms don’t move very quickly on their own! Best practices include:

  • Require clean equipment provisions in logging and landscaping contracts (and encourage your neighbors and local government to do the same
  • Treat compost and mulch to 55 oC for 3 days
  • Prevent dumping of yard waste
  • Plant bare-root
  • Don’t move soil in tools, equipment, shoes
  • Don’t dump bait or compost worms
  • Don’t use compost and mulch of unknown origin

For more information see