By Abby Obenchain, Sault Ste. Marie Horticultural Society

One of my work colleagues here in Sault Ste. Marie recently discovered what he believes are Asian earthworms (Amynthas) in a plant he was repotting. These invasive worms pose a hazard to gardens and forests as they can cause “nothing grows here syndrome.”

According to University of Minnesota ecologist and earthworm expert Cindy Hale, a nursery in Pennsylvania with 30,000 hosta varieties lost half its plant stock to Asian worms that came in on a load of mulch. These worms have been found closer to Ontario, in both Minnesota and Wisconsin. Harsh winters appear to be a barrier to these worms, but as the climate warms they could establish farther north.

Also known as Asian jumping worms, Alabama jumpers, snake worms, or crazy worms, these worms are touted as being excellent for composting and as fishing bait. However, they can also mow through garden soil and leaf litter on the forest floor. In some areas of the Smoky Mountains, the jumping worm population is so high almost no leaf litter is left, which has dire implications for the forest ecosystem, including loss of many plant and animal species. These worms have a high metabolism and can live in very high densities. Red wiggler worms sold for composting are often contaminated with Asian earthworms.

So how can you help prevent the spread of Asian earthworms?

1. Throw away unused fishing bait in a sealed container.
2. If you compost with worms, keep them inside. Don’t add them to an outdoor compost pile. If possible, freeze worm castings for at least a week in an airtight bag before adding to garden soil.
3. Avoid moving soil around. Remember: even soil that has no visible earthworms can have earthworm eggs in it.
4. Avoid using community mulch. Mulch sold in bags is generally safe.

How to identify Asian earthworms

Asian earthworms are actually fairly easy to identify if you know what you are looking for. Three key features (also see graphic below):

1. Earthworms have a distinctive area on their body called the clitellum that is used in reproduction. In Asian earthworms, the clitellum is annular (encircles the body). In European earthworms, the clitellum is saddle shaped (does not go all the way around). The Asian earthworm clitellum is also less swollen than that of the European earthworm.
2. Earthworms have stiff hairs called setae growing along each of their annuli (ring-like segments that make up their bodies). Asian earthworms have many setae, and they grow close together. European earthworms have only 8 setae around each ring (they can be widely paired, closely paired, or separate).
3. Asian earthworms can jump! European ones cannot.

Thanks to Great Lakes Worm Watch for help with this article. Graphic adapted from Earthworms of the Great Lakes (Hale 2007), with permission.

Did you know…? Ontario has no native earthworms! The glaciers wiped out them out about 10,000 years ago.