written by Ben Eland, BEA's Garden/Facilities Director
It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures. - Charles Darwin
Earthworms are known as ecosystem engineers, because they have the capacity to alter the physical, chemical, and biological properties of our soil. Most of us tend to think of earthworms as beneficial, but unfortunately an invasive and potentially destructive species, the Asian jumping worm, is spreading quickly throughout our region. Asian jumping worms behave differently from native and naturalized worm species: they feed voraciously on organic matter, and they operate at a shallow soil depth, leaving nutrients near the surface and less available to plants’ roots. Furthermore, nutrients left in the droppings of Asian jumping worms are more likely to wash away in the rain, further depleting the soil. These worms spread very quickly once they are introduced, they have the potential to make large swaths of soil less hospitable to native plants, and they disrupt the delicate relationships between plants and soil microorganisms. Research shows that Asian jumping worms tend to displace or out-compete all other worm species, which amplifies their negative effects on the ecosystem.
Identification
Asian jumping worms live up their name, and will thrash and even jump off the ground when disturbed. They move differently than other worms, with a notable “S-like” movement (and hence are also known as snake worms). They do look similar to other earthworms, but their bodies are darker, with a cream colored band near the head (known as the clitellum). Other earthworms tend to have lighter colored bodies with a clitellum that is closer to the same color as their body, and the clitellum is farther from the head. Most earthworms have a slimy texture, but Asian jumping worms are smooth to the touch.
Prevention
Asian jumping worms are an annual species. They die after the first frost, but they leave cocoons full of eggs that lie dormant through the winter (these cocoons are very small – about the size of a mustard seed). The worms hatch in spring, and you are most likely to see adult worms in warm summer months. They reproduce asexually, which helps their population to grow quickly. Their eggs are often found in mulch and in the soil of potted plants. While we haven’t yet spotted any Asian Jumping Worms at Boxerwood, our mulch pile could be a potential source of spread. Boxerwood’s community mulch pile largely consists of leaf litter collected by the City of Lexington, which could easily contain this species’ eggs. No mulch source can be guaranteed to be free of these worms or their eggs.
Currently, the best way to prevent spread of these worms is to heat mulch above 104℉ before spreading it in your garden – this is hot enough to neutralize the eggs. You can do this either from creating a compost pile that gets to high temperatures (check with a soil thermometer), or by covering mulch or infested soil with clear plastic to amplify heat from the sun. This process is known as solarization, and usually takes several weeks. Other controls are being researched, but currently there is no surefire way to stop the spread of Asian jumping worms.