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Most earthworms present in the northeast are considered exotic. They were introduced in the 18th & 19th centuries via early settlers or through trade of soil and horticultural materials transported from Europe and Asia. New ones are continuing to be introduced spreading through fishing bait, compost and gardening supplies and plant exchanges.

In annual systems earthworms seem to enhance soil fertility through rich castings, soil porosity facilitation, and enhanced nitrogen and carbon cycling. In perennial ecosystems such as forests they pose an ecosystem health threat. They consume the organic top (duff) layers of soil. The loss is linked to the reduction in biodiversity often observed in invaded forests. This layer includes most of the nutrient exchange networks involving mycelium and roots. It is also where many seeds germinate. The change in forest floor structure and plant diversity also diminishes the habitat for other species such as ground nesting birds, mammals, invertebrates, and woodland salamanders.

For three years we have gathered data from 35 sites in five states (VT, NH, MA, NY, CT), in five USDA cold hardiness zones (4a, 4b, 5a, 5b, 6a). We recorded canopy and understory species diversity, maple seedling and sapling numbers, exotic plant presence, and earthworm species and abundance. Our findings indicate that worm presence is in direct relationship to forest damage levels. 

A new and highly destructive group of earthworm species is invading Vermont forests. These hail from Japan. Currently there are three Asian species that appear to threaten northeastern hardwood forests: Amynthas agrestis, Amynthas tokioensis and Metaphire hilgendorfi. They are known as snake worms or jumper worms. These worms appear to threaten regeneration of canopy and understory species. They produce very distinctive castings which have the appearance of loose coffee grounds.

Further research will be conducted to determine solutions which can protect forests from these worms, in particular the most damaging species of snake worms (Amynthas) and night crawlers (Lumbricus terrestris). 

In the interim, forest management plans can include strategies to minimize vector exposure: eliminate fishing bait refuse, minimize movement of horticultural materials andinspect all nursery species before planting for the presence of worms or signs, such as their characteristic castings. To determine whether you have these earthworms in your forest look for casting piles known as middens (Amynthas) and for holes and tunnels (Lumbricus). As a first warning sign for presence of both species, look for diminished duff and understory plant cover. There are several links below that can help you identify worms and their signs.

If you suspect you have invasive worms, please view the information below for how to sample and identify them.

Additional Information