At dusk Chaffin provided a tour of a colony of night crawlers — the most damaging of the worms — residing beneath a massive basswood tree behind his campsite. Each year, the worms can eat a season’s worth of basswood leaves, depriving the forest floor of “duff,’’ the carpetlike layer of decaying matter that is a critical component of northern American forests.Recently, a non-native earthworm was discovered at the University of Wisconsin
In a healthy forest, the duff keeps tree roots cool, germinates tree seeds and mushrooms, and provides a home for ovenbirds, salamanders and other small creatures. But below this basswood the earth is bare, a circle of hard-packed dirt 30 feet in diameter. Trees that might fare better here as the climate warms — hardwoods such as red maple and basswood — can’t take root in the packed dirt. Instead, the worms create ideal conditions for invasives such as buckthorn and garlic mustard, plants that evolved with them in Europe.
The Amynthas agrestis, also called the Asian crazy worm, was discovered last fall in the Arboretum, and the species survived the harsh winter. Officials said it’s the first time the species has been seen in Wisconsin, although it’s been in the East and Southeast U.S. for 50 years, Herrick said.The worms are presumed to have arrived in nursery plants received from the east coast.
The eight-inchers come with a ravenous appetite and an advanced ability to reproduce, reaching maturity in just two months and creating offspring without mating. When infestations happen, the worms devour nutrient-rich soil at the forest floor. Erosion sets in, making it harder for native plants to survive. In their place, pesky invasive plants can grow.
The best resource I know of online for earthworm-related problems is the Great Lakes Worm Watch, maintained by the University of Minnesota.