Asian crazy worm

Amnythas agrestis, also called the Asian crazy worm, has been found for the first time in Wisconsin, at the UW Arboretum.

They’re here. They’re hungry. They’re eager to propagate.

A foreign worm with a huge appetite has burrowed into the soil of the UW Arboretum, making scientists nervous about how the worm could affect the state’s forests.

“They basically consume the forest floor,” said Brad Herrick, Arboretum ecologist and research program manager. “They often do it quite quickly.”

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 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 worm is called “crazy” because it flops and wriggles vigorously when handled. Arboretum employees found it by chance last October while leading a field trip to show visitors nightcrawlers — themselves invasive worms from Europe that have been here for centuries. Preparing to pour mustard water on the soil, the preferred method of drawing crawlers to the surface, they were met with a surprise.

“Lo and behold we found another worm that until that moment we didn’t believe was in the state,” Herrick said.

Bernie Williams, an invasive species specialist with the Department of Natural Resources, was on the trip and confirmed the mystery worm’s identity.

The worm is darker in color than the pale and pinker European earthworm, the common worm found all across the state. It also has a smooth and flat band of milky white, unlike the raised, ridged band found on European earthworms.

The find came near the Arboretum’s visitor center. In spring more of the species were found there and in a few adjacent areas. The total area of coverage is about an acre so far, Herrick said.

It is believed the crazy worm first came to the U.S. from its native Japan and Korea in the soil of plants imported for landscaping. Wisconsin’s representatives likely hitched a ride aboard some nursery plants headed here from the eastern U.S., Herrick said.

Arboretum staff don’t know to what extent the crazy worm is in the grounds beyond the areas where it’s already been spotted. Boots, tools and vehicles are being washed regularly to keep the worm from spreading, and Arboretum employees are avoiding areas where the worm has already been found.

Commercial nurseries in Wisconsin are being checked for the crazy worm, and potential control techniques are being looked at. To date it’s not known if there’s a crazy Asian worm repellent or how appealing the newcomers are to fish.

“Fighting invasive species, like buckthorn and gypsy moths and garlic mustard, is a big part of our work here,” Herrick said. “We’re hopeful we can find a way to protect the Arboretum from these worms, and educate others about their impact.”

Madison.com reporter Bill Novak contributed to this report.

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