Invasive Aquatic Weed Creeps Across Great Lakes Region
The Associated Press
4 February 2017
MINNEAPOLIS — An aquatic weed is creeping across the Great Lakes
region that grows really fast and is very hard to kill.
Scientists don't know a lot yet about starry stonewort, but
they're hurrying to find out more. The plant, which forms dense
surface mats in lakes, first turned up in North America in 1978 in
the St. Lawrence River in New York state. Researchers think it
probably arrived in ballast water from ships entering the Great
It wasn't a big concern for about 30 years, but then it took off.
Now it's widespread on Michigan's Lower Peninsula, where it has
infested more than 200 inland lakes, and parts of western New
York. It was found in Wisconsin in 2014 and in Minnesota in 2015.
It has reached some lakes in Indiana, Pennsylvania, Vermont and
What is it?
The name comes from a tiny, white, six-pointed-star-shaped
“bulbil” on the stems. The plant is considered beneficial and even
endangered in its native Europe and Asia. But for some reason it
turned aggressive in American waters.
It's difficult to kill with herbicides because it doesn't have a
vascular system that could carry the poison to the entire plant,
said University of Minnesota invasive species specialist Dan
Why it's a concern
The weed mats can be a nuisance to boaters and anglers.
Scientists are also concerned about the potential harm to native
plants, fish habitats and other disruptions to aquatic ecosystems.
But Larkin said there's almost no peer-reviewed research
documenting the adverse effects. For example, it isn't known yet
whether it crowds out wild rice. Still, experts wouldn't be
sounding the alarm if they weren't worried.
Researchers are just starting to understand the conditions in
which the plant thrives, and modeling suggests that large swaths
of the U.S. could be highly suitable, including the mid-Atlantic
states, the Great Plains and much of the West, Larkin said.
How it spreads
It reproduces when plant fragments and bulbils break off, and
they can hitchhike on contaminated boats and trailers. Recent
discoveries have often been concentrated near public accesses such
as boat ramps. Scientists don't know yet how long those plant
fragments can stay viable out of water, Larkin said.
It was confirmed in September in Lake Winnibigoshish in Minnesota,
but that infestation probably went unnoticed for years. That
finding is concerning because the Mississippi River flows through
“Big Winnie,” a popular fishing destination and wild rice lake. No
infestations have been found downstream, though monitoring
continues, said Tim Plude, an invasive species specialist with the
Minnesota Department of Natural Resources. He said the species
doesn't seem to like fast-moving water.
How to control it
It's tough. Wisconsin has had some success with an expensive
method known as DASH — Diver Assisted Suction Harvesting. Divers
hand-pull plants and feed them into a suction hose.
Researchers hope to learn this summer whether a different approach
worked on Lake Koronis, a popular recreational lake in central
Minnesota where the weed was first discovered in the state. Crews
used a mechanical harvester, aided by a diver, and followed up
The best strategy is prevention. Boaters are urged to thoroughly
clean their watercraft, trailers and other equipment of plants,
mud and other debris before moving them from one body of water to