HOLLAND, Mich. — A three-person team trolled up and down the Lower Macatawa River on Thursday, searching the slow-moving waterway for ludwigia.
In Michigan, three types of the popular aquarium plant are considered invasive: Ludwigia grandifolia, Ludwigia peploides and Ludwigia hexapetala. Broadly, they're together referred to as water primrose.
"They're more robust, they're more aggressive," said Bill Keiper, an aquatic biologist for EGLE, comparing the invasive species to the native varieties. "We know that it’s bad and it's spreading fast. We don't want to wait around and worry and try to figure out what the impacts are because by then it'll probably be too late.”
In 2023, water primrose was placed on the state's invasive species watch list, having been detected years prior in the Lower Macatawa River, as well as on the shorelines of Lake St. Clair and Lake Erie.
"These are the next up and comers," said Keiper, comparing water primrose to eurasian milfoil, an aquatic invasive plant that annually costs Michigan $25 million.
The thick mats of vegetation created by out-of-control water primrose could similarly choke out native plants and animals and smother water recreation if left untreated, according to the biologist.
"If it's in your lake and you're part of a lake association, you pay for that," Keiper said. "If we can stop an invasive species from spreading to a bunch of different water bodies, that essentially saves our citizens a lot of money."
On Thursday, Keiper's team flew a drone over the Lower Macatawa River, surveying how the water primrose had multiplied in recent months, especially after some areas had been previously treated with herbicide.
From his point of view, the invasive species had spread "a lot," Keiper said, likely aided by an unseasonably warm September. Still, he believes it can be controlled over time.
EGLE plans to review the results from its survey and develop an herbicide-based treatment plan, deploying it over the course of multiple summers, targeting the water primrose that grows in narrow bands along the shoreline while sparing native plants.
"From a treatment standpoint, this is pretty accessible," Keiper said. "Please report it."
If you're spending time in one of Michigan's many bodies of water and see a long, leafy green plant with showy yellow flowers and a reddish stem, report the sighting here.
