Beetles, weevils lead battle against invasive plants
A couple of helpful bugs are having a significant impact in the battle against invasive plants in western Wisconsin.
For the past few years, the Wisconsin Department of Natural Resources office in Baldwin has been rearing special beetles to aid in their efforts to curb the spread of purple loosestrife, an invasive plant that chokes out native vegetation in wetlands.
According to Mike Soergel, wildlife manager at the Baldwin office, purple loosestrife was first arrived in the United States from Europe. People thought the purple flowers were pretty and brought the plants along with them to transplant here.
"The problem is the plant is very aggressive," Soergel said. "It has the ability to take over wetlands. That dramatically reduces plant diversity, which can in turn harm wildlife."
To save local wetlands from the ongoing march of purple loosestrife, chemical treatments and physical harvesting have been used. But the most effective treatment seems to be the use of loosestrife beetles.
The local DNR officials have been using the beetles for about eight years with great success, Soergel said.
The DNR office orders beetles from the state DNR office in Madison in the spring. The mating beetles are placed on netted loosestrife plants inside the Baldwin facility and the wait begins.
By the middle of July, the beetle larvae and new beetles emerge and begin to devour the captive plants. When the transformation from larvae to beetle is in full swing, DNR workers have just a matter of hours to place the beetles on loosestrife plants elsewhere in the region.
"It's critical to get them out right away," Soergel said. "There's not a lot of food left for the beetles once they emerge. If we don't place them fast, there will be starvation losses."
The DNR crews take the beetles to numerous locations throughout western Wisconsin and place them on patches where purple loosestrife is starting to take over wetlands.
One site is a Town of Cylon wildlife area. Another is the St. Croix River Islands on the border of Wisconsin and Minnesota. Another loosestrife site is along the Mississippi River in Pierce County. One of the newer treatment sites is below the Kinnickinnic River dam in River Falls. All of the beetle sites are on public lands, but Soergel said private landowners can also work with the DNR to combat loosestrife.
Once the beetles have been deposited in a location, they remain there to battle loosestrife for years to come. If their food source runs out, the flying beetles will move about to find additional loosestrife stands to attack.
Soergel said the beetles only destroy the loosestrife invader and they don't bother other plants or humans.
Apart from the loosestrife beetles, Soergel said the local DNR also uses a different beetle to fight leafy spurge, another invasive plant in the region. The DNR office also uses a type of moth and beetles to attack spotted knapweed, yet another invasive plant that is found in the area.
These bugs aren't reared locally but are ordered from the state and are simply transplanted to the infected areas when received.
"Wisconsin has been very aggressive when it comes to invasive species," Soergel said. "They haven't just thrown their hands up and said the species can't be controlled. And their efforts are working."
@t:Perch Lake, between Somerset and Hudson, may soon have its own successful biological control project to brag about.
Homestead County Park, along with its partners Beaver Creek Reserve near Eau Claire and Golden Sands Resource Conservation & Development Council in Steven Point, is helping rear milfoil weevils that will eventually be transplanted into Perch Lake in early August.
Right now, the weevils are being raised and fed in large 100-gallon tanks at Beaver Creek Reserve. The weevils love to eat the invasive aquatic plant called Eurasian milfoil.
For the past decade, Perch Lake has been infested with Eurasian milfoil and the infestation has been getting worse each year, according to Homestead Park manager Justin Townsend.
"Within four years of its detection, milfoil had taken hold of the entire rim of Perch Lake," Townsend said.
Townsend said county employees have used chemicals to combat milfoil in the past. They have also had divers pull the weeds at their roots to eradicate the vegetation, but the plants just keep coming back.
For the past few years, more and more lake organizations across Wisconsin have been giving milfoil weevils a try, Townsend said. Homestead Park and Beaver Creek Reserve combined to secure a DNR grant to give the biological control effort a try over the next two years.
At present, Perch Lake is using volunteers to harvest Eurasian milfoil plants that are sent to Beaver Creek as food for the growing weevils. When the rearing stage is done, according to Vanessa Meyer, summer weevil intern at Beaver Creek, the small bugs will be brought to Perch Lake.
The hope is that the weevils will help reduce the milfoil infestation, which creates large mats of weeds and causes problems for swimmer and boaters alike.
"We probably won't be able to see definitive results in the first year or so," Meyer said. "But we hope there will be positive results for years to come."
Townsend said he has one concern about the potential effectiveness of the weevil project. Panfish apparently like to eat the small creatures and Perch Lake has a large population of those fish.
So only time will tell if the weevil effort is the right fit for the local lake, Townsend said.
"You'll never get rid of the milfoil, but you should be able to get control of it," he said. "It's extremely effective and relatively cost efficient. It's costing county taxpayers very little money."
If it works, Townsend said lake users will be thrilled.
"This just seems like a more permanent solution for dealing with milfoil," he said. "And it's completely safe. The weevils don't bother swimmers and they don't harm other vegetation in the lake."