NORTH WEBSTER — Now that aquatic plants have returned to Lake Webster, the Department of Natural Resources is relaxing limits on how much weed control will be permitted this summer at the 774-acre lake in Kosciusko County.
Caps on how many acres of vegetation can be chemically treated by local residents were put in place six years ago after a lake-wide project that wiped out many plants, muddied the water, and upset anglers.
Since then the plant community has rebounded to the point that some areas, if left untreated, may not be usable by boaters or anglers. On May 4 lake residents hired a licensed pesticide applicator to treat 155 acres of Eurasian water milfoil, a species capable of forming dense mats on the surface. Much of the cost of the treatment was paid for with funds from the DNR Lake and River Enhancement program.
Plans are to permit the treatment of an additional 50 acres for control of various plant species along individual lake frontages, to be paid for by local residents. Last year the DNR permitted 25 acres of offshore milfoil control and the nearshore treatment. By then plant coverage had reached what is considered the optimum for the lake.
“Plants now cover 70 percent of the area where sunlight reaches the bottom,” said Jed Pearson, DNR fisheries biologist. “We want to maintain that amount to balance the interests of all lake users and protect the ecology of the lake.” Although more areas are being treated this year, Pearson says only 2,4-D herbicide was approved to control milfoil. In the past a less-selective herbicide known as SONAR was used.
Past treatments going back to the 1980s and 1990s using 2,4-D were generally successful at keeping milfoil in check.
Native plants such as coontail and pondweeds are expected to fill the void left by the selective, early-season killing of milfoil. If native plants do not fill the void after the 2,4-D treatment, Pearson says future weed control at the lake will be scaled back to what was permitted last year.
“We are not going to get into a cycle of overkill and recovery regardless of what herbicides are used,” Pearson said.
To monitor results of the treatment, various surveys involving hydro-acoustic technology and grab samples will be conducted throughout the summer by the DNR and lake association. The surveys will map the remaining plant beds and quantify plant coverage and abundance.
“What happens this year at Webster will be a key factor in where we go with weed control in the future,” Pearson said.