THE HISTORY OF WEED CONTROL IN LAKE MITCHELL 1990-2014

by Dave Foley

Lake Mitchell has always been weedy. The water used to be darker and while this made it hard to see more than a couple feet into the depths, that cloudiness cut light penetration, which meant you wouldn’t find weeds growing in more than ten feet of water. In 1977 a sewer line was completed around Mitchell, ending the use of septic tanks, some of which used to leak nutrients into the lake which clouded the water. Water clarity improved allowing one to see bottom in 6 to 9 feet of water. The clearer water allowed vegetation to grow as deep as 15 feet.

The improved water clarity allowed a plant called naiad to thrive and in the mid-1980s, great mats of it plant grew to the surface of the lake and it drifted to shore creating piles on the beach that looked like mini haystacks. The Lake Mitchell Improvement Board, which had been created in 1989, set up a roadside pick up program to collect the weeds. While this was happening, Eurasian milfoil made its first appearance.
This lime green plant, which resembles a delicate bottle brush, was carried in the ballast of ships from Europe that came up the St. Lawrence Seaway. Fragments of the plant escaped into the Great Lakes and were picked up on boat propellers and were spread into inland lakes when these boats were launched. It is estimated that over 500 lakes in Michigan have Eurasian watermilfoil.

Within a few years the masses of naiad were replaced by thick beds of milfoil, which clogged the coves impeding motorized boat traffic in these waters. The Improvement Board hired, Progressive AE, a lake management consulting firm, in the early 1990s and under their direction, a chemical treatment and harvesting program was begun to control milfoil. Initially milfoil seemed to grow predominantly in the shallow waters but within a few years it had spread into the main lake and was growing down as deep as twelve feet.

Milfoil is spread by fragmentation making chemical treatment the only viable means of eliminating this plant. The cutting of plants that occurs with harvesting will only create more plants. The thick growth of plants in the Lake Mitchell coves requires a combination of treatment plans. First chemical application is done to kill the milfoil, then harvesting is done to cut and collect native nuisance vegetation and the dead milfoil plants. In recent years The chemicals seemed to work more effectively and harvesting was discontinued although harvesting is under consideration for this year.

In the last fifteen years the acreage of milfoil in Lake Mitchell ranged between 100 and 300 acres but was generally on the increase, The Improvement Board changed consultants, hiring Restorative Lake Sciences in 2011. Using advanced GPS equipment,1888 survey points provided a complete picture of the lake bottom. Initially progress was made and the number of milfoil acres dropped but then the plant developed a hybrid species that was resistant to the chemical used. As a result in 420 acres of hybrid milfoil were treated in June of 2013.

During the winter of 2013-4 the staff of Restorative Lake Sciences tested milfoil samples with various chemicals and dosages to come up with a more effective chemical treatment for 2014. Their efforts paid off as only 264 acres were treated in Lake Mitchell last June.

Working with our consultant, Jennifer Jermalowicz-Jones of Restorative Lake Sciences, the Improvement Board has access to the latest developments in dealing with invasive plants such as Eurasian Water Milfoil. Another winter of plant research has helped modify our chemical treatment plan for this summer so that the acreage of milfoil in the lakes should continue to decrease.

In late May both lakes will conduct their annual GPS survey for milfoil. The treatment will take place in in mid-June as a small fleet of white motorboats and air boats will move systematically cover the lakes’ surface applying chemical. The milfoil will die and fall to the bottom within two to six weeks after treatment.

In 1997 I became aware that the lakes were being chemically treated and I was concerned about the impact on the ecology of the lake. Would it still be safe for swimming? Would it negatively impact the fishing? Could drinking water be effected? As a resident and property owner who swam in the lake and fished it year round, I didn’t want any mistakes made. When an opening occurred on the Lake Mitchell Improvement Board, I was appointed to the Board. Initially I was optimistic that milfoil could be eradicated and the lake could return to the way it was in the 1980s. I’ve learned that’s never going to happen; milfoil will always be here. Our best hope is to minimize its effect.