May 21, 2007
Lake Washington association is updated on exotic plants in lake
By Roz Kohls
Lake Washington Improvement Association’s lake management contractor is more concerned about the lake’s Curly Leaf Pond Weed infestation, than its Eurasian water milfoil. Both exotic species hurt lake recreation, but curly leaf also hurts water quality, he said.
The contractor, Patrick Selter of Professional Lake Management in Pequot Lakes, updated the lake association’s members May 5 about its aquatic plant management in Lake Washington. The update was part of the 210-member association’s annual meeting, with a capacity-crowd, at the Dassel Rod and Gun Club.
Selter has been monitoring five sites in the lake for phosphorus, water clarity and Chlorophyll A.
Overall, there are no alarm bells sounding for Lake Washington. The Eurasian Milfoil didn’t bloom last year, pointed out Bill Craig of Dassel, of the association’s exotic species committee.
Selter’s test results for phosphorus, however, show a spike in midsummer, at the same time when the curly leaf weed dies back. He is concerned there might be a cause-and-effect relationship between the two, he said.
Integrated plant management involves mechanical harvest, and chemical and biological control. There is no effective biological control yet for Eurasian water milfoil or curly leaf, such as an insect or worm that eats it. Mechanical harvest costs $600 per acre, Selter said.
That leaves chemical control of the Curly Leaf Pond Weed in Lake Washington. The chemical chosen for the invasive species is selective. It won’t destroy other beneficial species such as cattails and native pond weeds, he said.
The herbicide is slightly less toxic than caffeine for humans. It also is designed not to hurt the fish in the lake. The chemical stays in the fish’s gut for three days, but people don’t eat fish guts anyway, Selter said.
In addition, the herbicide is applied only where it is needed. Selter uses an airboat that is guided by a computerized global positioning system. Selter pointed out his route on a slide of a computerized map of the infestation in the lake projected on the wall. The system is so accurate it showed where Selter retrieved his hat after it blew off in the wind, he said.
When Selter’s father-in-law started the company, Professional Lake Management, he used a row boat and a coffee can. Now, lake management can be very precise, Selter said.
Also, Selter implements control when the plants become a nuisance, and not just because they exist in the lake. There is no evidence yet that Eurasian Water Milfoil or Curly Leaf Pond Weed hurts fisheries, he said.
The time to act on controlling the nuisance, for example, is when residents can’t get their boats in the lake.
“Your kids go in swimming, and come out looking like the Swamp Thing,” he said.
Controlling exotic plants also will protect property values for the approximately 360 residences on the lake, Selter added.