As reported earlier, Clark Lake was treated on Tuesday, May 21 for the invasive weed—hybrid Eurasian Milfoil (HEWM). Lakes that did not thwart this invader found that it curtailed recreational use of their lakes including boating and fishing, was detrimental to the ecology, and reduced property values. Clark Lake lakefront property owners supported the establishment of a special assessment district (SAD) to turn back the invader.
What’s new: PLM followed up two days after the treatment by taking concentration samples from around the lake and sending them to the lab in North Carolina. PLM’s Steve Hanson reports the “results were excellent.” The treatment product was calculated on a 20 foot depth thermocline to achieve a lake-wide concentration of 6 parts per billion. PLM achieved a concentration just short of that, and will take more samples on Tuesday, June 4th. They will schedule a bump-up treatment on Monday, June 10th. (A thermocline is where the top 10 to 20 feet of water is warmer than that below it which keeps the treatment product where the invasive weeds are).
The product being installed is Sonar. Steve Hanson explains it works slowly. “We need to have 30 to 45 days of contact time before the plants start to die off.” Treatment was late due to the cold weather and lack of a thermocline. “It will most likely be early to mid July before the HEWM starts to die.”
Regarding the bump-up, there will be a 24-hour swim restriction and the same irrigation restrictions as posted with the initial treatment. According to Steve Hanson, at “the current concentrations, there are no restrictions lawns and ornamentals. The only restriction that may still apply is for seedling/germinating grasses.” He adds “that restriction drops off at 5 parts per billion, which we may be under at this point.”
Below is the posting referred to.