PLM plans to check Clark Lake for thermocline tomorrow (Saturday) and Monday.  Getting good results for the treatment depends on a pronounced thermocline—the difference in temperature of the top layer of water (10 to 20 feet) to deeper water.  If conditions are favorable, the treatment could take place on Tuesday.  So far, the colder weather has prevented the best conditions.

More on the thermocline. The temperature difference between the warmer surface water, and the colder deeper water, limits the exchange of material between the two layers. Steve Hanson notes “by waiting for the thermocline to develop before treatment, we can keep the majority of the product in the upper layer of water” where it will attack the hybrid Eurasian water milfoil (HEWM).  That difference in temperature creates the most favorable conditions for effective treatment.  The thermocline for both ends of the lake was last tested Friday, May 10.

A notice has gone out to property owners listing the treatment products.  It will be followed by a posting on lake shore properties prior to the treatment. Two products listed are Fluridone and Triclopyr.  Fluridone is expected to take out the HEWM, and the Triclopyr is on the notice in case some HEWM persists at the end of the summer. The manufacturer of the products, SePRO, will cover the cost of the Triclopyr to treat any spots if required.  Copper is also on the notice of no-restriction products, and will be used if any Starry Stonewort is found. Some lakes have been over run by Starry Stonewort.  If it shows up, the best solution is to treat it quickly.  

Steve Hanson puts the restrictions into context as they could be misleading.   “There are actually no irrigation restrictions (except for grass seedlings) at concentrations of 10 ppb (parts per billion) or less. We are targeting 6 ppb.  The grass seedling restriction goes away at 5 ppb.  People will see the 30-day restriction and be concerned understandably.”  He adds, “at the target concentrations there are no irrigation restrictions for established lawns or ornamentals.” Regarding the effect on fish, Steve Hanson notes “There are no restrictions regarding fishing or fish consumption associated with the use of Fluridone.  Fluridone, or any herbicide permitted in Michigan, does not bio-accumulate in the fatty tissue or muscles of fish or other aquatic organisms.”

When invasive weeds showed up in Clark Lake, the community took up the fight.  Lakefront property owners petitioned Columbia Township to established a special assessment district (SAD) so that the hybrid Eurasian water milfoil (HEWM) could be eliminated wherever found in the lake.  Other lakes found that leaving HEWM infestations unchecked clogged their waters-–reducing boating, destroying wildlife habitat and diminishing property values.

Previous treatments at Clark Lake were accomplished through the use of Tricolpyr.  Results were somewhat effective, but fell short of expectations in the judgment of Professional Lake Management (PLM), the company hired to treat the lake and measure results. Through their experience with other lakes, PLM believes Fluridone (brand name, Sonar) will be more effective and plan to use it this season.