Where We Treated in 2015, and Why

Chemical control of Eurasian milfoil is strictly regulated by the State.  According to the conditions of our permit we are allowed to apply triclopyr only to those “portions of the lake where EWM is too abundant (moderate to dense) to be cost-effectively managed using non-chemical techniques and is highly susceptible to fragmentation and continued spread.”  The state determines those locations based on the required quantitative aquatic plant survey from the previous fall.  Here are the results of that survey.  Red dots indicate dense milfoil, yellow is moderate, green is sparse, and empty circles indicate no milfoil found at that location.

2014 fall survey map

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These surveys are designed to take statistically accurate samples.  They do not report every instance of observed milfoil.  Rather they collect plant samples from a predetermined grid of locations and observe all the species present.  This allows the State (and us) to measure long term changes on all plant populations in the lake, to preclude unanticipated effects of the herbicide use.

Here are the results of the pre-treatment survey done this May.  For this survey every instance of observed milfoil was recorded.  Again, red circles are dense patches, etc.  This map also shows the areas approved for herbicide application.  For the most part they coincide with many of the densest growths of milfoil.

spring survey

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The herbicide was applied in the indicated areas on Tuesday, June 16th.  Note that not every location where there is milfoil was treated.  To those (including the author) whose littoral zone contains milfoil but was not treated, we offer apologies and hope that you understand the constraints under which these treatments are done.  We understand that there are divers who are experienced with Eurasian milfoil removal who can be hired to clear it from your shoreline.

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