Chemical Updates

2018 Chemical Treatment Plan

After five years of successful treatment, for most of the lake, the sheer volume and acreage of the non-native and invasive Milfoil and Curlyleaf Pondweed have been       significantly reduced.  If you talk to folks around the lake, it seems pretty unanimous that the chemical program has dramatically improved the water quality and improved recreational usage of Cossayuna Lake.  After four years of treating Curlyleaf Pondweed, the seed beds have been significantly reduced.  So, we are not planning to treat for Curlyleaf this year.  We will attempt to control any remaining Curlyleaf areas through harvesting early in the season, before the seeds have an opportunity to mature and drop.

We are, however, again planning to apply herbicides to try to keep the Milfoil in check.  Keeping the milfoil under control proves to be a difficult task.  There are still some problem areas that fuel the spread to other areas, and areas of regrowth.  An assessment done in September identified areas where milfoil was growing.  The most problematic area was the South end of the Lake where milfoil has made a huge resurgence; there are thick beds of milfoil covering most of the South End.  Our ability to treat in the South End in the last couple of years has been very limited.  Last year only the very northern section (by the little island) was treated, and the result after a couple of years of very limited treatment has been this huge resurgence in most of the south end.  This is not just a problem for the South end, but for the whole lake.  Milfoil is spread through fragmentation.  When boats go through these areas the propellers cut the weeds and fragments float to wherever the water carries them.  Since prevailing winds through the summer are generally from the south, all of these fragments float in a northerly direction, throughout the lake.  Just anecdotally, every time I was in the water around my dock last summer, I would see milfoil fragments floating along, always floating from south to north.  I would always try to scoop up as many as I could see, but of course that?s just a fraction of the ones floating by all the time.  And these fragments end up at various locations throughout the lake, wherever the winds carry them, and then regrow in the new areas.  

Besides the South end there were other smaller areas of milfoil growth also identified.  Most of these areas, many cove areas where the fragments get trapped, are most likely regrowth from the fragments floating up the lake.

Last year we revised how we approached planning for the chemical treatments, attempting to take a whole lake approach, to better address the remaining problem areas.  So, while the lake has looked so much better over the last few years, sometimes out of sight, out of mind, and we don?t see the urgent need to be vigilant about the milfoil.  But it is important; if we don?t keep it in check, the milfoil that will be cut and disbursed by boat motors going through these weed beds will re-root all around the lake again.  Clear today, may not mean clear tomorrow?.

A funding source was established for Lake Management projects, that includes: herbicide treatment of targeted weed beds to prevent the spread of invasive species; harvesting designated weed beds as they emerge throughout the growing season; water testing to ensure safety.  We have been working with professional applicators and many educated individuals regarding the betterment of our lake. 

Please donate to support the Lake Management program for herbicide treatment.  Funds will be used to employ the most strategic method possible. If everyone contributed to this fund we would have adequate funds.  While donations in any amount will help, we suggest donations of $100, $200, $300 or whatever you can invest in this program will make this a whole lake effort and continue to keep our lake in good shape.  It?s important to do this now as we must coordinate our program well before the growing season begins.

Please make the choice, donate, and help keep Cossayuna clean of invasive weeds.


Please go to the Forms & Applications page on this website and download the 2018 Participation Form. 

Please record your donation there under LAKE MANAGEMENT PROJECT.

THANKS! Your donation will help Cossayuna Lake continue to recover its health.