Home » Weaver Lake » Lake Management » 2005 Whole Lake Treatment2005 Whole Lake TreatmentThe Plan
The Minnesota Department of Natural Resources is planning to include Weaver Lake in a scientific study to test if curlyleaf pondweed can be controlled by treating a whole lake with very low doses of herbicide. The ultimate goal of this study is to see if such a treatment can reduce curlyleaf growth so that native plants can reestablish. A healthier plant community in Weaver Lake would improve water clarity, reduce the amount of curlyleaf fragments washing ashore, and create better habitat for game fish. Please read on to learn more about this experimental treatment.
Questions and Answers
What is WLCA's goal in managing Curlyleaf pondweed?
The WLCA is looking for an economical, long-term solution for reducing and controlling growth of Curlyleaf Pondweed.
Why use an herbicide instead of harvesting?
Harvesting works well to remove dense growth within 4-5 feet of the water surface, but Curlyleaf can grow in water 12 feet deep. The remaining plants continue to grow and reproduce. A whole lake herbicide treatment can reach the Curlyleaf plants at all depths.
How much will the whole lake herbicide treatment cost?
While a whole-lake herbicide treatment will cost about as much as one year of harvesting, the herbicide treatment should provide better long term control… more bang for the buck!
Will the whole-lake herbicide treatment kill all of the Curlyleaf pondweed?
No, but it should eventually make it grow much less densely. This means that we should see clearer water and less Curlyleaf fragments washing ashore in the years ahead. But it is important to have realistic expectations from the outset - it may take several years to reduce the Curlyleaf turions enough to see major improvement.
What kind of herbicide will be used, and is it safe?
The herbicide is called fluridone (Sonarâ„¢). It is a chemical that bleaches out chlorophyll in plants. Because Curlyleaf is the only plant present at ice out, that is the time when the herbicide will be applied so it does not affect the native plants. Since chlorophyll is only present in plants, fluridone is considered to be safe for fish, humans, and other animals.
Will I still be able to treat my shore with chemicals?
The DNR has assured us that they will still allow people on Weaver Lake to receive permits for chemical control of plants near their shores as in previous years, but we hope that the fluridone treatment will reduce areas of dense Curlyleaf growth enough so that no additional treatment is needed. Please check the plant growth near your shore before you decide to treat.
How will this herbicide affect lawns using lake sprinklers?
The concentration of the herbicide that will be in the lake is actually lower than the dose that would hurt grass. The herbicide will also be applied just after ice-out (mid-April). By the time you need to water your grass in early summer, the small amount of herbicide left in the lake will not be enough to hurt your grass.
Read the "General Use Precautions: Irrigation" on the Sonar A.S. Specimen Label.
What if it doesn't work? Will we harvest?
While we expect Curlyleaf to be reduced this year, this is an experimental treatment, so results are not guaranteed. Since the herbicide treatment rivals the cost of harvesting, we will not be doing both. The good news is that any remaining Curlyleaf will die off by mid-June.
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