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Herbicide Weed Control

Read on to learn how the “fish window” impacts plans recommended by your LMDSC to use herbicide treatments for aquatic weed management in Long Lake, as well as many other WA waterways.



Certain common weeds are quite heavy around Long Lake again this year, more than a nuisance in some areas. Water lilies were successfully kept at bay with a permitted herbicide treatment, as planned by your LMDSC. But not the various types of pond-weeds. Why? Because of State herbicide restrictions limiting herbicides during the “fish window”. As Paul Harvey famously said, here’s “the rest of the story.”


Weed control treatments of Long Lake are done under permit coverage WAG994131 held by Thurston County Public Works. The permit coverage is issued by Ecology, and the treatment timing windows (aka fish window) are establish by WFWD to protect priority species of fish and wildlife. The “fish window” applies to the application of herbicides in specific water-bodies around the State, including Long Lake. The treatment window for the County use of approved herbicides in Long Lake is July 15th to December 31st.


A timely herbicide treatment was rejected by State agency policy again this year. On the recommendation of the LMDSC, the County submitted an exception request to the State "fish window" time-frame to treat specific weeded areas of the lake. Sadly, for the second year in a row, the request was denied. As a result, a treatment could not be applied when most effective as pond-weeds begin emerging, generally June to mid-July at Long Lake. By July 15th, weeds are generally thick in the lake, as we see again this year.


If treated late after July 15th, the dying weed mass releases excessive nutrients that feed algae growth, constrain water flow between lake basins, and inhibit recreational use. And regrettably, harvesting the weeds has proven not effective in shallow water due to physical operating constraints of the harvesting equipment. Click on the map below for WFWD information on what lakes have restriction windows, why, and which priority species are found there.



The LMDSC Weed Committee is working with the County to develop a plan for next year that includes, but is not limited to, an effective, responsible herbicide treatment for pond-weed control as allowed under State policy. Further, the treatment timing window limitations on uses of aquatic herbicides has been in place for 20 years and relies on the 2017 Supplemental Environmental Impact Statement (SEIS) created for Ecology. It has also caused confusion and frustration for many people around the state, and Ecology and WDFW are actively working on how to revise the system. Finally, many lake residents consider the State's current "fish window" restrictions for Long Lake as onerous, defy common sense, and should be revisited. Hopefully, revisions to the system will include detailed toxicology data in the review process that support responsible, effective treatments without harmful environmental impact.



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