RPBCWD does not control invasive aquatic plants for recreational purposes. If you're considering control of aquatic plants along your shoreline, you likely need a permit for aquatic plant management from the Minnesota DNR.
The Riley Purgatory Bluff Creek Watershed District (RPBCWD) conducts aquatic plant surveys for multiple lakes on a rotational basis. The purpose of the surveys is to monitor native and non-native plant populations to inform decisions about aquatic plant management for lake health. The District does not intentionally manage aquatic plant populations for recreational benefit.
Curlyleaf Pondweed (Potamogeton crispus) and Eurasian Watermilfoil (Myriophyllum spicatum) are the most problemative invasive non-native aquatic plants in the District. The District uses herbicide treatments to control these Aquatic Invasive Species (AIS) to a level that allows native plant populations to increase.
RPBCWD applies for a permit from the Minnesota DNR to control aquatic invasive species in a lake. If a permit is granted, RPBCWD will work with a contractor to apply aquatic herbicide to control aquatic invasive plants in that lake. Treatments managed by RPBCWD occur at no cost to residents.
The decision to treat a particular lake is based upon aquatic plant surveys that determine the distribution and density of target invasive species. See schedule below for lakes considered for treatment this year.
|LAKE NAME||Target invasive species||Herbicide name||Location(s)||Size of treatment||Treatment timing*|
|Mitchell Lake||Curlyleaf Pondweed||Flumioxazin||See map||12.9 acres||May 17 (Wednesday)|
|Lake Susan||Curlyleaf Pondweed||Flumioxazin||See map||5.3 acres||May 17 (Wednesday)|
|Red Rock Lake||Curlyleaf Pondweed||Aquathol||See map||13 acres||May 17 (Wednesday)|
|Rice Marsh Lake||Curlyleaf Pondweed||N/A||N/A (no 2023 treatment)||N/A||No treatment in 2023|
|Lake Riley - 1||Curlyleaf Pondweed||Diquat||See map||9 acres||May 17 (Wednesday)|
|Lake Riley - 2||Eurasian Watermilfoil||N/A||Decided not to treat due to plant survey results||N/A||No treatment in 2023|
|Staring Lake||Eurasian Watermilfoil||N/A||N/A (no 2023 treatment)||N/A||No treatment in 2023|
|Lotus Lake||Eurasian Watermilfoil||Diquat||See map||22.92||June 15 (Thursday)|
*Dates may change due to weather. See "Timing" below.
This page will be updated as new information, including treatment dates, becomes available. Please bookmark this page and check back for updates.
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RPBCWD staff only know the general timeframe of a treatment until weather predictions become more precise and lake water temperatures reach treatment standards. Actual treatments dates are typically selected the week before treatment, however applicator availability, MnDNR permit approval, or abrupt weather changes may affect scheduling or not allow us to determine exact dates until shortly before treatment.
Treatments are scheduled during optimal weather conditions (low wind, water temperature near 60 degrees F). Dates of treatment may change due to changes in weather or other unforseen circumstances.
All Curlyleaf Pondweed treatments must occur before June 1st per MnDNR regulations. to protect native aquatic plants. The herbicides most commonly used to control CLP are detrimental to native aquatic plants, which typically begin growing after June 1st.
Eurasian Watermilfoil treatments typically occur mid-June to mid-July when the plant is most actively growing.
Selection of herbicides is based upon a number of factors including target invasive species, previous treatments, lake characteristics, cost, or other variables. After herbicide treatment, the Minnesota DNR recommends not using the lake water for these activities for the listed number of days.
(active ingredient: endothall)
|Drinking (people and pets)||3 days||3 days||None||None|
|Irrigation||7 days||5 days||5 days||5 days|
For the most recent information about treatment status, please check this webpage.
For other AIS or water resources management questions, contact:
952-607-6512 Ext. 4