If your shoreline area is within 150 feet of a curlyleaf pondweed or Eurasian water milfoil treatment area, and you'd like to opt out of treatment, contact Shauna Capron at scapron@rpbcwd.org or 612-791-9085.

Treatment Updates

UPDATES FOR CURLY-LEAF PONDWEED (CLP)

• April 27, 2026: CLP treatments are planned next week (week of May 4th) for Mitchell, Red Rock, Riley, Susan lakes.
• April 29, 2026: Any home within 150 feet of the treatment areas on Mitchell, Red Rock, Riley, and Susan may opt out of the treatment. Contact Shauna Capron (scapron@rpbcwd.org) to opt out.
• May 5, 2026: Treatments on Red Rock Lake and Lake Susan are scheduled for Thursday, May 7th.

UPDATES FOR EURASIAN WATERMILFOIL (EWM)

• Info pending delineation surveys of EWM

Aquatic Invasive Plant Control

The Riley Purgatory Bluff Creek Watershed District 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. RPBCWD controls invasive aquatic plants to benefit native aquatic plant populations, which are important for lake health, and not intentionally for recreation.

Curly-leaf Pondweed (Potamogeton crispus) and Eurasian Watermilfoil (Myriophyllum spicatum) are the most problematic 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. Treatments managed by RPBCWD occur at no cost to residents.

Treatment Decisions

RPBCWD staff make the decision to proceed with a treatment to control Curly-leaf Pondweed and/or Eurasian Watermilfoil based upon data from previous year's point intercept vegetation surveys, population trends of these invasive species in a lake, and delineation surveys for these species in the spring of a potential treatment year. RPBCWD must apply 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. 

The decision to treat a particular lake is based upon aquatic plant surveys that determine the distribution and density of target invasive species. RPBCWD also coordinates management efforts with city water resources staff.

If you're considering control of aquatic plants along your shoreline, you likely need a permit for aquatic plant management from the Minnesota DNR.

2026 Lake Treatment Information

Treatment dates are subject to change due to weather or other circumstances. Stay in the know: Subscibe to lake notifications by email.

Treatment Timing

RPBCWD staff only know the general timeframe of a treatment until weather predictions become more precise and lake water temperatures reach treatment standards. The general treatment timeline is selected about a week before treatment, however applicator availability, MN DNR 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. 

Curlyleaf Pondweed (CLP)

All Curlyleaf Pondweed treatments will be limited to early spring and will not extend beyond four weeks following ice-off OR until treatments can occur when water temperatures are between 50°F and 60°F, whichever is later (per MN DNR regulations). The herbicides most commonly used to control CLP are detrimental to other native aquatic plants. This regulation is designed to protect native plative which typically grow later than CLP and treatment effects are lessened because of it.

Eurasian Watermilfoil (EWM)

Eurasian Watermilfoil treatments typically occur mid-June to mid-July when the plant is most actively growing.

Herbicide Information

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 within or near treatment areas for these activities for the listed number of days.