Purple Loosetrife Program FAQs
Purple Loosestrife is a non-native invasive plant that can spread rapidly throughout wetlands and shorelines. Left unmanaged, it forms dense stands that crowd out native vegetation, reduce wildlife habitat, diminish biodiversity, and negatively impact the health of our lakes. Treating infestations while they are still relatively small is the most effective and cost-efficient way to prevent larger, more expensive problems in the future.
Purple Loosestrife does not recognize property boundaries. Seeds can spread by water, wind, wildlife, boats, and people. Managing isolated patches on individual properties is far less effective than treating infestations across the entire lake system. By coordinating treatment, the TCFLA can help protect all six lakes within the Tiger Cat Flowage while reducing future treatment needs.
Thanks to years of volunteer monitoring and treatment efforts, Purple Loosestrife has remained relatively small and well managed. We do not have large, dense populations. However, new plants continue to appear each year, making early detection and prompt treatment essential to preventing this invasive species from becoming established. As a result, most of our treatment is for small stands and single plants.
Recent Wisconsin Department of Natural Resources (WDNR) permitting requirements require treatment activities to be conducted under an approved permit and in accordance with state regulations. To ensure compliance and achieve the best results, the TCFLA has hired a licensed aquatic invasive species management contractor experienced in identifying and treating Purple Loosestrife.
Using a qualified contractor helps ensure:
• Treatments meet WDNR permit requirements.
• The correct plants are treated.
• The appropriate treatment method is selected for each location.
• Herbicides are applied safely, accurately, and only where needed.
• The environmental impact is minimized.
The contractor will primarily use Renovate 3® (active ingredient: triclopyr), a selective aquatic herbicide approved for use in wetlands and along shorelines.
Renovate 3 targets broadleaf plants such as Purple Loosestrife while having much less effect on grasses, sedges, rushes, cattails, and many other desirable native wetland plants. This selectivity helps preserve healthy native vegetation that benefits fish, waterfowl, pollinators, and other wildlife.
The herbicide will only be applied where Purple Loosestrife is present and according to the product label and WDNR permit requirements.
The treatment method depends on the size, location, and density of each infestation. The contractor may use one or more of the following methods:
• Cut-and-treat (cut stem application): Mature flowering stems are cut and herbicide is applied directly to the remaining stem to minimize herbicide use while preventing regrowth.
• Selective foliar spray: Small infestations or patches may be sprayed directly on the leaves using low-volume equipment designed to minimize overspray.
• Hand removal: Very small or isolated plants may be hand-pulled when appropriate, taking care to remove as much of the root system as possible.
• Monitoring and follow-up: Treated areas will be monitored by volunteers to evaluate treatment success.
The contractor will choose the method that provides the greatest effectiveness while minimizing impacts to surrounding native vegetation.
The treatment window is currently scheduled for August 14–17. Weather conditions may impact the timing of the work, and any updates or schedule changes will be posted on the TCFLA website as information becomes available.
Early to mid-August is generally considered one of the best times to treat Purple Loosestrife because:
• The plants are actively growing and flowering, allowing them to readily move herbicide into their extensive root systems.
• Plants are easier to locate when in bloom.
• Treating before seeds fully mature helps reduce the spread of new infestations.
• Herbicide treatments during this period generally provide the greatest long-term control with fewer retreatments.
Timing treatments correctly improves effectiveness while reducing the amount of herbicide needed over time.
Probably not. Purple Loosestrife produces large numbers of seeds that can remain viable in the soil for several years. Successful management typically requires monitoring and follow-up treatments over multiple years. By treating infestations early and consistently, we can greatly reduce their spread and protect the long-term health of the Tiger Cat Flowage.
No. The cost of this treatment program is being paid by the Tiger Cat Flowage Lake Association and its members. Property owners who grant permission will incur no cost for treatment.
Wisconsin law requires landowner authorization before treatment can occur on private shoreline property. Your approval allows the contractor to access your shoreline only for the purpose of identifying and treating Purple Loosestrife.
Please keep children and pets away from the immediate treatment area while the licensed applicator is working. Once the herbicide has dried on the treated Purple Loosestrife plants, shoreline activities in the treatment area may resume. Drying time varies with weather conditions but is typically within a few hours.
There are no restrictions on use of water in the treatment area for recreational purposes, including swimming and fishing.
There is no restriction on use of water from the treatment area to irrigate established lawn grasses. However, since it is a broadleaf herbicide, avoid irrigation on broadleaf plants such as flowers, shrubs, trees and native wildflowers.
Purple Loosestrife beetles (Galerucella spp.) are one component of a long-term, integrated management approach. These specialized beetles help reduce Purple Loosestrife growth by feeding on the plant, allowing native shoreline vegetation to better compete and recover over time.
Biological control is not an immediate solution, but rather a sustainable management tool that can provide ongoing support as part of a broader strategy.
As part of our long-term planning efforts, our preliminary strategy identifies three potential beetle release sites on the flowage. These locations will continue to be evaluated based on habitat suitability, shoreline conditions, and overall management goals. Additional details and updates will be shared as our planning process progresses.
Yes. TCFLA is exploring opportunities to partner with local resources on potential beetle-rearing and educational initiatives that could support our Purple Loosestrife management efforts. Community partnerships and education are an important part of our long-term strategy, helping residents understand invasive species management and how they can contribute to protecting the health of our flowage.
Yes. TCFLA is actively working with partners to develop a comprehensive, long-term Purple Loosestrife Management Strategy for the flowage. Planning discussions are scheduled with the Wisconsin Department of Natural Resources (WDNR), Sawyer County Conservation, Northwest Regional Planning Commission (NWRPC), to evaluate treatment options, monitoring strategies, biological controls, education opportunities, and future management priorities.
TCFLA’s updated APMP will provide a roadmap for continued aquatic plant monitoring, invasive species prevention, rapid response actions, and long-term management strategies. The APMP update allows us to incorporate lessons learned, current data, and evolving best practices to ensure our management efforts remain proactive, responsible, and aligned with WDNR guidance.
There are many opportunities to participate! TCFLA welcomes members interested in learning more, supporting education efforts, monitoring invasive species, or joining the Purple Loosestrife Committee. The committee is a passionate, collaborative, and fun group of volunteers working together to protect the health and future of our flowage. Check out our Get Involved information on ways to participate.