Belgrade Stream is a major pathway for milfoil spread, both within the watershed and beyond. Managing the stream and Messalonskee Lake together, rather than as isolated sites, reflects Maine’s growing emphasis on regional, watershed-scale conservation. This coordinated approach increases the likelihood of long-term success and represents a sound investment of public resources.

ProcellaCOR® is a targeted aquatic herbicide that affects invasive plants like milfoil while minimizing impacts to most native plant species. Prior to being approved for in-lake use by the U.S. EPA in 2018, it has been used for decades to control weeds in rice paddies grown for human consumption. It works at very low concentrations and is rapidly absorbed by targeted plants. It has been used successfully in several Maine lakes, including in Great Meadow Stream (Great Pond), where milfoil was reduced by over 97%.

The application process may take anywhere from a few hours to several days, depending on the size of the treatment area. The herbicide is rapidly absorbed by targeted plants such as variable-leaf milfoil and breaks down quickly in the water. Treated milfoil typically begins to decay within three weeks, with complete dieback—including roots—occurring within approximately six weeks. Some native plants may be temporarily affected. The goal of these treatments is to reduce milfoil growth to a level that can be managed sustainably over time. While some regrowth may occur after about two years, it is typically at much lower levels. For example, prior to treatment in 2022, 7 Lakes Alliance removed up to 50,000 gallons of milfoil annually from Great Meadow Stream. Since treatment, the largest annual removal has been just 30 gallons.

Property owners near treatment areas should see fewer floating fragments and rooted milfoil. In some cases, nutrients released during die-off may cause a short-term increase in algae. If your property is within 1,000 feet of a treatment site, avoid using lake water for irrigation for 24 hours.

Yes. 7 Lakes Alliance will continue using hand-pulling and benthic barriers in key areas previously maintained by Friends of Messalonskee. Manual removal will also be used within treated areas to manage any regrowth following herbicide applications and help sustain long-term control. 

In Maine, only the Department of Environmental Protection (DEP) and Inland Fisheries & Wildlife (IFW) are authorized to permit and apply aquatic herbicides. These agencies:

• Determine treatment locations and timing
• Hire licensed contractors
• Conduct pre- and post-treatment monitoring

7 Lakes Alliance, Friends of Belgrade Stream, and Friends of Messalonskee support DEP by providing local data, outreach, funding assistance, and follow-up physical removal, but do not make permitting or application decisions.

Yes. There are no drinking water restrictions associated with ProcellaCOR when it is applied according to the product label. It is approved for use in waterbodies that serve as drinking water sources. That said, Maine DEP does not recommend drinking untreated lake water at any time, regardless of herbicide use, due to naturally occurring bacteria, parasites, and other pathogens. For residents who draw water directly from the lake and have concerns during treatment, DEP can provide drinking water as needed. 

Yes. According to the EPA-approved label:

• Swimming and fishing are allowed after treatment
• There are no restrictions on human or pet contact with treated water

Some temporary irrigation restrictions (e.g., watering lawns or crops) may apply. Any applicable restrictions will be clearly communicated prior to treatment.

Extensive toxicity testing conducted for EPA review found ProcellaCOR to be practically non-toxic to fish, birds, mammals, and aquatic invertebrates when used within permitted concentrations. Studies on fish (including trout, minnows, and carp) show no evidence of long-term bioaccumulation at labeled doses. In cases where organisms were exposed to concentrations far exceeding permitted levels, any accumulation was temporary and metabolized within days. Bird species studied include mallard ducks, quail, zebra finch, and songbirds, with no observed toxic effects at expected exposure levels.

ProcellaCOR is highly selective, primarily affecting broad-leaf dicot plants, which include most invasive aquatic species. Many common native plants in Maine lakes are monocots, which differ in physiology and are generally less affected. Some native plants may show short-term impacts, but are expected to recover through seed germination in subsequent seasons. Invasive milfoil does not produce viable seeds in Maine, giving native plants a competitive advantage after treatment. In Great Meadow Stream, Great Pond, affected native plants began rebounding within the same year after treatment. 

ProcellaCOR is rapidly absorbed by plant material and breaks down through natural processes such as sunlight exposure and microbial activity. Under typical conditions, it dissipates relatively quickly, though breakdown rates vary depending on water chemistry, light, and organic matter. This behavior limits movement outside treatment areas and reduces long-term exposure.

Hand-pulling, DASH, and benthic barriers remain essential tools and will continue after treatment. However, in dense, system-wide infestations like Belgrade Stream, manual methods alone cannot keep pace with growth. Herbicide treatment reduces biomass over large areas, allowing long-term maintenance with physical removal to become feasible again.

No expected risk under normal use. Treatments will avoid nesting periods, and staff will be present to minimize disturbance. 

ProcellaCOR (florpyrauxifen-benzyl) does not contain PFAS. 

Restoring Belgrade Stream will take time, coordination, and sustained commitment. Community understanding and support are essential. Residents are encouraged to:

• Help prevent the spread of invasive species

• Stay informed

• Attend public meetings

• Ask questions and share concerns

• Help prevent the spread of invasive species

• Signup for email alerts from this website and other organizations