Managing Eurasian watermilfoil often requires a long-term commitment and a combination of management techniques. Mechanical harvesting, hand removal, bottom barriers, biological controls, and aquatic herbicides are all commonly used to reduce infestations and improve waterway access. Each method offers advantages and limitations, and many lake managers rely on integrated management programs that combine multiple approaches to achieve their goals.

One herbicide that has gained significant attention in recent years is ProcellaCOR®, a selective aquatic herbicide designed to target invasive plants while minimizing impacts on many native species. Lake associations and resource managers across the country have used ProcellaCOR to combat persistent milfoil infestations, often reporting successful control of invasive growth and improved conditions for recreation and native plant recovery.

However, as with any management tool, questions remain about potential long-term effects and environmental persistence.

Findings from Lake George

Following a ProcellaCOR treatment in Lake George, New York, researchers conducted independent sampling of water, sediment, and aquatic plants to better understand how the herbicide behaved within the ecosystem after application.

According to the study, degradants associated with the herbicide were detected in the upper layer of sediment five months after treatment. Researchers also reported finding the herbicide’s active ingredient, florpyrauxifen benzyl, in deeper sediment layers more than a year after application.

These findings have generated discussion among lake residents, scientists, and resource managers regarding how herbicide compounds interact with lake sediments and whether long-term accumulation may occur under certain conditions.

Balancing Benefits and Concerns

For many lake communities, ProcellaCOR has become an important tool in the ongoing effort to control invasive milfoil. Dense infestations can significantly impact recreation, property values, water flow, and native aquatic plant communities. Effective control methods can provide substantial benefits when invasive species threaten the health and usability of a lake.

At the same time, some residents and environmental advocates have expressed concerns about possible unintended consequences of repeated herbicide use. Questions have been raised regarding sediment persistence, impacts on non-target organisms, and the long-term effects on lake ecology. While current research continues to evaluate these issues, many stakeholders are calling for additional monitoring and independent studies to better understand the full environmental picture.

The Importance of Integrated Aquatic Plant Management

The debate surrounding Eurasian watermilfoil management highlights the complexity of aquatic ecosystem stewardship. There is rarely a single solution that works for every lake or waterway. Factors such as infestation size, waterbody characteristics, management goals, budget, and environmental considerations all influence the selection of appropriate control methods.

Mechanical harvesting continues to play an important role in many aquatic plant management programs by physically removing plant biomass from the waterway without introducing chemicals into the ecosystem. Harvesting can improve navigation, reduce nuisance growth, and remove nutrients contained within the harvested vegetation. In many cases, harvesting is used alongside other management strategies as part of a comprehensive aquatic plant management plan.

As research continues and new information becomes available, lake managers, regulators, and stakeholders will need to evaluate all available tools carefully. Ongoing monitoring, transparent reporting, and science-based decision making remain essential for protecting both recreational access and long-term ecosystem health.

The conversation surrounding ProcellaCOR and Eurasian watermilfoil management is likely to continue as additional studies are completed. For lake associations and water resource managers, understanding both the benefits and potential tradeoffs of available management options remains a critical part of maintaining healthy and usable waterways.

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The Apple River Protection and Rehabilitation District (ARPRD) reported removing roughly 2.73 million pounds of aquatic vegetation from the Apple River Flowage as of June of this year. This follows back-to-back years where totals reached around 3.8 million pounds, highlighting a consistent and highly productive management program.

Keeping the Flowage Open and Healthy

The 640-acre Apple River Flowage sits within a watershed that covers more than 111,000 acres. As with many Wisconsin waterways, invasive and fast-growing native plants—like coontail and curly-leaf pondweed—can quickly limit boating access, trap nutrients, and reduce dissolved oxygen levels if left unmanaged.

Through consistent mechanical harvesting, the ARPRD helps maintain navigation channels, improve water flow, and reduce the buildup of decaying plant matter that can lead to poor water quality. Unlike chemical treatments, mechanical removal takes the vegetation out of the water entirely, helping reduce nutrient recycling and long-term regrowth.

A Sustainable Approach to Aquatic Management

Mechanical harvesting is one of the most effective and environmentally responsible tools for managing dense aquatic growth. By physically removing weeds rather than killing them in place, this method helps protect fish habitat, limit algae growth, and keep waterways open for recreation.

The Apple River Flowage’s ongoing success shows how local commitment, steady maintenance, and the right equipment can make a lasting impact on the health of a waterway.

Learn about ARPRD

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The harvester and operators were on lease from the White River Flowage Lake Management District. The harvester, by the end of work on June 27, harvested an estimated 50,000 pounds of aquatic vegetation currently choking out the waterway.

A very positive impact on the millpond can be seen from the Highway 73 bridge. The channels cut are  extremely obvious and show what a clean body of water can look like. A healthy millpond remains the focus of most Friends members. If the millpond is not maintained, impacts on other parts of the White River will be noticed in years to come.

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“I know how important the water is to residents who live adjacent to it and all residents of Chestermere. Weed harvesting and weed control are an uppermost issue in most people’s minds,” interim CAO Pat Vincent said.

Chestermere Community Operations removed 132.5 harvester loads of weeds in 2023. Compared to 2022, when they removed 254.5 loads.

“We have been dealing with a flowering rush infestation, and it seems were enjoying some success in 2023 with the amount of flowering rush being removed from the lake is significantly lower than 2022, which to me is a good sign that we have been dealing with this issue effectively,” Vincent said.

The vegetation is then composted and used throughout the community.

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Save Minnewawa Association was formed in 1977 and they purchased their first aquatic vegetation harvester in 1982. Since the harvester has been in use, not only have the amount of weeds decreased, but the water clarity has significantly increased.

A big reason for this is because there are fewer weeds dying in the lake and decomposing in the bottom of the lake. Also, the weeds contain a huge amount of phosphorous which is being removed along with the weeds. The more phosphorous in a lake, the more algae growth, therefore the lower the water clarity.

The board has heard the suggestion of controlling the weeds by using chemicals instead of the weed harvester. The cost of the chemicals is very prohibitive though. It was $250,000 dollars and the lake had to be treated twice a year for the first 5 years; a price tag of a half million dollars. Compared to approximately $25,000 a year it takes to run the weed harvester.

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Last year, high, turbid waters and a layer of sediment carried into the lake by flooding and rainfall reduced weed growth, explained Cushing. With clear water and low lake levels this summer, those familiar with the bay were expecting more weed growth than they’ve seen, but Cushing believes the sediment may also be helping to suppress weed growth this summer.

SAAWA removes 400 to 500 tons of weeds from the lake each summer with the help of an Aquarius Systems Aquatic Weed Harvester. The weeds contain a lot of water, Cushing explained and once they dry out, 40 to 50 tons of organic matter remains. Removal of the weeds prevents the weeds from dying and decaying in the water where they would release phosphorus and nitrogen, the very nutrients that feed algae blooms.

Currently the weed growth is outstripping our ability to pull them out of the lake, but we are convinced there are benefits to removing as much growth as possible, before it decomposes, spoiling water quality, increasing phosphorus as well as producing conditions for blue green algae growth.

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Harvester operators volunteer their time and currently have 2 primary and 2 backup operators that received training from Aquarius Systems. There are several volunteers lined up for next year already too. According to Richardson, each load of harvested vegetation is approximately 275 cubic feet and weighs about 4,480 lbs.

The aquatic vegetation had been so bad the past few years that some did not even attempt to get their boats and pontoons in the water. After the second day of cutting, fishermen and recreational boaters were taking advantage of the open water to enjoy some of their favorite past times. The cut vegetation will be of great use to many as well, Dragonfly Nursery will use the vegetation as compost and farmer Brad Fougner will use the material as fertilizer next year.

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Excerpt from Chautauqua Lake Association Newsletter

The CLA currently has the equipment, knowledge and manpower to continue the annual task of plant harvesting. Harvesting has a low impact on aquatic habitat, compared to other options is inexpensive and greatly improves our lake conditions for the community.

Harvesting is a need that Chautauqua Lake in New York will have even if other options are taken. We have participated in both dredging and spraying in the past. Experience, scientific recommendations and the information from other lake communities advises us of the constant need for harvesting.

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The mild winter and warm spring have contributed to the explosive growth of two invasive weed species. To better control the weeds, the Village of Wauconda is developing a comprehensive multi-year lake management plan. The goal of the plan is to evaluate Bangs Lake and determine the best courses of action necessary to establish and maintain proper balance between aquatic plants, fishery, animals, and other elements so that Bangs Lake remains a healthy and viable body of water for year-round active and passive recreation.

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