IMPORTANT – Meeting was held on Thursday, Sept 30 at 6:30pm, Bennett Town Hall. Tyler Mesalk, Water Resource Management Specialist with the DNR was there to answer all of our questions. 

Click (here) to view the recorded presentation. 

We have put together some additional details and resources regarding Cu!AvnB16nG-kFJgQcPDCkYeL9bv3n4?e=GQtWRZrly-Leaf Pondweed and the Herbicide Endothall. The document also includes specifics on the Grant we are applying for.  (Click Here to read the document

Latest Information Regarding Curly Leaf Pondweed (CLP)

Several audience questions arose during the 9/1/21 meeting that presenter Lloyd Sinclair was unable to answer. Since that meeting, he consulted with two curly-leaf pondweed experts: Tyler Mesalk, Wisconsin Department of Natural Resources, and Tim Hoyman, Lead Aquatic Ecologist and owner of Onterra, LLC, the Lake Minnesuing Sanitary District’s contracted lake ecologists.

Q: Is the planned three-part approach consisting of herbicide treatment for the three large, dense CLP clusters; diver hand-harvesting for the small clusters; and annual lake surveys the best plan, regardless of cost? In other words, if money were no object, would different approaches be suggested?

A: The herbicide/hand-harvesting/survey plan is considered best practice by the DNR and Onterra lake ecologists, uninfluenced by cost considerations. Both entities say there is no better plan regardless of cost.

Q: Why not use herbicides instead of the proposed diver-assisted hand harvesting in the small clusters in many locations around the lake?

A: Herbicide treatment for small clusters is inadvisable because small amounts of herbicide dilute too quickly to kill the targeted plants, and often mistakenly kill native plants. To succeed at killing a small CLP cluster, so much herbicide would be needed that considerable collateral damage to desirable plants would occur, thereby leaving the general area more vulnerable to further CLP growth. Herbicide treatment is suitable for large areas where almost all of the plants are of one type—CLP—where the ratio of CLP to native plants is strongly dominated by CLP, thus minimizing the risk to native plants. This is the case for the proposed three dense clusters in Lake Minnesuing, comprising a total of 13.6 acres.

Q: Why not use diver-assisted suction harvesting (DASH) rather than hand-harvesting for the small clusters?

A: DASH is best suited for large areas and inefficient for small clusters spaced widely apart. The machine and apparatus are cumbersome to reposition from CLP site to site, resulting in excessive time moving the machinery relative to removing the CLP.

Q: It was noted, especially in high wind conditions, some fragments dispersed into the lake during hand-harvesting. Do these fragments cause new CLP colonies?

A: The principal method for CLP reproduction is via turions, small buds along the stems which fall back during the summer and embed in lake sediment for future growth. The goal of CLP management is to interfere with the plant’s life cycle by removing new CLP growth before germination, which is why treatment is done in May-June. Even if some plant fragments escape capture, they would be highly unlikely to create a new plant. The enormous reduction in the lake-wide CLP population from herbicide treatment and harvesting vastly outweighs the minor threat of plant fragment dispersion.

Q: Might we have a future meeting on CLP led by an expert in aquatic plants and invasive species?

A: Yes. DNR expert Tyler Mesalk has agreed to address our stakeholders at a future meeting, date to be determined and announced.

What We Know as of September 2021 and Future Planning

Timeline and Interventions to Date

Curly-leaf pondweed (CLP), an aquatic invasive species (lake weed), was first discovered in Lake Minnesuing in August 2018. An entire lake survey in June 2019 found the majority of CLP in the southern bay, with a few clumps outside the bay to the northeast.

Typical of invasive species, CLP has the potential to choke out native species by expanding to cover large areas of the lake surface with matted plants, thereby threatening the lake’s ecology, water quality, recreation, navigation, and aesthetics. While total eradication of CLP is not possible with current management techniques available, aggressive interventions can reduce it to the point of minor impact.

CLP is challenging to control because of its reproductive method. The goal of CLP management is to annually remove the plants before they reproduce via buds along their stems called turions, which look like small brown pinecones and have high reproductive rates. In the early spring, turions grow, then drop to the lake bottom and embed in the sediment. Individual turions produce new CLP growth in the spring, but at varying intervals between one and seven years. Eradication efforts do not kill the embedded turions. Therefore, a recently treated area can appear clear of CLP, only to show successive annual growth for up to seven years despite annual treatment. Such repeated treatment can eventually deplete the bank of turions in the sediment by annually eliminating new growth, thereby preventing additional turions for future plant growth.

In early 2020, the Lake Minnesuing Sanitary District (LMSD) was awarded a Wisconsin Department of Natural Resources (WDNR) grant of $20,000 (which required a donated match from the LMSD of $6667) to reduce CLP. The funds from this grant are now depleted.

Contracted lake ecologists from a lake management planning company called Onterra recommended one week of professional diver hand-harvesting in the first year, which was done during the CLP active growth period in June 2020. Divers hand-harvested 205 cubic feet of CLP. A subsequent lake survey indicated the CLP abundance was reduced.

Given this success, lake ecologists recommended another week of hand-harvesting for June 2021. However, additional CLP growth had been noted in September 2020, and again in early 2021. The June harvest focused on three areas of greatest CLP density, leaving many sites unharvested, and netted 511 cubic feet of CLP. A lake-wide survey done shortly after this harvest revealed the harvest had been inadequate due to the ten-fold increase in CLP since the previous year. The survey found CLP in 8% of the 272 locations lake-wide with depths suitable for lake plant growth, meaning CLP is now a significant component of Lake Minnesuing’s aquatic plant community. Although the CLP population is still most prominent in the southern bay, small clusters now exist in the entire lake.

Since hand-harvesting was inadequate to successfully reduce CLP, lake ecologists recommended a multi-year approach comprised of annual hand-harvesting smaller colonies of CLP; herbicide treatment of three dense, large colonies; and progress monitoring via lake surveys. This project is planned to begin in spring 2022 when CLP is actively growing, and be repeated annually for three years.

Alternative Control Strategies

CLP is typically managed via diver-assisted hand-harvesting; diver-assisted suction harvesting; and herbicide treatment. Each has advantages and disadvantages.

Hand-harvesting is best utilized when CLP colonies are small and not historically well-established. Advantages include strategic targeting of specific plants, ideally leaving native species largely undisturbed. Disadvantages included being very labor-intensive, expensive, and insufficient for large areas.

Diver-assisted suction harvesting utilizes a vacuum machine on a boat with a diver directing a suction hose on the lake bottom. Advantages include the potential of greater coverage area than hand-harvesting. Disadvantages include indiscriminately removing all aquatic plants, including native species; expense ($2500/day); and difficulty timing during the plant’s brief turion production and distribution period, making suction harvesting inapplicable to large areas.

Herbicide treatment is most effective when large, dense CLP colonies are present. Advantages include the ability to treat large areas (Lake Minnesuing’s dense CLP colonies total 13.6 acres; relative cost savings compared to more labor-intensive methods; and administration time allowing treatment during the plant’s brief turion production and distribution period. Disadvantages include killing of all aquatic plants–including native species–in the targeted areas and possibility of dispersion beyond the targeted area. (For areas under ½ acre, “curtains” can be utilized around the targeted area. This method is not feasible for Lake Minnesuing’s three large, dense colonies.) With recommended rates, the herbicide Endothall does not have apparent negative effects on fish species or invertebrates (snails, crayfish) that have been tested; has a half-life of 5-10 days with complete degradation in 30-60 days; is not likely to be a human carcinogen; and poses no unacceptable risk to water users if standard restrictions are followed. (WDNR)


As noted, the entirety of the WDNR $20,000 grant has been expended. Additionally, the LMSD has contributed $13,597 (more than covering the required grant match) to pay all incurred expenses.

WDNR offers grants for aquatic invasive species management. Such grants require a 25% match from the grant recipient. For example, if LMSD is granted $72,000, an additional $24,000 ($8,000/year) (25% of total expenditure) must be paid by LMSD.

Projected costs for the above-described three-year treatment and monitoring plan total $95,940 ($31,980/year). LMSD has applied for grant funding from the WDNR. If the grant request is fully funded, over three years the WDNR will pay a total of $71,955 and the LMSD will pay $23,985 ($7995/year). The required pre-application for grant funding has been submitted as required. The final application is due November 1, with results announced in about March 2022.

Lake Management Plan

Click below to read the full report

In 2017, the Lake Minnesuing Association Board selected Onterra, LLC to develop an objective lake management plan providing a variety of lake-related services ranging from science-based diagnostic/feasibility studies to comprehensive lake management plans consisting of aquatic plant inventories, stakeholder education, watershed and water quality analysis, and implementation plan development.

We applied and received a Wisconsin DNR Grant for approximately   $33,000 with a State share of 67%. 

The Plan Report was submitted in late 2019 and relative to comparable Wisconsin lakes, Lake Minnesuing is very healthy. That does not mean the lake is without its challenges; challenges that need to be met in order to maintain its health. 

Key Management Goals 

  • Manage our existing Aquatic Invasive Species (AIS); Curly Leaf Pondweed, Japanese Knotweed, Purple Loosestrife and Yellow Flag Iris
  • Prevent the introduction of new AIS
  • Protect and enhance shoreline habitat and reduce shoreline erosion
  • Protect current water quality conditions
  • Monitor water levels
  • Increase navigational safety
  • Increase LMA’s ability to communicate while growing partnerships with other lake related entities and organizations
  • Protect our existing outstanding native plant community
  • Conserve and enhance the fishery resource


Here is how we are addressing the Plan

  • Curly-leaf Pondweed: The Wisconsin Department of Natural Resources (WDNR) granted the Lake Minnesuing Sanitary District (LMSD) $20,000 for 2020–2022 to reduce the presence of a non-native aquatic invasive plant species called curly-leaf pondweed (CLP). CLP grows vigorously early in the spring shortly after the ice melts, potentially choking out native plants and rapidly spreading roots along the lake bottom. Plant removal is most effective during this period. Methods can include poisoning the plants, however this is not preferred since it also kills healthy plants and pollutes the lake with herbicides. The most effective long-term strategy for CLP removal is diver-assisted hand-harvesting, which involves divers swimming to the lake bottom and removing the plants by hand. This is a specialized, labor-intensive and expensive method, but the most effective at curtailing the growth and spread of the plants over time. Detailed lake surveys have precisely identified the location of CLP in Lake Minnesuing. The grant provides 75% of the funds, requiring the remaining 25% to be paid by the LMSD, some of which can be offset by Lake Minnesuing volunteer work. Divers removed 205 cubic feet of CLP over five days in June 2020. The LMSD has contracted for five more days of diver-assisted hand-harvesting, tentatively scheduled for the week of June 7, 2021. Project overseen by Lloyd Sinclair.  
  • Yellow Flag IrisYellow Flag Iris (YFI) is an invasive perennial with flowers that bloom from late May into early July and seed pods that spread and quickly overtake native plants. Overseen by Jim Giffin, the Wisconsin DNR completed a six-year grant on 12/31/2020 for Lake Minnesuing. This grant project was very successful at drastically reducing the presence of YFI on the lake. While the final report is pending, positive changes are evident and ongoing maintenance towards these efforts will be needed by individual homeownersPlease contact Jim Giffin or contact us for information on YFI.  
  • Healthy Lakes and Rivers:  The Wisconsin Department of Natural Resources has currently approved three Healthy Lakes and Rivers grants for shoreland property owners. Projects include rain gardens, driveway stormwater diversions, and rock infiltration pits. Additional projects can be added to this open grantIf interested please contact Jim Giffin or Contact Us.  
  • Clean Boats Clean Waters: Clean Boats Clean Waters is a watercraft inspection program to monitor and prevent the spread of aquatic invasive species. This Wisconsin DNR grant provides funds, combined with volunteer hours, to educate boaters on DNR regulations and watercraft inspections. Hired high school/college students are scheduled to work at the Hallberg boat landing most weekends from mid-May until Labor Day weekend with some Friday and holiday Mondays. If interested, contact co-managers Ann Mini or Laurie McGrath ocontact us for more information. 

Interested in volunteering to help us?