NEW! 2022 Curly-leaf Pondweed Management & Monitoring Report

Please click the below report for the latest details of the hard work being done to manage the invasive aquatic plant curly-leaf pondweed on Lake Minnesuing.  February 2023: 2022 Lake Minnesuing CLP Management & Monitoring Report 

2022 Campaign to Raise Funds for Curly-Leaf Pondweed Abatement

During 2021-2022, the Lake Minnesuing Association engaged in a fund-raising campaign to support a comprehensive curly-leaf pondweed (CLP) abatement project in Lake Minnesuing. This project, considered by lake biologists as the most effective program to manage CLP, included multiple lake surveys to precisely locate the plants; hand-harvesting by divers to physically remove CLP throughout the lake; and herbicide treatment of a 13-acre dense concentration of CLP.

This project cost about $33,000 for 2022. All expenses were for professional experts and service contractors, with no costs for the efforts of local volunteers. The greatest share of funding came from individual donations of generous lake property owners and other individuals. A significant donation was received from the Carlson Family Foundation, a charitable entity of the owners of Minnesuing Acres Executive Retreat Lodge. Additional financial support was provided by the Lake Minnesuing Sanitary District and the Wisconsin Department of Natural Resources. This project could not have occurred without each of these generous contributions.

As noted elsewhere, curly-leaf pondweed management is a multi-year project. Grant funding will be sought for 2023 and beyond, but individual and organization donations will still be required in future years.

June 2022 CLP Update (Click Here)

What We Know as of February 2022 and Future Planning

As noted below, in late summer 2021 the Lake Minnesuing Sanitary District (LMSD) applied for a grant from the Wisconsin Department of Natural Resources (WDNR) to implement WDNR‘s and Onterra lake biologists’ recommended best practices for controlling curly-leaf pondweed (CLP) in Lake Minnesuing. This involved a three-year approach beginning in spring 2022 comprising annual hand-harvesting smaller colonies of CLP; herbicide treatment of three dense, large colonies; progress monitoring via lake surveys; and annual reports. The three-year grant request totaled $95,940 ($31,980/year), and was not funded by the WDNR. At the WDNR’s suggestion, the LMSD applied for a much smaller, one-year grant totaling $6610. The WDNR awarded this grant, funding the maximum they allow–65% of the total grant requested–namely $4362.60. (All WDNR grants require grantees to pay some portion, and grants in this category require a 35% cost-share contribution from the LMSD.) This grant funds solely the planning and monitoring component of the larger project, meaning pre-and post-treatment lake surveys and an annual report.

The lack of WDNR grant funding for hand-harvesting and herbicide treatment for 2022 required the LMSD to raise significant funds to support this project. The Lake Minnesuing Association conducted fundraising that has been partially successful thanks to the generous donations of many lake property owners. Nonetheless, additional financial support is still needed.

The LMSD has committed to and contracted for the 2022 comprehensive management of CLP. This includes contracts with Onterra to perform the lake surveys and provide an annual report and overall guidance; and contracts with companies that provide hand-harvesting and herbicide treatment. Herbicide treatment requires applying for a WDNR permit, which was submitted in February 2022. This permit application and related documents are posted on this website under Lake Plan.

The LMSD will apply for grant funding again in fall 2022 for future years since curly-leaf pondweed requires repeated control efforts over years.  

2022 Permit Application

2022 DNR Form 3200-4A

Lake Minnesuing Map CLP Details

WI DNR Endothall Fact Sheet

Aquathol K Label

Chemical Warning Sign

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. 

• Lake Minnesuing map of Curly-leaf Pondweed. 
• Curly-leaf Pondweed Fact Sheet 
• Aquathol K (Endothall) 

We have put together some additional details and resources regarding Curly-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)

Costs

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.