Managing lake weeds

By Mike Scott

Weeds are an important element in the overall eco system of any lake. They provide food for some members of the lake environment and they also provide shelter from predators. But on the flip side, many lake problems start with a weed that grows quietly below the surface. For Oakland County inland lake property owners, understanding what’s growing in the water and how to treat or manage it can be the difference between a healthy lake and one slowly headed toward long-term damage.

Not all weeds or aquatic plants in Oakland County lakes are alike. It can be difficult to tell the difference between native and invasive weeds to the naked eye. The cost of doing nothing to address lake weeds can be not only financially high but ecologically disastrous.

Clients contact water resources practice leader Paul Hausler and his team of consultants at Progressive Companies to help with a strategy to protect a lake’s ecosystem. That first contact often happens when it is clear that an inland lake has become infested by one or more aquatic plants or weeds. Like some human ailments, the effect is often not noticeable until the problem is almost beyond repair.

“We often have (new clients) contact us when weeds are causing recreational or environmental issues or the (quality of) fishing is being impacted,” said Hausler. “By then, the problem is probably worse than they realize. Every situation is different.”

Most weed removal efforts are designed around invasive weeds. Invasive weeds are non-native aquatic plants or algae that were introduced into a lake ecosystem where they did not historically exist, often by boats. Because they evolved elsewhere, invasive weeds often lack natural predators or controls in Michigan waters, allowing them to spread aggressively and outcompete native species.

On the other hand, native weeds or plants evolved with Michigan’s fish, insects, and the overall lake ecosystem. They are important for many reasons, including as spawning areas for fish, providing a nursery habitat where young fish can hide from predators, and feeding grounds for insects and small organisms. Native weeds are an important component of the lake’s food chain. Some invasive weeds can overtake native plants and not only provide an eyesore but also damage the lake’s natural ecosystem.

Some invasive weeds can form dense mats that interfere with swimming, boating and other recreational uses.

The goal in lake weed management is to “create an environment where your native weeds and plants can grow back and thrive, Hausler said. “It’s best to work with a professional who understands what they’re doing and is unbiased.” He compared his work with inland lakes to that of a financial planner for future retirees.

The basic ways to treat weeds come down to four options: chemical treatments, harvesting, a hybrid of the two, and the occasional insect solution.

The types of allowable chemical treatments are regulated by the Michigan Department of Environment, Great Lakes and Energy (EGLE). The organization has more stringent chemical application guidelines compared to the U.S. Environmental Protection Agency (EPA), said Blake Cuthbert, vice president of lake management for Aqua-Weed Control, a lake and pond management firm, so those are the guidelines that residents should follow.

Detailed information about managing lake weeds and chemical usage is available through EGLE’s Aquatic Nuisance Control department, which issues permits statewide. Its website at Michigan.gov/anc provides updated information on herbicides that are or are not approved by EGLE, details about standard permits, and how and when chemical treatment can be applied to non-native species.

When questions come up about aquatic nuisance control and water quality permitting in Michigan, much of the responsibility runs through EGLE’s Water Resources Division. Amanda Bosak, who supervises the water quality and aquatic nuisance control permits unit, believes that lakefront property owners and those involved in making environmental decisions for a lake should be informed about the permit process and guidelines provided by the organization.

Bosak explained that her unit oversees permits related to chemical treatments and other methods used to control invasive or nuisance aquatic plants and organisms. These permits are required to ensure that any treatment conducted in lakes, ponds or streams complies with state and federal water quality standards.

“The goal is to balance effective aquatic nuisance control with protection of water resources,” Bosak wrote in an email. “Every permit application is reviewed to make sure proposed treatments will not cause unacceptable impacts to water quality, aquatic life, or public health.” Permits are required for chemical use, but not for non-herbicide harvesting.

The U.S. has a different set of regulations governing chemical applications used to remove freshwater weeds compared to other parts of the world. In particular, the European Union’s (EU) chemical and water protection laws are written to consider the impact of the “precautionary principle.” That principle is incorporated into the EU’s Water Framework Directive, which requires members to prevent pollution and achieve “good ecological status” for all water bodies rather than focusing only on chemical discharge limits.

Some members of the European Union, including Austria, France, the Netherlands, Belgium, Luxembourg,and Germany, have implemented partial bans or strict limits on some herbicides. The list of banned herbicides includes glyphosate or other active ingredients, especially in non-agricultural or public spaces and near freshwater.

In the U.S., any application of a pesticide or herbicide that results in measurable chemicals entering water must be permitted and comply with discharge limits under the Clean Water Act. The National Pollutant Discharge Elimination System (NPDES) permitting program regulates discharges from pesticide applications in a way that is consistent with the Clean Water Act, as outlined on the EPA’s website at epa.gov/npdes/pesticide-permitting. State environmental protection regulatory agencies, like EGLE, are often the NPDES permitting authority, issuing permits for activities in their state.

The EPA generally does not apply the precautionary principle as part of its requirements.

States that are considered to have more stringent laws governing herbicide applications in freshwater lakes include Maine, Massachusetts, Minnesota, Oregon, and Vermont, among others. Chemical use in freshwater lakes is governed primarily by state agency regulations, which take precedence when they are more stringent than EPA guidelines.

Applying aquatic herbicides to freshwater in Maine is generally illegal unless a specific wastewater discharge permit is obtained from the Maine Department of Environmental Protection (MDEP). A flyer from the MDEP states that chemical weed control in state waters “may not be applied” except in rare, permitted circumstances.

Massachusetts regulations restrict how close herbicides can be applied to surface water and sensitive areas, with limitations near drinking water supplies or surface water used for public drinking water. Defined buffer zones prohibit applications in these areas as well.

Minnesota designates certain chemical pesticides as “surface water pesticides of concern.” This designation triggers the need for best management practices and additional monitoring and protection measures when high traces of chemicals are found in the state’s waterways.

Oregon’s Department of Agriculture oversees a Pesticide Management Plan that focuses on protecting water quality in rivers and lakes from unnecessary chemicals.

Vermont residents and contractors may not apply pesticides, chemicals other than pesticides, biological controls, or other control methods in waters of the state without first obtaining an aquatic nmuisance control permit from the secretary of the Vermont Agency of Natural Resources. Among other requirements, residents must demonstrate that there is no reasonable non-chemical alternative.

In Michigan, each lake has different restrictions and requirements based on current information in EGLE’s database, which is updated as additional research or lake data is available.

Chemical treatment contractors require approval from 100 percent of lakefront property owners, a lakefront association if by-laws permit broad approval, or the approval of a special assessment district for an inland lake. A special assessment district can be formed if 51 percent or more of lakefront property owners approve and additional requirements are met.

Chemical treatments are particularly effective for preventing the spread of invasive species through fragmentation, according to Blake Cuthbert of Aqua Weed Control. This can happen when such invasive weeds as Eurasian milfoil, curly leaf pond weed, or starry stonewort are removed through harvesting or non-chemical weed removal. Fragments of the invasive weeds can be displaced to other parts of the lake, where they may hatch and expand rapidly.

“Some (invasive) plants can be killed systematically with the use of (herbicides) in a way that they don’t return the next year at the same level,” Cuthbert said.

Chemical herbicides do not always provide a complete solution, but it is often effective when EGLE guidelines are followed, said Jo Latimore, an aquatic ecologist and outreach specialist at Michigan State University. Chemical treatments can be difficult to apply, especially for non-professionals. An incorrect “dosage” can do more harm than good for the local ecosystem.

“Chemical treatments allow us flexibility with early detection,” Latimore said. “They can be used to target specific weeds.”

Chemical treatments can be difficult to effectively apply, especially for non-professionals, Latimore said. An incorrect “dosage” can do more harm than good, which is why anyone applying chemical treatment to Michigan lakes should follow directions provided by EGLE.

Weed harvesting involves direct human removal without chemical treatments. Mechanical equipment is most often used to cut and physically remove aquatic vegetation from above or below the water’s surface.

There are different types of mechanical aquatic weed harvesters used for this work. Most are boat-like machines with cutting blades and a conveyor system that lifts the removed material onto the boat and then off the lake for disposal. Hausler said some companies will give or sell the compost to farmers because of its value in supporting healthy soil for certain crops. Harvesting is usually first done in open water areas, such as parts of the lake near swimming docks or boat channels.

Manual hand-pulling is another harvesting method that is often used closer to shore, though it is labor-intensive. Suction harvesting is completed by divers and can also be expensive and logistically difficult.

“Harvesting doesn’t work as well with lakes that have a lot of sediment,” Hausler said.

Ty Nuottila is the owner and president of Oakland Harvesting in White Lake Township, an aquatic weed harvesting firm. He is an admitted proponent of harvesting invasive weeds rather than using chemicals when possible, referring to himself as a chemical minimalist. Nuottila believes that the majority of Oakland County lakes use some chemicals for weed removal.

“We have a short summer in Michigan, so I understand that people want (weeds) removed,” Nuottila said. “But when you kill stuff in your lake with chemicals, it’s like putting poison in there.” Nuottila adds that over time, regular chemicals can fill up the water column with harmful nutrients. One of the outcomes is the addition of “muck” at the bottom of a lake.

“That’s just (the accumulation of) years and years of layers of dead weeds,” Nuottila said.

Harvesting has been around for decades, and Nuottila said he generally doesn’t cut deeper than six feet below the water. The benefits of mechanical and targeted harvesting are that it creates more oxygen, which helps to filter out nutrients. That can also help create better water, which supports the local ecosystem.

“If you’re just putting in chemicals every year, it may result in needing to dredge the lake over time, which is extremely expensive and time-consuming,” Nuottila said. Yet that may be the only type of treatment that some lakefront property owners know. There’s a natural resistance to change that we often have to overcome,” Nuottila said. He believes many states have more stringent laws governing chemical use in lakes.

Minnesota limits the percentage of zones that can be treated unless there are variances granted under a lake vegetation management plan, which adds an extra layer of state oversight. Herbicides must be federally and state-registered and permitted by the state’s DNR for use in Wisconsin. Yet Michigan is regarded as one of the more restrictive states based on the permit and reporting requirements outlined by EGLE.

Both Hausler and Nuottila said that herbicide treatment and/or harvesting are most often scheduled one or more times from June through September. Lake associations that contract harvesters often choose to have at least one session completed by the July 4th week, which is considered the busiest water sports period of the year for most Oakland County lakes.

“That reduces the number of weeds during the max usage period,” Nuottila said. No one wants weeds to get all the way to the surface. They want as much wide-open, usable water as they can get.”

Nuottila often conducts a second harvesting period in August or early September, so that growth is scaled back to support oxygen spread for fish. He believes that most Oakland County lake budgets can accommodate two harvests per year.

“This (schedule) can open up a lake and help embrace the circle of life,” Nuottila said.

Diver-assisted suctioning is a newer form of harvesting where experienced divers will pilot dive boats to areas of the lake where they can pull weeds manually underwater, Latimore said. Some lake associations have decided to tackle diver-assisted suction harvesting on their own, provided they have members who are experienced divers.

Diver-assisted suction harvesting contracted to a third party is often the most expensive type of harvesting because of how manual and specialized the process is, Latimore said. While difficult and labor-intensive, this can be a way to avoid a common challenge with other forms of harvesting weeds – fragmented spread. When harvesting with mechanical equipment, a potential drawback is that small fragments of invasive weeds are not fully removed from the water. Those fragmented parts can actually spread and start to grow in other parts of the water, which is especially an issue with the invasive Eurasian milfoil.

“The fragments can float away and hatch elsewhere, which defeats the purpose (of harvesting),” Latimore said. “Divers have the ability to be more careful.”

Hausler believes harvesting is more effective at removing biomass from the lake. When managed properly, the amount of biomass caused by invasive weeds that might require removal is reduced over time, although regular attention and harvesting is still recommended.

The biggest disadvantage to harvesting is that it is not very selective, Hausler said. “You might be cutting down more of the native plants than you would want to. You’ll get the invasives, but it’s hard to pinpoint (native weeds) that should remain in place.”

EGLE guidelines require firms like Aqua-Weed to place signage on each piece of owned property about human restrictions following a chemical application. Cuthbert said this often includes guidelines for lakefront property owners related to swimming, irrigation, or agricultural and livestock restrictions for a minimum of 24 hours.

“They typically don’t want people swimming in a lake following a treatment for at least 24 hours,” Cuthbert said. “The dates vary.”

Bosak from EGLE noted that the department’s review process for chemical treatments considers several factors, including the type of product proposed, application rates, timing, and the specific characteristics of the waterbody. “We consider the size, depth, flow, and existing ecological conditions of the site,” she said in an email response. “Permit conditions are tailored to minimize risks while still allowing necessary control efforts.”

Bosak emphasized that permitting is not simply a box-checking exercise. The department may require modifications to treatment plans, monitoring, or public notification before approving a project. In some cases, applications are denied if they do not meet environmental standards.

For waterfront property owners and lake associations, the regulatory framework can feel complex. Bosak acknowledged that navigating it can be challenging, but she said the structure is there for a reason.

“Our responsibility is to protect the state’s water resources for all users,” she wrote by email. “That includes today’s residents as well as future generations.”

Bosak’s perspective underscores the careful, often technical work that goes into decisions most people only notice when weeds crowd a shoreline or treatment notices appear at the boat launch. Behind those postings is a permitting system designed to weigh competing interests and keep Michigan’s waters healthy over the long term, throughout the state. She acknowledged that EGLE is a resource available to all residents.

One of the most prevalent and troubling invasive weeds is the starry stonewort, which is not actually a plant weed. It is a large, bright-green freshwater macroalgae that grows underwater. It has become prevalent in many freshwater lakes in the Midwest. Starry stonewort forms dense, thick mats on lake and pond bottoms that can grow to several feet high and six to eight feet thick.

“Starry stonewort is chemically resistant, and spreads like a virus,” Nuottila said. “They creep into voids in the lake and stay there. They’re like a cancer.”

Nuottila said he used to live on Round Lake in White Lake Township. Over the course of several years, starry stonewort had taken over the lake, making it hard to maintain fish and engage in many recreational activities.

“It’s our role to help make your lake more resilient, so it is less impacted by invasive weeds,” he said.

Eurasian milfoil is an invasive aquatic plant first introduced to North America in the mid-1900s. Its aggressive spread makes the weed one of the most problematic invasive weeds in Michigan’s inland lakes.

This milfoil species is a submerged plant, meaning it grows entirely underwater but often forms dense mats at the surface, as opposed to the lake bottom. The weed has long, flexible stems and feathery leaves arranged in whorls around the stem, giving it a soft, plume-like appearance.

Like many invasive weeds, it spreads quickly and can take over large parts of a lake or water body when not treated. Hausler from Progressive Companies estimates that invasive milfoil can take over 80 to 90 percent of a lake’s weeds when left untreated.

“The challenge is that it just grows so much faster, and takes over the native (weeds),” Hausler said. “Plus, when it grows back, it grows faster than native plants.” He recommends harvesting as an option once the milfoil is more under control, but every situation is different. “You need to carefully manage your plan, whatever it is.”

Nuottila said that his company will regularly be contracted to harvest invasive milfoil, foxtails, water lilies, and lily pads, the latter of which can be extremely difficult to manage. One of the biggest challenges with any invasive weed is that they have no natural or native counterbalance to keep them in check, which explains their ability to spread in a fragmented manner.

“It’s like when we had the issue with zebra mussels in Michigan lakes over the years,” Nuottila said. “There’s nothing here to help keep them under control.”

Both starry stonework and milfoils are hearty and spread like “wildfire,” Nuottila said. “They just squeeze everything else out.”

Hausler said a chemical-only approach is often best suited for deeper lakes where harvesting along the lake bottoms is difficult at best, and often impossible. Depending on the lake’s profile, spot treatment may be effective. Some herbicides can help control particularly challenging invasive weeds. He adds that some weeds can build a level of resistance to herbicides over time.

A hybrid approach entails both weed harvesting and chemical treatments, and is the most common approach used by “60 to 70 percent” of the Oakland County lakes that his firm consults for, Hausler said.

Aqua-Weed also provides chemical treatment for the removal of other types of algae, which reduces water quality. Cuthbert recommends that most lakes get tested for algae regularly to determine in advance if there is an issue.

Most algae problems in Michigan are driven by excess phosphorus and nitrogen, which commonly come from lawn fertilizers, older septic systems, agricultural runoff, or excess stormwater. Algal blooms can cause illness in humans, kill or seriously harm pets and livestock, and force the reduction of lake activities. Excess algae also robs lakes of oxygen, which harms native species and the lake’s ecosystem.

“Testing is really critical for algae because you may not always see those issues,” Cuthbert said. “It’s a big part of what we do.”

EGLE indicates that when applied properly under permits, chemical treatments that rid lakes of weeds are intended to minimize risk. Studies show herbicides like 2,4-D and fluoridone can negatively affect fish, according to the results of studies published in the National Library of Medicine and a 2022 study developed by the Department of Forest and Wildlife Ecology at the University of Wisconsin-Madison.

However, trace elements of many chemicals are found in fish species after regular treatment, Nuottila said. Federal and state governmental regulations may suggest that trace levels in some fish can still be safe for human consumption, but Nuottila believes Michiganders should make their own decisions about fish consumption based on personal comfort levels. He also says native fish can be adversely impacted in the short-term following an herbicide treatment.

“Fish will feel sick for a while after a treatment,” Nuottila said. “We’ll see instances of fish kills and dead snails following (multiple chemical) treatments. He referenced the fact that Upper Long Lake in Bloomfield Township, to his knowledge, has not been chemically treated for over 20 years, with lakefront association leaders instead choosing to harvest only. “You see the (positive) impact of how their fish population is,” Nuottila added.

Chemical treatments and harvesting may not be the only options for some invasive weeds, MSU ecologist Latimore said. Some native insects have been found to help eliminate the growth of invasive weeds. The larvae of the milfoil weevil, for example, feed on the invasive Eurasian water milfoil weed. They burrow into the weed and force it to collapse when faced with large volumes.

As a result, milfoil weevils have been raised in laboratory settings over the years and used to help reduce invasive milfoil spread in lakes throughout Michigan and other parts of the Midwest, Latimore said. However, the approach doesn’t always work because the ecosystem of one lake will vary from that of others.

“Bugs are picky as part of our habitat,” Latimore said. “We’ve seen some success in lakes where these weevils can survive, but every lake and (ecosystem) is different.

Another example of insect weed control is when certain species of beetles feed on purple loosestrife, an invasive weed that generally is seen above water on inland lakes. These weeds have spikey, purple flowers, and while less destructive than other invasive weeds, can grow quickly, forcing out native plants and adversely affecting water quality.

“These are options that some lake associations use, especially when they prefer to avoid using chemicals,” Latimore said.

Finding and removing invasive weeds early is important because there is the potential that they may not have spread and thus won’t need labor-intensive, expensive strategies for removal, Latimore said. Some lake enthusiasts will drop a buoy into the water when they identify a possible invasive weed for further investigation by an expert. Latimore said that is the approach that lakefront property owners have taken for Lake Ellen, located in the upper peninsula’s Mansfield Township.

“They’ve been able to keep a large portion of the lake free from milfoil layer for many years,” Latimore said. “That can happen when you’re vigilant.”

There are ways to help prevent invasive weed spread. Some launches around Michigan and throughout Oakland County have preventive boat wash stations that offer high-pressure air and/or a vacuum that can be used to clean off the boats.

The challenge, Hausler said, is a lack of oversight.

“Most (boaters) aren’t going to use (wash stations), especially if they don’t have property on that lake,” he said. A few lakes statewide may have these stations manned during busy summer boat days, which can be paid for through a fee to boat launchers. But that system is costly and impractical for most lakes to maintain.

Gull Lake in Kalamazoo is one example where a manned boat launch has helped to stem the tide of some invasive weeds, Hausler said. The Gull Lake Quality Organization operates a free, high-pressure hot water boat wash station at Prairieville Township Park to help prevent the spread of aquatic invasive species, according to the Fall 2024 GLQO Watershed Journal newsletter. Gull Lake is known for its healthy population of trout, salmon and other fish, Hausler added.

While property owners around Lake Ellen have been proactive, many lightly populated or remote lakes in northern regions of Michigan are in poor shape because invasive weeds have taken them over, Nuottila said. Fish populations generally fall if invasive weeds become prevalent in a lake.

“

This is what would happen in Oakland County for most lakes that aren’t (treated),” Nuottila said. “The invasives would just take over.”

He indicated that some lakefront property owners aren’t even aware that issues like a mucky bottom and fish kills are a result of overgrown invasive weeds. “People have been losing their lakes for decades,” he said. “It’s amazing what we can get used to with a lake full of weeds.”

Yet not every invasive weed is a sign that drastic treatments are needed, Latimore said. Some lakes have conditions where invasive species do not spread rapidly.

“People should remember that if an (invasive) weed is not naturally spreading and harming the ecosystem, you can live with them,” Latimore said.

Native weeds in general are an important component of a lake’s ecosystem. Native weeds and aquatic plants supply oxygen for native fish. Hausler and Latimore indicated that some inland lakes may need to consider removing native weeds as well if doing so creates a healthy balance for property owners and the ecosystem.

In a state like Michigan, where inland lakes and Great Lakes shoreline are central to both the economy and quality of life, that balance is not abstract. Treatments that are too aggressive can harm fish, invertebrates, and native plant communities. Too little management can allow invasive species to spread, choking waterways and limiting recreation, Latimore added.

Native species like lily pads and pond weeds may be removed using chemicals or harvesting as well, but are generally done for mainly recreational purposes, such as swimming, boating, and water skiing, Cuthbert said. Aqua Weed Control will chemically treat lily pads only in certain areas, such as around docks and to open channel paths for boats. The Holly firm only treats other native plants a maximum of 100 feet from shore at a maximum depth of five feet.

“We try to leave native plants where we can,” Cuthbert said. “You want to promote them because they are good for the habitat.”

Lakefront property owners may wish to remove invasive weeds and cut back overly abundant and dense native weeds so they can use the water more efficiently for warm-weather lake activities such as boating, skiing, fishing, and swimming. But weed control is critical to the lake’s long-term health, Latimore said. That also includes removing invasive weeds so that native weeds can thrive. Fish avoid areas where native weeds have been taken over by invasive weeds. That puts them at risk.

“If you lose native plants, that cascades and they lose habitat,” Latimore said. “Native plants provide spawning habitat for native fish.”

There are other legal issues to consider when disposing of invasive weeds around Oakland County’s inland lakes. One is to secure all approvals needed for chemical or harvested efforts. Michigan’s riparian laws give ownership of parcels of lakes, including the bottom lands, to lakefront property owners. State law requires that bottomland owners provide approval before certain weed removal actions are taken. Approval is also required from EGLE.

“Homeowners often own the portion of the lake in front of their property, perhaps in a pie-shape depending on the size and shape of the lake,” Hausler said. “Landowner permission is required.”

To help secure the approvals needed for such work, some lakefront owners and associations set up special assessment districts that require public hearings and approvals, Hausler said. EGLE can then acknowledge the legal authority to schedule an inland lake treatment once requirements are met. Hausler said that some lakes might also have deed restrictions that need to be addressed, such as Lake Sherwood in Commerce Township.

Mechanical harvesting generally does not require riparian approvals because it does not involve the use of chemicals.

Hausler admits that ongoing education is key and comprises much of his firm’s work. An inland lake specialist can offer recommendations backed by research that provide lake stakeholders with the best possible options for managing invasive and native weeds.

“The majority of fish use native weeds as part of their life cycle, so you want to have the right balance,” Hausler said. “You can use too many chemicals that offset the balance of the lake. Once you lose (that balance), it is hard to get it back. The average person won’t know that. Managing the weeds in your lake is more complicated than most people think,” he added.

Unfortunately, there are no quick fixes to lakefront weed control. It is a time-consuming, strategic, and often costly process. Latimore said developing a relationship with EGLE professionals like Bozak or members of her team at Michigan State or other state universities is beneficial because they can confirm information and requirements and aren’t biased toward any specific options.

“Then the benefit there is that with the state is that they aren’t selling you anything, so they’re looking out for (a lake’s) best interests. It’s a great resource,” Latimore said.

She recommends that lakefront property owners and lake enthusiasts learn how to identify invasive plants, and if they see something that looks questionable, take a sample, snap photos, and get them reviewed by inland lake experts. Researchers and water ecologists don’t mind reviewing weed samples even if they are native.

“Early detection makes all the difference,” Latimore said. In other words, if boaters or swimmers see something, they should say something. Without constant oversight and knowledge, managing the invasive weed population is difficult and potentially a costly and time-consuming endeavor.

“There’s not a (foolproof) long-term solution,” Nuottila said. “It sometimes feels like a war or battle you can’t fully win, but if you have a good plan, your lake will be better off. You have to remember that lakes will never be a swimming pool,” he added. “You want some weeds. The question is which to keep and how much to treat them.”