 Steve Hanson, Senior Regional Manager with PLM has 23 years of experience in the Aquatic Industry. He holds a Master of Science in Fisheries, a Bachelor’s in Fisheries & Wildlife. For over a decade Steve has been our representative for the Lake Fenton Invasive Species Weed Treatment program. Below is the presentation he gave at the August LFPOA Board Meeting. 1. Lake Fenton Aquatic Plant Management Program Goals
2. Activities conducted during 2024
3. Plant Trends
 4. Water Quality Data 2016-2023  5. Common Questions
Why do we need to continue with a management program if the exotic species are “under control”? First of all, once an exotic aquatic plant species is introduced to a waterbody, it is nearly impossible to eradicate it completely without taking extreme measures. These measures may include a quarantine for several years, limited use of the lake and nonselective treatment methods. In most cases, these are not practical or acceptable solutions. In the case of Lake Fenton, there are three known exotic invasive species we manage, Eurasian watermilfoil, Curly leaf pondweed and Starry stonewort. They differ dramatically in their structure, susceptibility and the way they react to herbicides. Eurasian watermilfoil was the species that prompted the Association to look for a lake-wide remedy to the aquatic plant problems that were being experienced in 2013-2014. Eurasian watermilfoil can overwinter and is one of the first species to grow in the spring. It can grow in excess of 10 feet in length and forms a surface canopy that shades out competitors, decreases water quality and impedes recreational uses of lakes it invades. Aquatic plants fall into two main groups, dicotyledons (dicots) and monocotyledons (monocots). Eurasian watermilfoil is a dicot. Curly Leaf pondweed and most of the native plant species in lakes are monocots. Eurasian water milfoil is capable of reproducing by multiple methods including seeds, rhizomes and fragmentation. Over the past decade a marked decrease in the susceptibility of Eurasian watermilfoil to conventional herbicides has been observed. Extensive genetic testing revealed that most populations are a hybrid of Eurasian watermilfoil and native milfoils. Native milfoils are much more resistant to herbicides. The hybrids typically exhibit less susceptibility to herbicides, tend to regrow at a faster rate. At one time, typical systemic herbicide treatments were expected to have multiple years of control, now season long control is questionable with most conventional herbicides. Systemic herbicide costs range from $350 - $1000/acre of treatment. Contact herbicides for controlling milfoil and Curly Leaf pondweed is $185/acre and the expected duration of control of the systemics does not warrant the use of systemics. In many situations, the May and early June treatments are in areas that contain both Curly Leaf and Milfoil. Instead of using a high cost herbicide to target milfoil and a lower cost herbicide to target the Curly Leaf, we can use a lower cost herbicide to target both with good effects. The milfoil species in Lake Fenton remains reasonably susceptible to Fluridone. Permitting restricts its use to not less than 3 years between treatment, and it’s cost is high due to the treatment requirements. Basically, we achieve a desired concentration of 6 ppb (parts per billion) in the top 20 feet of the water column throughout the whole lake and maintain it for 30-45 days. At the permitted concentration it is very effective against Eurasian watermilfoil and has very limited effects on any native plant species. As the milfoil returns in the years following treatment we spot treat to keep levels as low as possible until another Fluridone treatment is required. Curly Leaf pondweed is a monocot and does not respond to conventional systemic herbicides used for Eurasian water milfoil. It is controlled however, by Fluridone for the year of treatment. Curlyleaf pondweed reproduces primarily through turions that are deposited in the sediments. These turions are not affected by herbicides and typically millions of turions can occur within an acre of sediment that can persists for years. Curly Leaf reaches its maximum growth by mid-May to early June where it grows quickly to reaches the surface and create a canopy. Typically, once Curly Leaf is treated once in the early summer, it does not regrow to any extent during that growing season. Starry stonewort is not a vascular plant like Eurasian watermilfoil and Curly Leaf pondweed. It is a macroalgae. It forms a colony of individual cells making up a dense mass capable of growing several feet thick and covering over anything in its path. It is spread primarily through fragmentation. It is susceptible to copper products, although recent permitting changes have eliminated the use of copper sulfate in May and June. As alternatives, chelated copper products and flumioxazin can be used, although their costs are higher and their effectiveness is less. In dense mats, treatment effectiveness goes down because only the cells that are contacted by the herbicide will die. Untreated cells will quickly multiple. What would happen if we stopped treating the lake? Anyone who lives in an area on the lake that grows the early season Curly Leaf pondweed or Eurasian watermilfoil should already know the answer. If left unchecked, these species would severely impact their lake frontage and many shoreline areas would have mats of vegetation on the surface. Fragmentation would increase and the spread of milfoil would accelerate. Within a couple of years, the lake would be back to pre-program levels of nuisance vegetation reducing the recreational, aesthetic and economic value of the lake. Studies that evaluated the economic cost of invasive species on lakefront homes found a $30,000 decrease in home values where vegetation problems existed. Aren’t all of the problems the lake has a result of excess nutrients? In short, No. Lake Fenton does not have a nutrient problem. It has an exotic invasive species problem. The nutrient levels observed in Lake Fenton have been at or near the lowest recordable levels for the past decade. See the chart above that shows Phosphorus levels at 10 ppb, the lowest level the equipment can record. How do we know if there is going to be a treatment? PLM sends a tentative treatment schedule to all residents in the spring that lists the weeks that treatment may occur during the summer. The dates can vary depending upon environmental conditions. PLM notifies our contact at the lake the week prior to a treatment being scheduled with the treatment date and typically a map of areas to be treated. This information gets posted to the LakeFentonPOA.com website and Facebook page in advance of treatment. The lake was treated but we did not get a posting sign in our yard? PLM only posts the treated areas and a sufficient buffer from the treatment areas as required by law. Any swimming or irrigation restrictions only apply to within 100 feet of the treated area. Therefore, PLM does not post the whole lake when we do spot treatments in specific areas. What if my kids and/or pets were in the water following treatment? The vast majority of the herbicides used have no swimming or water contact restrictions on the EPA label. The State of Michigan requires we post a 24 hour swim restriction for any herbicide regardless of the EPA label. The risk to humans and pets exposed to treated water at treatment concentrations is minuscule at most. For example, a 150 lb person would have to drink 3,750 to 7,500 gallons of water treated at the maximum labeled rate of Diquat immediately after treatment to reach the lethal dose concentration 50% of the time. The lake was treated but we still have weeds at our frontage. Most likely, the plants you are seeing are native species that are not targeted by the treatment. It is not the intent of management to kill all of the weeds in shoreline areas. Leaving natives that are not resulting in a significant nuisance in shoreline areas reduces the risk of exotic species inhabiting that area, reduces sediment resuspension from wave action and provides valuable habitat for fish and other aquatic organisms. If you believe you do have exotic species in your area, contact me at [email protected] and we will inspect the area at our next visit. Do you treat weeds in the channels? Yes, in fact most weed treatment on Lake Fenton occurs in the shallow channels. Can you treat the lily pads around my dock and beach? Yes. In addition to invasive species, PLM also offers general weed treatment for individual properties. Riparian owners can schedule treatments for their shoreline by contacting Steve at [email protected]. About 30 residents on Lake Fenton did this in 2024. Comments are closed.
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