August 11, 2021 at 5:20 p.m.
Eurasian Watermilfoil management on Lake Tomahawk explained
TLA to harvest over 100 acres of the aquatic invasive
Eurasian Watermilfoil management on Lake Tomahawk explained
The purpose of the update is to provide information regarding the harvesting treatments being used for the summer of 2021 on the lake, he added.
"Before I dive in, I want to remind everyone that we all have the same mission - to minimize and manage EWM on our beloved lake," he said. He expressed his frustration with the rapid spread of the invasive species and its density in many areas. He said he understands the plight of property owners who may be having a difficult time recreating on areas of the lake or even getting in and out of a bay or shore station.
EWM, he said, was first found in Lake Tomahawk in 2003. It was historically managed with the chemical herbicide 2,4-D and Hydraulic Conveyor System (HCS) boats, the precursor to the current Diver Assisted Suction Harvest (DASH) team boat.
Using the HCS boat is effective in managing EWM, Lottig said, but it is slow and expensive to operate. Since 2016 the use of 2,4-D has not been approved by the Wisconsin Department of Natural Resources (DNR) due to findings of adverse impacts on non-targeted native species. There is also evidence that 2,4-D promotes the growth of hybrid milfoil, which is chemically resistant. When applied in concentrations needed to combat the invasive, these chemicals will also build up in lake sediment where they have shown to have a clear detrimental impact on larval fish.
Lottig also spoke about two chemicals, ProcellaCor and Aqua Strike, which were part of a three-year study to determine their effects on EWM. These chemicals, he said, were found to be very effective in treating that invasive specie in Minocqua and Kawaguesaga lakes, where the chemicals were used in 2019. However, those same chemicals were ineffective in treating the EWM in Tomahawk Lake.
"We spent $55,000 of our reserve funds on this chemical treatment and at the end of the day it had absolutely zero impact on EWM in Lake Tomahawk," he said.
Lottig said the hypothesis for the reasoning behind this was due to the size of Tomahawk Lake as compared to the Minocqua and Kawaguesaga as well as the fact that EWM beds in Tomahawk Lake are long and narrow, usually bordering deep water. This led Lottig to believe the deep water diluted the chemicals which would then not penetrate the EWM in Tomahawk Lake as they did in the others.
Currently, Lottig said, harvesting boats are working on the lake in the dense EWM beds. With the help of Onterra Ecological Services, they are working on an integrated five-year plant management plan, which will be shared with stakeholders in 2022.
In his executive summary, Lottig revealed what he called "reassuring news." DNR lakes biologists, he said, have determined that over 90% of the lake is not suitable for EWM to grow. He said he also believes there were few areas left on Tomahawk Lake for EWM to colonize or grow. This means, he indicated, the EWM problems on the lake should not get worse. In fact, he said, there were reasons to believe it may improve.
First, he said, the Association's 2021 summer harvest schedule was the most ambitious yet, with over 100 acres of EWM to be harvested over the course of the summer. In areas where harvesting has occurred for the past three years, decreased densities of the invasive species were being seen.
Onterra biologists are currently conducting comprehensive studies on the lake. These studies include bottom type and water depth at which plants are growing. This work, Lottig said, will be followed by a high resolution EWM study this fall. Both surveys will help inform the Tomahawk Lake Association on the most effective and efficient ways to combat EWM on the lake for the next five years. Lottig said he looked forward to sharing the results of the work with those interested and expected that to happen in 2022.
According to Lottig, the DNR believes that harvesting of EWM is effective at removing dense beds in the lake and is likely the most effective approach. This approach allows TLA to fight this invasive species without putting chemicals into the lake year after year, as it has in the past with 2,4-D.
This year's EWM problem was exacerbated by a few factors, Lottig said. The first of those was the early ice out. This year saw the earliest ice out on Lake Tomahawk in four decades, he said. It was also a warm spring. That, coupled with unusually sunny summer weather, made for perfect growing conditions for EWM in Tomahawk Lake.
So far this year, TLW members have donated approximately $70,000 to the lake projects, Lottig said. This comprises approximately 45% of the budget. The remaining $80,000 of that budget is given to the TLA through township and government grants for a total of $150,000.
Lottig said only one in four property owners on the lake are TLA members. He called for those who are members to reach out to friends and neighbors who may not yet be members to encourage them to help in the fight against EWM on the lake.
Lottig, who has a background as a research scientist focusing on water quality in lakes, lives full time with his family on Tomahawk Lake. In his recent update, he assured stakeholders he would "turn over every stone" to find ways to minimize and control EWM on Tomahawk Lake.
Lottig's full update can be found on the Tomahawk Lake Association website www.tomahawklake.org.
Beckie Gaskill may be reached via email at [email protected].
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