ROGER DONEGAN | JANUARY 30, 2020
The end of January might find us paging through seed catalogs or deciding what to plant in the garden in 2020. Invasive plants and weeds don’t need any such stewardship. They simply take hold or pick up where they left off last season, as sunlight increases and temperatures rise. Eurasian watermilfoil, the invasive aquatic nuisance plant, has peaked in parts of Lake Iroquois, to one degree or another, in summer for decades now.
Two local weeklies renewed discussion on the EWM topic with articles last fall: “New Herbicide for Lake Iroquois” in The Williston Observer (Oct. 24, 2019) and “A Hinesburg Horror Story” in The Citizen (Nov. 19, 2019). Both articles flashed the same misleading 2016 file photos and announced the Lake Iroquois Association, and Williston, plan to push a new aquatic nuisance control permit application in 2020, but with a twist. In the 2016 application, the herbicide of choice was Sonar (fluridone). In 2020 the selected herbicide is ProcellaCOR (florpyrauxifen-benzyl).
The 2016 aerial reconnaissance-like photos and captions don’t distinguish EWM from pond lily pads, areas of emergent arrowhead, or other entwined water weeds in the mixed mass, inferring the pictured scene as one huge EWM mess.
Displaying a short memory, neither article represented the timeline of the Sonar whole-lake herbicide application accurately. It’s a matter of record that Williston submitted that application in the fall of 2016. At Town Meeting Day in 2017, Hinesburg residents voice voted on an appropriation to the three-town Lake Iroquois Recreation District without knowledge of the plan in a would-be permit. The state officially denied the Sonar permit Oct. 15, 2018. The unprecedented delay and denial were attributed to the high volume of verbal and written responses received during the state public comment period for the permit application. On Oct. 27, 2017, the Burlington Free Press ran the article, “Lake Iroquois Invasive Milfoil Slows as Officials Consider Herbicide Permit.”
The experience touched off by the post-Town Meeting Day disclosure of the Sonar permit application left lasting impressions. Had the permit been granted, the five-year experiment with Sonar would still be in effect through 2021.
LIA’s step up to a more professional aquatic plant survey contractor and record keeper, as an improved lake monitoring tool, is to their credit. However, there remains built-in short sightedness in practice, as the report of the latest plant survey doesn’t present data beyond the previous survey which recently switched to a two-year instead of a three-year cycle. This is why we hear unsubstantiated raves of the latest herbicide treatment used in a litany of comparative lakes in-state but see nothing documenting long-term treatment histories, or the boom and bust growth cycle of EWM in those very same lakes.
Also, to the credit of the survey contractor, the October 2017 Vermont Department of Fish & Wildlife report incorporated the state’s 1972 topographical (water depths) image of Lake Iroquois showing the aquatic plant weed beds to be exactly where these reestablish each summer.
This past October, UVM’s online Center for Research on Vermont flagged the most recent DFW Lake Iroquois aquatic plant survey (September 2019 report) as showing a significant increase in EWM sample points but also noted a jump of in-lake plant species which is viewed as an indicator of good water quality. The Vermont Department of Health greenlighted ProcellaCOR use in the other lakes in 2019, but now specifically emphasizes mandatory near-time notification of applied herbicide for landowners, residents of the lake, and continuous “water mile” users downstream.
One won’t find a consumer protection report on ProcellaCOR. It is certainly not a consumer product but rather a highly regulated, Environmental Protection Agency–registered aquatic plant herbicide which comes with strict use requirements and a right-to-know safety data sheet. The detailed six-page product label for ProcellaCOR, unique for registered pesticides, includes three precautions worth mentioning in our local scenario. First, “Under certain conditions, treatment of aquatic weeds can result in oxygen depletion or loss due to decomposition of dead plants, which may cause fish suffocation.” In other words, ProcellaCOR just might mean trading one lump of rotting lake plants for another plus a fish kill in the north end of the lake. Second, regarding the chance of EWM developing resistance to the new herbicide, “Do not use ProcellaCOR alone in the same area for more than two consecutive years.” And thirdly, “Do not compost any plant material from treated area.” Regarding the latter, I bet many still remember the yearlong debacle in 2012 caused by persistent herbicides that turned up in commercially marketed compost products sold in Vermont.
The ProcellaCOR Safety Data Sheet, in plain language under a section titled “persistence and degradability,” says the material is expected to biodegrade very slowly in the environment. It’s stability in water with neutral pH and at a temperature of 77 Fahrenheit is given a half-life of 111 days. Herbicide considerations aside, I salute all other activities that LIA manages to accomplish year in and year out.