Green invasion hits Orcas Island’s Cascade Lake - Salish Current

Orcas Island rowing enthusiast Gina Culbert pulls a mass of invasive Eurasian watermilfoil out of Moran State Park’s Cascade Lake. Milfoil shades out native aquatic plants, harms the ecosystem and degrades boating, fishing and swimming. Cascade Lake is the domestic water supply for hundreds of residences in Orcas Island’s Rosario district. Moran State Park officials are seeking permits for control strategies including treatment with herbicidal compounds. (Toby Cooper / Salish Current © 2024)


Eurasian milfoil threatens domestic water source and state park’s aquatic gem

Updated July 15, 2024

Eurasian watermilfoil — a fast-growing, non-native aquatic plant that threatens the natural freshwater ecosystems, human recreation and domestic water infrastructure — has infested Orcas Island’s Cascade Lake, prompting the Washington State Parks authority to seek permits for control. 

The popular lake in Moran State Park doubles as the domestic water source for hundreds of households in Orcas Island’s Rosario district and the destination of choice for many of the park’s 900,000 yearly visitors. Unchecked milfoil threatens both, and the park’s administrators must decide how to protect the habitat.

Water administrators in Washington have a standing permit that allows them to assess and authorize control measures for invasive aquatic plants, explained Shawn Ultican, the designated permit officer at the Washington State Department of Ecology who is handling the park’s application. 

Under that umbrella authorization established by the federal Clean Water Act and the Water Pollution Control Act, Moran has been granted a coverage permit as of July 1. It gives Moran State Park an immediate war chest — up to $75,000 in a matching grant account — with which to design a specific battle plan against Cascade Lake’s invasive milfoil. [Correction: Moran has received $75,000 in state grant funding to design a specific battle plan with which to apply for a permit to attack Cascade Lake’s invasive milfoil.]

Moran State Park takes the lead

Lizbeth Seebacher, Northwest Region Steward for Washington State Parks, is charged with managing the mitigation program. “I am leading the way,” she said, and she and Wes Glisson of the Washington Department of Ecology found Eurasian watermilfoil in lake the last summer.

The 2023 biological survey — the first in the park since 1997 — sought data on heavy metal contamination in fish. Instead, they found milfoil. Seebacher knew they had to act. “We all care deeply about the resource,” she said.

Watercraft of any sort and even fishing tackle or footgear can introduce or spread piggybacking invasives such as milfoil and certain types of mussels, but outboard motors and trailers are by far the most significant means of transport. A team inspects a motorized craft at Lake Whatcom in Bellingham. (Courtesy CoB)

“As we go forward, Lizbeth will be selecting from alternatives and receiving public comment,” said Glisson from Ecology’s Olympia headquarters. [Correction: Ecology has not yet received a permit application as of July 15.]

Seebacher’s alternatives, together called “integrated pest management,” include physical removal by hand harvesting, public education, biological controls and the use of chemical herbicides. 

The invasive sort

The San Juan County Noxious Weed Control Program lists native milfoils of several species as occurring in local freshwater lakes. Not all are a problem. 

The invasive species including M. spicatum were accidentally introduced into North America. Once established in a freshwater lake, milfoil spreads aggressively, forming dense floating mats, impacting fishing, swimming and boating, and shading out native aquatic vegetation. 

As milfoil out-competes native plants, the whole aquatic ecosystem is at risk. Seebacher agreed the plant’s growth can be “explosive.” 

Milfoil spreads easily from lake to lake on the hulls of boats, motors, fishing tackle, footgear or anything people carry with them. “Any tiny fragment immediately grows into another plant,” said Jason Ontjes of the noxious weed control program. “It continues to spread from there.”

Your drinking water

Dan Burke, general manager of the Eastsound Water Users Association (EWUA), confirmed that Cascade Lake supplies drinking water for 500-odd households in the Rosario district, plus Rosario Resort. The EWUA is the billing agent for Washington Water, which, along with Rosario Resort and certain private parties, owns the water rights.

Burke is aware of the need for milfoil controls. “We are seeking details on the park’s control strategy,” he said.

“Approvals by all water rights holders are needed as a condition of the permit,” said Seebacher. “The public will be notified and comments received during this process, as required by our permit.”

A preferred herbicide

The preferred alternative for herbicidal treatment in the park’s Cascade Lake permit is ProsellaCOR, the trade name for florpyrauxifen-benzyl, a systemic herbicide that is taken up by aquatic plants. 

According to a 2018 fact sheet issued by the Wisconsin Department of Natural Resources, florpyrauxifen-benzyl mimics the plant growth hormone auxin that causes excessive elongation of plant cells that ultimately kills the plant. 

The compound’s half-life — meaning the rolling time it takes for one half of the chemical to decompose — is listed as 1 to 6 days. Decomposition is slower under low sunlight or cloudy water conditions.

Ontjes indicated that ProsellaCOR can be handled only by trained techs. Dave Heimer, noxious weed control coordinator at the state Department of Fish and Wildlife, is a qualified specialist. “We are here if they need us,” he said.

Ecology’s Ultican pointed to the department’s 2017 Final Supplemental Environmental Impact Statement for Aquatic Plant and Algae Management as the data source for the safety and efficacy of ProsellaCOR.

The relevant section states that “based on the current understanding of available environmental fate, chemistry, toxicological and other data, there is little to no cause for concern to human health or ecotoxicity for acute, chronic or sub-chronic exposures to ProcellaCOR formulations.”

Similar language can be found addressing ProsellaCOR’s effects on fish, birds, and other wildlife. 

In 2017, shortly after the issuance of the omnibus final EIS, the EPA approved ProsellaCOR for use in sources of public drinking water. In 2019, DOE independently approved it for statewide use.

“The use of aquatic herbicides can trigger concerns,” Ultican said regarding the prospect of a team moving about Cascade Lake in protective gear. “I get that.”

Still, he noted that ProsellaCOR has been used in about 35 lakes around the state since the 2019 approval. He cited applications at Lake Vancouver in Clark County and American Lake in Pierce County.

Loving Cascade Lake

Orcas residents and visitors flock to Cascade Lake, seeking water recreation, fishing, hiking on the perimeter trail or simply basking in island tranquility. 

Incoming boaters at launch sites on Lake Whatcom are required to pass a knowledge test, and every boat is inspected. The program is jointly sponsored by Whatcom County and the City of Bellingham. Area noxious weed control boards are in favor of such a program at Cascade and Mountain lakes in Moran State Park. (Courtesy CoB)

“I am definitely concerned about the use of chemical controls,” said Barbara Nesbet, a member of the local rowing club. “I love the lake not only for its beauty, recreational opportunities and wildlife, but also as our water supply.” She shared her fears that the long-term effects of ProsellaCOR have not yet been evaluated. 

Nesbet recalled the tumultuous history at New York’s Lake George — many times larger than Cascade at 32 miles in length — where plans for herbicidal milfoil controls have been hamstrung by years of public debate and litigation. 

Lacking approval to use ProsellaCOR, the Lake George Parks Commission spends $500,000 per year on hand removal of milfoil. 

A matter of inspection

By far the most efficient and cost-effective way to manage milfoil is to keep it from becoming established in the first place. 

Whatcom County and the City of Bellingham jointly sponsor a public education and invasive species boat inspection program at lakes Whatcom and Samish.

Since invasive zebra mussels, quagga mussels and milfoil spread almost exclusively by hitchhiking, boat inspections are the best preventive medicine. 

Considering the foreve cost of chemical and/or physical controls, Whatcom County sees a clear economic advantage to public education and inspections, which are paid for out of public works budgets. 

“Every boat and every trailer coming to these lakes is inspected, and every boat owner must take an annual knowledge test,” said team leader Kyle Lang. “The public has embraced the program. They know how destructive these invasives can be to the lakes.”

Glisson and Ultican at Ecology, Ontjes at San Juan County and Davidson and Seebacher at State Parks all appreciate the value of boat ramp inspections. “So far, no milfoil has been found in Mountain Lake,” said Seebacher of the upper lake in Moran State Park. “We want to keep it that way. The best hope is to start an inspection.”

“I believe I have found a source of grant money for such a program,” added Davidson. “Something to work on, for sure.”

— By Toby Cooper

Also read in Salish Current: “Giant hornet effort approaches milestone as another pest shows up,” Feb. 26, 2024

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