Watershed advisory group urges coordinated five-year strategy for Payette Lake milfoil control; ISDA to report to WAG Aug. 26

Members of the Big Payette Lake Watershed Advisory Group (WAG) briefed Valley County commissioners on efforts to update the 1998 lake management plan and to develop a coordinated strategy for controlling Eurasian watermilfoil.

"WAG believes that a comprehensive and integrated Eurasian watermilfoil control strategy thoughtfully considers relevant issues and is based on objective information and sound decision making," Dave Simmons, a WAG member, read from a prepared statement and said. Simmons, who leads the WAG tech committee, summarized the group’s review of historical efforts and recent changes in agency responsibilities.

Simmons told the board that Chapter 12 of the 1998 plan (adopted following a governor-appointed council and legislative action) discouraged herbicide use at that time because of drinking-water reliance on Payette Lake, and that Valley County’s weed department ran a diver-assisted mechanical removal program from about 2008 to 2021. In 2022 the Idaho State Department of Agriculture (ISDA) assumed responsibility for the effort, Simmons said. WAG members were first convened in March 2025 to advise the Idaho Department of Environmental Quality (IDEQ) on an updated plan.

WAG told commissioners it is awaiting ISDA’s current milfoil survey results and noted ISDA removed an eight-acre test plot near North Beach for herbicide testing this year. Simmons and other WAG members emphasized the need for updated nearshore water-quality monitoring and for a planning process that incorporates local knowledge and agency resources.

Commissioners and WAG members discussed control methods. Simmons said mechanical diver-assisted pulling performed well for many years but that available diver capacity and funding have declined. He said newer chemical options — including a trade name referenced in the discussion, Procellacor — are in use elsewhere and have some short-term tests but limited long-term studies. "It behooves us to just be very cautious when we're talking about putting herbicides into a public water source," Simmons said, citing the lake’s role as a domestic water supply for many homes.

Commissioner Mappin proposed collaborating with ISDA on a five-year control plan; WAG members indicated they had not seen a Payette Lake-specific five-year plan from ISDA but said such a plan would be useful. WAG chair Deb Faraday confirmed ISDA staff (including deputy director Lloyd Knight, Jeremy Varley and Andrea Thompson) will attend the WAG meeting on Aug. 26 at 10:00 a.m. and that WAG plans to compile guided questions in advance to make that meeting productive.

Faraday invited commissioners to a pontoon-boat site visit on Payette Lake to view testing sites and nearshore conditions; commissioners said they would check open-meetings requirements before attending. Valley County also indicated it has budgeted $35,000 for milfoil eradication for the next fiscal year and that some funds remain available in the current year.

WAG and commissioners discussed forming a task force that could include ISDA, IDEQ, Valley County and the City of McCall, and possible investments in mechanical harvesting tools as part of a combined approach. No formal county action was taken at the meeting; WAG will continue coordinating with ISDA and will report back after the Aug. 26 meeting.

A summary of next steps shared at the meeting: ISDA to present survey and test-plot findings to WAG on Aug. 26; WAG to provide a list of guided questions to ISDA in advance; county staff to consider local resource needs including potential equipment purchases and budget lines.