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Idaho Department of Agriculture details expanded 2024 response to quagga mussels on the Mid‑Snake River
Summary
Agency leaders from the Idaho State Department of Agriculture told the Senate Agriculture Committee they doubled sampling statewide and mounted an expanded chemical response after quagga mussel veligers were detected on the Mid‑Snake River in 2024.
Agency leaders from the Idaho State Department of Agriculture (ISDA) told the Senate Agriculture Committee they expanded monitoring and mounted an aggressive, multi‑partner response after small numbers of quagga mussel veligers were detected in the Mid‑Snake River in 2024.
Chanel Tewall, director of the Idaho State Department of Agriculture, told the committee the department’s efforts are grounded in state law and described three public takeaways: the state’s Invasive Species Act (2008) directs the program’s work; Idaho has taken actions other states or federal agencies would not; and the department intends to “marry the best available science and the best data we can with common sense” in its response.
Nick Zervflo (Bureau Chief, Invasive Species Program, Idaho State Department of Agriculture) described the department’s technical work: ISDA doubled its sampling statewide, increased watercraft inspections by about 50%, and added labs and redundancy for molecular confirmation and blinded visual review. Zervflo said the program used environmental DNA (eDNA) carefully — noting eDNA can detect DNA from nonviable mussels and therefore requires follow-up sampling to confirm live infestations.
When small numbers of veligers were confirmed in 2024, the department initiated a rapid response and implemented an expanded chemical treatment from Oct. 8 to Oct. 19, 2024. The treatment used a chelated-copper product (manufactured by SePRO, marketed as Natrix) at a labeled target concentration of 1 part per million and the team maintained that concentration before starting a 200‑hour treatment clock; ISDA reported approximately 63,000 gallons of product were applied. ISDA said it worked with the manufacturer, a national contractor, local partners including Simplot for product logistics, Idaho Power and federal agencies (U.S. EPA, U.S. Fish and Wildlife Service, and FERC) to coordinate the treatment and monitoring.
Officials described the treatment as unusual in scale for North America and said it required specialized tactics (applicator totes, barges, helicopter slinging in one section) and substantial interagency cooperation. ISDA said copper concentrations returned to below baseline by about Nov. 8, 2024, and that monitoring would resume in spring (anticipated May–June) when water temperatures reach spawning range and make veliger detection reliable.
Committee members pressed ISDA on follow-up plans and risk. Director Tewall said the agency’s goal is to avoid recurring treatments but to remain ready to act if monitoring in 2025 shows ongoing reproduction or additional detections. Senators thanked ISDA for transparency and the interagency response; ISDA encouraged the public to use its website to view sample locations, dates and lab results.
ISDA emphasized the program’s statutory basis and said the state intends to continue sampling, public outreach and partnership-building to reduce the chance of spread via watercraft ballast and trailers.
