Idaho agriculture officials describe expanded 2024 quagga mussel monitoring and treatment on the Snake River

Chanel Tewalt, director of the Idaho State Department of Agriculture, and Nick Zerflue, bureau chief overseeing aquatic invasive species work, told the House Agriculture Affairs Committee the agency substantially expanded inspections, water sampling and partner support in 2024 after quagga mussel veligers were found on the Snake River.

Tewalt said Idaho increased boat inspections by about 50% and doubled statewide water sampling from 2023 to 2024 and that the agency added laboratory and subject‑matter experts to ensure confirmation of findings. "We have increased by every single measure what we do in this program," she said to the committee.

The nut graf: state officials described a multi‑layered approach — visual identification, molecular confirmation and carefully applied eDNA — and said detection of any veligers in the Snake River required rapid delimiting, permitting and a treatment plan coordinated with federal and local partners.

Tewalt described the 2023 treatment (Twin Falls to Centennial Park) and a larger 2024 response after veligers were detected again in September 2024 upriver of Twin Falls Dam in the Mid‑Snake. Agency staff emphasized the small numbers found in 2024 compared with 2023, noting that even a handful of veligers are biologically significant because individual mussels can produce thousands of eggs. Tewalt and Zerflue described steps to avoid false positives, including double‑blind image review and multiple laboratory confirmations, and said eDNA is being used carefully to guide follow‑up rather than as the sole basis for action.

Zerflue described the department’s delimit sampling approach for a river environment: methodical plankton‑net sampling upstream and downstream of detection locations, strict decontamination of equipment and duplication of laboratory analysis through multiple labs and external experts. He said the agency observed no adult mussels in 2024 and that the detections appear to represent a very small population, a position that creates an opportunity for aggressive response toward eradication.

The department described a treatment on the Mid‑Snake that used a matrix chelated copper product applied to achieve and maintain 1 part per million for an extended contact period — the agency said the 2024 treatment targeted an extended 200‑hour contact time and used roughly 60,000 gallons of product deployed via metered totes and applicator boats between Oct. 8 and Oct. 19. The agency said it coordinated permitting and hydro operations with Idaho Power, U.S. Fish and Wildlife Service, the Idaho Office of Species Conservation and the Idaho Department of Water Resources to control flows and monitor downstream effects on listed species; contingency measures including activated charcoal were staged but not deployed.

Officials highlighted the operational complexity: deep pools, springs and remote reaches; the need to ensure enough product was available; and the importance of partners such as Clean Lakes (applicator contractor), SePRO (manufacturer) and Simplot (local distributor). Zerflue said the operation required intensive field work over several weeks, daily safety briefings and a large team of state and contracted personnel. Tewalt and Zerflue credited state, local and private partners for rapid deployment and said they had pledged continued vigilance across the state’s waterways.

Ending: Committee members asked about enforcement of out‑of‑state boater rules, station staffing at key border crossings and the long‑term balance between inspections and watershed treatments; agency officials said the state has legal authority to inspect and act but that preventing introductions will require law‑enforcement and community cooperation in addition to continued monitoring and contingency planning.