The Idaho State Department of Agriculture on Feb. 24 started a follow-up treatment for invasive quagga mussels on part of the Middle Snake River.

The treatment with potash, or potassium chloride, focuses on deep pools near waterfalls and rocky areas. The still-water pools are isolated from the main channel after high water recedes seasonally.

Quagga and zebra mussels can clog irrigation, drinking water hydroelectric power systems — causing significant economic loss — and can alter aquatic environments.

ISDA and partners treated the river section with chelated copper following the first detection of quagga mussels in 2023 and after a smaller-scale detection last year. The isolated pools were included in the treatments.

The current treatment reflects the department’s commitment to use “every available tool” to combat quagga mussels, according to a news release. Potash will be used in the still-water pools “as an extra measure toward eradication of the mussels.”

Potash, a commonly used fertilizer, is shown to be relatively safe for native aquatic life including fish, according to the department. For mussels, which absorb potassium from water, it interferes with regulation of cellular processes and can cause death in as little as two days.

The U.S. Environmental Protection Agency authorized the potash treatment plan. The process involved assessment of potential risks to human health and the environment, including confirmation that use as a pesticide meets required safety standards, according to ISDA. The department worked with EPA, other agencies and the product manufacturer.

Potash has been used to treat for mussels in other U.S. water bodies.

Treatment is expected to take about 15 days, ISDA public information officer Sydney Kennedy told Capital Press. Monitoring will continue during and after treatment.

The current treatment is targeted to maximize overall eradication efforts and is much smaller — involving fewer people and less equipment — than previous treatments, she said.

Public access to the Twin Falls area of the Snake River is not impacted, according to ISDA. Inspection and decontamination of watercraft entering and exiting the river between Broken Bridge / Yingst Grade and Hansen Bridge remains mandatory.

Sampling for mussels and veligers, or larvae, will continue when water temperatures increase, Kennedy said.