Snake River Quagga Mussel Treatment Conclusion Update

The ISDA has completed its 2026 Snake River Treatment for quagga mussels. The 2026 treatment was a multi-phase project that utilized the copper products Natrix, Earthtec QZ and Cutrine Plus Granular. The treatment began Thursday, August 27, and concluded Wednesday, September 16.  

ISDA confirmed, Tuesday, August 18, 2026, a detection of quagga mussels in the infested area of the Snake River. Sampling has shown a 77% reduction in quagga mussel detection in the Snake River near Twin Falls. The results show significant progress and demonstrate the effectiveness of ISDA’s ongoing treatment strategy. View the full treatment plan below. 

The treatment application went according to ISDA’s 2026 plan, which accounted for complex factors, including deep holes, freshwater inputs and varying conditions such as temperature changes. Copper levels and treatment impacts continue to be closely monitored by ISDA staff, the contracted applicator, and the product manufacturer. What was new to the treatment application this year was the decreased surface area impacted. ISDA and its partners utilized the placement of totes on barges at strategic locations with deep-hole injection equipment designed to target any potential safe harbors. 

What is the treatment? 

• The treatment utilized Natrix, Earthtec QZ and Cutrine Plus Granular. 

• Natrix has been used in the Snake River quagga mussel treatments in 2023, 2024, and 2025, which significantly reduced the quagga mussel population. 

• Earthtec QZ is another copper-based product that has a different formulation intended to address potential safe harbors in the infested area that may have quagga mussels. 

• Cutrine Plus Granular was deployed in mesh bags at targeted fissures harboring quagga mussels. The bags were deployed for 96 hours and were removed following the conclusion of the treatment.  

• Natrix, Earthtec QZ and Cutrine Plus Granular are copper-based products that are labeled and approved by EPA for this type of aquatic application. The products have been used in other states for mussel, fish, algae and plant control. 

• The application rate of the products was designed to kill mussels while remaining below the drinking water standard for humans. 

• Copper is naturally occurring in this system. The treatment products dissipate downstream and are expected to dissipate within days after the final application 

• River copper levels are expected to return to normal within 25 miles, near the Highway 46 Bridge. 
• ISDA and the Idaho Department of Environmental Quality monitored the river to evaluate treatment effectiveness and copper dissipation. ISDA had mitigation efforts in place to deploy if additional copper was detected downstream. 

Treatment Impact  

• Treatment application occurred across two individual target locations of the river in efforts to eradicate quagga mussels at all life stages.  

• The labels for the products used indicate no impact on any drinking water sources. The application rate of Natrix, Earthtec QZ and Cutrine Plus Granular at the immediate application site was lower than the drinking water standard. There were no public drinking water intakes near the treatment area of the Snake River.  
• The treatment caused minimal mortality in fish, aquatic plants and algae from Sage View downstream to Highway 46 Bridge.  

Snake River Closure  

As of Friday, September 18, there are no active closures on the river.  

The copper-based treatment was applied at a rate below the drinking water standard. While staying out of the dissipation area was not required by the product label, out of an abundance of caution, ISDA recommended that the public keep out of the area, including livestock and pets, between Hansen Bridge and Highway 46 Bridge from Thursday, August 27, through Friday, September 18. 

 

Media Contact:

Stevie Harris

Deputy Director

(208) 332-8552

media@isda.idaho.gov