Laramie mosquito treatment delayed to June 17 over supply issues
A supply-chain delay pushed Laramie’s granular Bti mosquito treatment from June 10 to June 17, leaving another week for larvae in rural edges of town. The city says the work targets canal and floodplain areas before summer bite pressure builds.
Rural mosquito breeding grounds around Laramie will wait another week for treatment after the city moved its granular larvicide application from June 10 to Wednesday, June 17 because the product did not arrive on time. The delay matters along the Big Laramie River, the Big Laramie flood plain, and irrigated ground north and west of town, where mosquito pressure can rise quickly as yards, trails, and outdoor gathering spots fill up for summer.
The City of Laramie said the aerial application will use Bacillus thuringensis israelensis, or Bti, a bacteria commonly used to target insect larvae. City materials say the treatment is aimed at both nuisance and vector mosquito larvae, and it is not expected to harm fish, amphibians, livestock, or other aquatic invertebrates. For Albany County residents who live near irrigation ditches, creeks, and low-lying floodplain areas, that makes the work part public health measure and part land-management task.
The city’s treatment areas include irrigated acreages along the Big Laramie River southwest of the city, flooded riparian zones in the Big Laramie flood plain southwest and north of Laramie, and acreages north and west of town irrigated by the North Canal and Pioneer Canal. The city said staff chose the timing based on previous data and site inspections. Larval control operations began in April and will continue through the 2026 season.
The postponement lands as the city heads into a mosquito season shaped by West Nile risk monitoring. As of June 10, Laramie listed the 2026 West Nile virus risk at Level 1, or low risk, with zero Culex tarsalis pools tested and zero positive pools on the RAMP platform. The Wyoming Department of Health says West Nile has been detected in every county in Wyoming, most infected people have no symptoms, about 1 in 5 develop fever and other symptoms, and less than 1 percent develop serious neurologic illness.
Laramie’s mosquito records show why the city is treating the season as a recurring public-health issue rather than a one-time nuisance response. In 2025, the city tested 146 Culex tarsalis pools and found 30 positive for West Nile. The city reported 23 tested and nine positive in 2024, 262 tested and 25 positive in 2023, 41 tested and one positive in 2022, and 117 tested and four positive in 2021. City council also backed the 2026 control effort on Feb. 17 by approving Resolution 2026-20 for a $45,940 grant application, with an equal $45,940 in matching funds from the mosquito control budget.
The city’s broader plan still runs on a set schedule: larval control starts in spring, adult fogging begins when action thresholds are met, and spraying is done Sunday through Thursday when weather allows across the North, South/APO, and West zones. Fogging can be suspended if wind tops 10 mph, temperatures fall below 50 degrees, or rain is falling, leaving the June 17 larvicide flight as the next key step in keeping mosquito pressure down before the season peaks.
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