Scientists to examine best mosquito control methods

Gunnison County will fund two studies

Gunnison County will fund two projects to monitor and research the impact of insecticide-based mosquito control on water quality and aquatic insects this summer.

The first study will be led by Kevin Alexander, a professor of biology and environmental studies at Western State Colorado University, and will assess the role of the insecticide permethrin on aquatic insect die-offs. Die-offs have been observed along local streams and may be an indication that permethrin is entering local waterways through aerial drift.
“[This] may be causing the reduction of aquatic insect populations in affected streams,” wrote Alexander in a proposal for the study to the Gunnison Board of County Commissioners. “A reduction in these aquatic insects can have negative impacts on the entire stream ecosystem and stream productivity. A substantial decline of aquatic macro invertebrates is harmful to trout, birds, wildlife and aquatic vegetation.”
Permethrin is a broad-spectrum insecticide used to kill a variety of insects at all life stages by paralyzing their nervous systems. It has been shown to be highly toxic to fish in laboratory studies, and according to the Extension Toxicology Network aquatic ecosystems are particularly vulnerable to its effects.
Alexander will study insect populations in areas near aerial spraying locations both before and after spraying occurs to determine any changes in population health.
The second study will be conducted by Colorado Parks and Wildlife and will focus on water quality. The agency will collect samples of water in areas where spraying is slated to occur and will work to determine how much, if any, insecticide enters waterways.
“We signed a contract with Colorado Mosquito Control, Inc. to control for mosquitoes in the county,” said Gunnison County manager Matthew Birnie. “We will be using the research and findings produced in the solicited studies as guidelines in the contract.”
Spraying for mosquitoes will likely begin in June, with peak management occurring in July. Backpack and hand sprayers are the primary means of the insecticide delivery; however, the county does contract for one large aerial spraying.
“It is a relatively benign larvicide used and we will time the aerial spraying with water levels and weather,” said Birnie. “Research will be happening as spraying is happening.”