Serving Colorado's Counties

Technical Update vol. 25 no. 28 - Avoiding Mosquitoes

July 13, 2021

Colorado’s recent wet Spring did more than fill rivers and streams; it also created the perfect breeding conditions for mosquitoes. More than just a biting nuisance, mosquitoes can spread diseases like the West Nile Virus, a type of encephalitis (swelling of the brain), first identified in the United States in 1999. According to the Department of Bioagricultural Sciences and Pest Management at Colorado State University, the first recorded case of West Nile Virus in Colorado was in 2002.

 Mosquito Life Cycle

 Mosquitoes breed in standing water. An adult female lays about 100-400 eggs in clusters called rafts that float on top of the water. Eggs hatch in 2-3 days producing larvae, also knows as wigglers. The larval stage is followed by a pupa stage that goes through several molts before an adult mosquito emerges. Only female mosquitoes feed on blood. The males feed on plant juices.

Preventing Mosquitoes

Because mosquitoes need standing water to breed, one of the most effective ways to control their population is by eliminating those sources. Mosquitoes can lay eggs in less than one ounce of water. The recent wet Spring and Summer means that anything outside (e.g., old tires, empty planters, cans, puddles, etc.) that holds water may provide an opportunity for mosquitoes to lay their eggs. It is crucial to evaluate your environment for potential breeding grounds.

Preventing Bites

 While eliminating standing sources of water can reduce the mosquito population, it does not protect against mosquitoes already present. Female mosquitoes are attracted to body heat and carbon monoxide produced when exhaling. They have a strong sense of smell and are drawn to floral perfumes and sweat. They are most active at dawn and dusk and prefer shaded areas. They also tend to be drawn to dark clothing.

The Centers for Disease Control provides the following tips to help prevent being bitten.

  • Use insect repellent: When used as directed, Environmental Protection Agency (EPA)-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women. Use an EPA-registered insect repellent with one of the following active ingredients: DEET, Picaridin, IR3535, Oil of lemon eucalyptus (OLE), Para-menthane-diol (PMD), 2-undecanone.
  • Cover up: Wear long-sleeved shirts and long pants.
  • Treat items such as boots, pants, socks, and tents with permethrin or purchase permethrin-treated clothing and gear. Do not apply permethrin directly to the skin.

What This Means for Counties

 For anyone who works outside, especially in wooded areas, mosquitoes are unavoidable. However, taking precautions such as wearing light long-sleeved clothing, using mosquito repellent, and avoiding being outdoors during peak mosquito activity, can limit the bite risk. For more information about preventing mosquito bites, visit

A PDF of this Technical Update is available here.

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