Boulder's innovative mosquito program uses a variety of tools and ecological data to protect people and the environment.

Although living with mosquitoes is a fact of life during the summer, community-wide efforts from both the city and residents can reduce mosquito numbers and decrease the risk for mosquito-borne illnesses like West Nile virus.

The city's innovative mosquito management program uses a combination of traditional mosquito management tools, as well as ecosystems protection and biodiversity surveys to manage mosquitoes. The city also samples and tests mosquitoes for West Nile virus to estimate risk fo the pubic. Residents also play an important role by reducing mosquito breeding habitat on private property and regularly employing measures to avoid mosquito bites.

An Ecological Approach

Of the 57 known species of mosquitoes in Colorado, about a dozen are routinely caught in city mosquito traps. Each of these species have different behaviors, host and breeding site preferences and inhabit complex ecosystems. Mosquito larvae compete with other species of mosquitoes and non-biting aquatic flies for resources and both the larval and adult forms are important food sources for an array of aquatic and terrestrial insects and other animals. When wetland ecosystems are in balance, mosquito numbers stay relatively low. The city studies the characteristics of wetlands that keep mosquitoes low and reduce the risk of disease transmission to people. Both adult and larval mosquitoes are regularly tracked and monitored. When mosquito larvae are not kept under control by predators, a larvicide is applied that targets and kills the mosquitoes. Learn more about the City’s Ecological Mosquito Management Program.

West Nile Virus

When West Nile virus (WNv) arrived in the Front Range in 2003, human cases reached epidemic levels in Colorado. Cases declined sharply in 2004, and although WNv is now endemic with cases occurring every year, it has not reached epidemic levels after 2003. Whenever mosquitoes are active, you should assume that West Nile virus is present and take precautions to protect yourself. Always inspect your property and drain standing water to prevent mosquito breeding near your home and within the community. The West Nile Virus Fact Sheet provides more information to keep you and your family safe.

Human West Nile Virus Cases in Boulder County from 2003-2021

What is the vector index and what does it mean? The vector index estimates risk to people of contracting WNv by calculating the abundance of Culex mosquitoes - the type of mosquito that can become infected with WNv - and the infection rate of WNv in mosquitoes. When the vector index reaches 0.75, the risk is considered high enough to warrant additional actions to search for any missed Culex breeding sites and to locate and drain any standing water. The city works with other agencies to coordinate information and communication.

Individuals are always advised to take protective measures to avoid mosquito bites and reduce Culex breeding on private property during every mosquito season, regardless of vector index results. As WNv risk increases, the city will increase communication and outreach to the community to provide information to keep people safe.

Weekly Mosquito Report

Report a Mosquito Concern

Report online

Submit an online report on:

  • Mosquito issues or concerns; and/or
  • Areas of stagnant water on city-owned properties.


Feel free to contact us to ask questions about mosquito management in general or to share ideas or feedback:

Boulder County residents

  • If you live outside the City of Boulder, visit the Boulder County Mosquito Control website for more information or contact Boulder County's hotline at 877-276-4306.