Mosquito Control

Welcome to the DEH’s Mosquito Control Program website!  Click on the links below for information on mosquitoes, the City’s Mosquito Control Program, and how to protect yourself from mosquito bites and mosquito-borne diseases.

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We recognize that mosquitoes are a nuisance and can be especially active in neighborhoods that are near waterways and natural areas. Here's what we're doing to keep mosquito populations in Denver low and protect public health:  

The city does not spray or contract for the spraying of adult mosquitoes.

Locations where DEH monitors, treats and traps mosquitoes are shown in the map below. The map is regularly updated with information and results from our monitoring and treatment efforts.

You can protect yourself and your neighbors from mosquito bites in two ways – through prevention and elimination of stagnant water where mosquitoes breed:

Prevention Tips

  • Limit activity outdoors at dusk and dawn
  • Wear protective clothing like pants and long sleeves when outdoors
  • Wear mosquito repellant containing lemon eucalyptus oil, DEET, picaridian, or IR3535
  • For more information on insect repellants, visit EPA’s website.   

Eliminate Mosquito Breeding Sites

  • Remove water from containers, tires, birdbaths, gutters, and buckets around your home 
  • To be effective, water needs to be removed weekly since it only takes 3 to 7 days for mosquito eggs to hatch.
  • Do not overwater your yard, as it can create standing water in gutters and storm sewers.
  • Properly maintain fountains and swimming pools, or drain and cover if not in use. 


For more information on how to protect yourself from mosquito bites visit Fight the Bite Colorado or download the American Mosquito Control Association’s fact sheet on mosquito prevention and protection

Contact Us

Got an issue you can’t resolve?  Call us at 3-1-1 (720-913-1311 if outside the Denver area) or visit the 3-1-1 website to see if we can help.

Denver traps and collects adult mosquitoes at 5 sites across the city to determine if West Nile Virus (WNV) is present in our local mosquito populations. The mosquitoes are sorted by species to identify the ones that are most likely to carry WNV. Those samples are then sent to the Colorado Department of Public Health and the Environment to test for the virus.

Test Results

  • In 2014, Denver has submitted three sets of samples collected 8/18/14, and 9/2/14.  
  • The 8/18/14 set included three sub-samples which contained a total of 104 mosquitoes to be tested.  The results were positive for WNV for one of the three sub-samples.  The positive result was from a sub-sample that contained 27 mosquitoes. This means that at least 1 mosquito in the sample carried WNV, but that none of those in the other two (77 mosquitoes) were infected.
  • Samples collected on 8/25/14, contained a total of 68 mosquitoes, for which results were negative for WNV.
  • The 9/2/14 set included 2 sub-samples (total of 70 mosquitoes) which were negative for WNV.


While the positive result for WNV was not unprecedented in Denver, the last positive test occurred in 2007.  It is important to point out that testing of adult mosquitoes did not occur in 2012 and 2013 in Denver.

Data for nearby counties indicates that WNV has been found in adult mosquitoes throughout the region this year, particularly north of Denver along the front range. 

The number of Culex species (those most likely to carry WNV) collected in the Denver traps is comparable, or lower than what was found in nearby counties (Adams, Arapahoe, Boulder, Jefferson).

What does this mean for you?

While the risk of exposure to WNV is low, you should still protect yourself.  Mosquitoes generally remain active through September or until colder nights (e.g. 40’s) set in.  See “Protect Yourself from Mosquito Bites” for more information.

Learn more about mosquitoes here.

Larvicide Locations Map

How to use this map: Clicking on the icons on the map will open up a window with a description of the site, and information from the most recent site visit.

Icons are located where:

  • Populations of larval (juvenile) mosquitoes are monitored;
  • Larvicides (a biological pesticide that targets larval mosquitoes) are applied when needed, and;
  • Adult mosquitoes are trapped (caught) for identification and testing for West Nile Virus.

Note that information related to the most recent site visit may not be representative of current conditions.