Mosquito Control

VDCI (Vector Disease Control International), the City’s contractor for adult mosquito control, conducts their operations based on specific criteria. ULV adult mosquito control commences within the City when:

• Mosquitos found in traps strategically placed throughout the City reach more than 150 mosquitoes
• AND
• A positive identification of West Nile Virus is found in a mosquito within the three-county area of Weld, Larimer and Boulder Counties.

There are no biological control alternatives approved for large-scale adult mosquito control operations at this time.

VDCI uses specialized Ultra-Low Volume (ULV) equipment to control adult mosquitoes. This is conducted with a synthetic pyrethroid treatment, permethrin (commonly found in flea and tick shampoos). Permethrin is a man-made version of a natural insecticide derived from a type of chrysanthemum plant. Permethrin is one of the least-toxic products registered with the U.S. EPA and the State of Colorado for public health mosquito control applications.

The chemical used is permethrin. It is a synthetic version of pyrethrin which is derived from plants in the chrysanthemum family. This is a much less toxic insecticide that poses significantly less risk to people and the environment than those used around the world in the past such as organophosphates and DDT.

The rate used is also much less than the maximum allowed by the label which makes the application targeted to mosquitoes while minimizing effects on larger insects. About 0.0035 lbs. or about half an ounce of permethrin are applied over an acre (about the size of a football field) which means that the average residential property is exposed to less than 0.0007 lbs. of permethrin in an application. For reference, head lice shampoos that contain permethrin suggest 0.06 lbs (1-2 ounces) be applied directly to a child’s scalp every 9 days.

The spraying is also done using an ultra-low volume fog with droplets less than ½ the diameter of a human hair that is targeted to mosquitoes, breaks down rapidly in the environment, exhibits minimal deposition, and does not bio-accumulate in the environment.

We further protect non-target insects by spraying in the evening when most other insects are not active.

Please note that spraying is conducted dusk until dawn when honeybees are in their hives, limiting their exposure when spraying occurs. In addition:

• Residents can request that the contractor shut off spraying when they drive past their residence by filling out the form at the bottom of this page: vdci.net/colorado or by calling 877-276-4306.
• If possible, hives could be moved to areas further away from roads where the spray truck would drive.
• Block the hive entrance with a hive entrance reducer so that bees don’t come out during spraying and then remove to let the bees out first thing in the morning.
• Cover hives with cloth like wet burlap to protect from direct contact with the spray. Extreme caution should be taken when doing this as it is possible to restrict air flow and cause the hive to overheat. Do not wrap tightly and try to tent the covering. Remove once spraying is complete.