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Pests and pest control in Colorado

Pests to know in Colorado

Why each one matters here is cited in the sections below.

Pests documented in Colorado

From public GBIF occurrence records since 1990. A record means a species was documented in Colorado, not that it's common near you.

Many public records (577)

Fewer public records (154)

Range named by extension sources (3)

Invasive species reported here

  • Emerald ash borer, an invasive beetle from East Asia, has spread to Colorado, where CSU Extension estimates about 15% of urban trees are ash.[2]
  • Japanese beetles now have permanent, reproducing populations in many Front Range communities and in Mesa County on the Western Slope.[3]
  • The elm seed bug, native to Europe, was first detected in Colorado in 2017 on the Western Slope and has since spread through much of the state, including the Front Range.[4]

Pests local experts flag

  • The Rocky Mountain wood tick is the most common tick biting people and dogs in Colorado, and Colorado tick fever is by far the region's most common tick-borne disease.[5]
  • CSU Extension says brown recluse spiders are extremely rare in Colorado, and the few found usually hitchhiked in from neighboring states.[6]

Public agencies that handle pests

The Colorado Department of Public Health and Environment tracks West Nile virus, reports that Colorado has had cases every year since 2002, and says human risk is mainly from June through early September.[8]

Hiring a licensed company

Colorado's pesticide regulatory agency is the Colorado Department of Agriculture (Division of Plant Industry, Pesticide Programs).[1]

Licensing agency: Colorado Department of Agriculture — Division of Plant Industry, Pesticide Programs[1].

See also how to check a pest control license.

Free local help

CSU Extension staff and Colorado Master Gardener volunteers help residents solve insect problems, diagnose plant diseases, and identify invasive species, and lawn problems can often be diagnosed from photos or a small sample brought to a local Extension office.[9]

Local guides in Colorado

Through the year

Spring
Miller moths, the adult army cutworm, can become a serious nuisance pest in Colorado during their late-spring migration from the plains to the mountains, and severe problems are mostly limited to eastern Colorado.[7]
Spring to Summer
The Rocky Mountain wood tick is most active and bites most in spring, then goes dormant as summer heats up.[5]
Spring to Fall
Emerald ash borer adults are present in Colorado only from May to September, which makes the insect hard to detect.[2]

Sources

  1. National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)
  2. Colorado State University Extension, “Emerald Ash Borer: A Threat to Colorado’s Urban Forests.” extension.colostate.edu/resource/emerald-ash-borer-a-threat-to-colorados-urban-forests/ (accessed 2026-10-06)
  3. Colorado State University Extension, “Japanese Beetle.” extension.colostate.edu/resource/japanese-beetle/ (accessed 2026-10-06)
  4. Colorado State University Extension, “Elm Seed Bug: A Nuisance Pest in Colorado Homes.” extension.colostate.edu/resource/elm-seed-bug-a-nuisance-pest-in-colorado-homes/ (accessed 2026-10-06)
  5. Colorado State University Extension, “Colorado Ticks and Tick-Borne Diseases.” extension.colostate.edu/resource/colorado-ticks-and-tick-borne-diseases/ (accessed 2026-10-06)
  6. Colorado State University Extension, “Brown Recluse Spiders in Colorado: Recognition and Spiders of Similar Appearance.” extension.colostate.edu/resource/brown-recluse-spiders-in-colorado-recognition-and-spiders-of-similar-appearance/ (accessed 2026-10-06)
  7. Colorado State University Extension, “Miller Moths.” extension.colostate.edu/resource/miller-moths/ (accessed 2026-10-06)
  8. Colorado Department of Public Health and Environment, “West Nile virus and your health.” cdphe.colorado.gov/animal-related-diseases/west-nile-virus/west-nile-virus-and-your-health (accessed 2026-10-06)
  9. Colorado State University Extension, “Lawn, Garden & Landscape Questions.” extension.colostate.edu/lawn-garden-landscape-questions/ (accessed 2026-10-06)

Updated 2026-10-06. Every statement on this page comes from the cited state, federal or university source. Spot an error? Tell us.