Pests to know in Denver
Termites in Denver
- At least three native subterranean termite species live in Colorado; the aridland subterranean termite is found across most of the state below about 7,500 feet.[4]
- CSU Extension says termite infestations are now more common in Colorado residential areas, largely due to moisture from poorly directed landscape irrigation and downspout drainage near foundations.[4]
Invasive species reported here
Emerald ash borer was first found in Colorado in Boulder in 2013, and CSU confirmed it in Denver in 2025; ash makes up about 15% or more of Colorado's urban trees.[6]
Climate
Central Denver (ZIP 80202) is in USDA plant hardiness zone 6a, where the average coldest winter night is -10 to -5°F.[10]
Public agencies that handle pests
- Denver's mosquito program surveys larval mosquitoes at around 70 sites citywide and applies larvicide when conditions warrant.[1]
- Denver traps adult mosquitoes at five sites across the city and sends samples to the Colorado Department of Public Health and Environment to test for West Nile virus.[1]
- DDPHE inspects public properties and right-of-way spaces such as alleys for rodents; rodent control in Denver is regulated under D.R.M.C. Chapter 40, Article 40.[3]
Local rules and responsibilities
- Denver city code requires property owners to clean biological waste from their property and pet owners to pick up pet waste, since rats can live on it.[3]
- Colorado's bed bug law requires landlords to inspect within 96 hours of a tenant's notice and generally to cover inspection and treatment costs.[8]
Hiring a licensed company
The Colorado Department of Agriculture requires anyone who applies pesticides for hire to hold a commercial applicator license; supervisors and operators must pass a general exam plus category exams.[9]
Free local help
CSU's Plant Diagnostic Clinic, Colorado's state lab, offers plant and insect identification and accepts mailed or walk-in samples at the CSU Spur campus in Denver.[7]
Through the year
- Summer to Fall
- In Colorado, adult Japanese beetles emerge from the soil in mid to late June, peak in mid to late July, and can be trapped until early September.[2]
- Spring to Fall
- In Colorado, winged termite swarmers are usually produced in large numbers in spring or fall; seeing them indoors indicates an infestation.[5]
Sources
- City and County of Denver, Department of Public Health & Environment, “Mosquito Control.” www.denvergov.org/Government/Agencies-Departments-Offices/Agencies-Departments-Offices-Directory/Public-Health-Environment/Environmental-Quality/Mosquito-Control (accessed 2026-10-06)
- Colorado Department of Agriculture, “Prevention, Mitigation and Management of Japanese Beetle.” ag.colorado.gov/plants/japanese-beetle-in-colorado/prevention-mitigation-and-management-of-japanese-beetle (accessed 2026-10-06)
- City and County of Denver, Department of Public Health & Environment, “Rodents.” www.denvergov.org/Government/Agencies-Departments-Offices/Agencies-Departments-Offices-Directory/Public-Health-Environment/Public-Health-Investigations/Pest-Information-Center/Rodents (accessed 2026-10-06)
- Colorado State University Extension (PlantTalk Colorado), “1400-3 – Termites in Colorado.” planttalk.colostate.edu/topics/insects-diseases/1400-3-termites-colorado (accessed 2026-10-06)
- Colorado State University, Department of Agricultural Biology, “Termites - Agricultural Biology.” agsci.colostate.edu/agbio/ipm-pests/termites/ (accessed 2026-10-06)
- Colorado State Forest Service, “Emerald ash borer now detected in more than 20 Front Range cities.” csfs.colostate.edu/2025/10/21/emerald-ash-borer-now-detected-in-more-than-20-front-range-cities/ (accessed 2026-10-06)
- Colorado State University, Department of Agricultural Biology, “Plant Diagnostic Clinic - Agricultural Biology.” agsci.colostate.edu/plantclinic/ (accessed 2026-10-06)
- Colorado General Assembly, “HB19-1328 Landlord And Tenant Duties Regarding Bed Bugs.” leg.colorado.gov/bills/hb19-1328 (accessed 2026-10-06)
- Colorado Department of Agriculture, “Pesticide Applicator Certification and Licensing Program.” ag.colorado.gov/plants/pesticides/pesticide-applicator-certification-and-licensing-program (accessed 2026-10-06)
- USDA ARS and PRISM, via phzmapi.org, “Plant hardiness zone for ZIP 80202 (2023 USDA map data).” phzmapi.org/80202.json (accessed 2026-10-06)
- National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)