Pests to know in Fort Collins
Termites in Fort Collins
- At least three native subterranean termite species live in Colorado; the most widespread, the aridland subterranean termite, occurs across most of the state below about 7,500 feet.[4]
- CSU Extension says termite damage to Colorado buildings has historically been uncommon, but infestations are now more common in many residential areas.[4]
Invasive species reported here
Emerald ash borer has reached Fort Collins city limits. The City maintains about 10% of the roughly 70,000 ash trees in town; the rest are privately owned.[5]
Pests local experts flag
Fort Collins residents can request a free backyard visit from the City's mosquito contractor, who identifies breeding spots and treats possible larval sites.[1]
Climate
Central Fort Collins (ZIP 80524) is in USDA plant hardiness zone 5b, where the average coldest winter night is -15 to -10°F.[8]
Public agencies that handle pests
- Fort Collins contracts with Vector Disease Control International (VDCI), which maps mosquito breeding sites and runs light traps to track adult mosquitoes through the season.[1]
- Larimer County runs no mosquito control program of its own; many towns in the county instead work with VDCI for mosquito control.[2]
- Under city policy, Fort Collins considers spraying for adult mosquitoes only once the West Nile vector index reaches 0.75 or higher.[2]
- Larimer County health officials say plague bacteria travel on fleas carried by rodents such as prairie dogs, squirrels, rabbits and chipmunks.[3]
- In Larimer County, rabies turns up most often in skunks and bats, though foxes, raccoons and coyotes can also carry it.[3]
Hiring a licensed company
Colorado requires every commercial pesticide applicator to be licensed with the Colorado Department of Agriculture.[6]
Free local help
Larimer County Master Gardeners run a Tree Team that makes site visits, because tree problems are hard to diagnose by phone or email.[7]
Through the year
- Spring to Fall
- In Colorado, mosquito season runs from spring to mid-September, and West Nile-positive mosquitoes usually peak from mid-July through early September.[1]
Sources
- City of Fort Collins, “West Nile Virus.” www.fortcollins.gov/Services/Police-and-Public-Safety/Emergency-Preparedness/West-Nile-Virus (accessed 2026-10-06)
- Larimer County Department of Health and Environment, “Mosquito Control Information.” www.larimer.gov/health/communicable-disease/west-nile-virus/mosquito-control-information (accessed 2026-10-06)
- Larimer County Department of Health and Environment, “Animal-Borne Diseases.” www.larimer.gov/health/communicable-disease/animal-borne-diseases (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)
- City of Fort Collins Forestry, “Insects and Diseases.” www.fortcollins.gov/Services/Forestry/Insects-and-Diseases (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)
- CSU Extension in Larimer County, “Colorado Master Gardeners.” www.larimer.gov/extension/Yard-Garden/Master-Gardeners (accessed 2026-10-06)
- USDA ARS and PRISM, via phzmapi.org, “Plant hardiness zone for ZIP 80524 (2023 USDA map data).” phzmapi.org/80524.json (accessed 2026-10-06)
- National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)