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Pests and pest control in La Crosse, WI

Pests to know in La Crosse

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

Termites in La Crosse

  • Winged termites in Wisconsin are small, about a quarter inch, while carpenter ants can top half an inch; termite wings are slender with very few veins.[6]
  • UW-Madison's insect lab describes termites as quite rare in Wisconsin, known only from isolated pockets, though professional control is usually needed once found.[7]

Invasive species reported here

Emerald ash borer was confirmed in the City of La Crosse in 2012, and the city's plan calls for removing and replacing all untreated ash on public property.[10]

Pests local experts flag

  • County health staff note that mice fit through a nickel-sized hole and rats through a half-dollar-sized one, and they recommend traps over poisons.[2]
  • La Crosse encephalitis takes its name from the city: the first case was a Minnesota resident diagnosed in La Crosse in 1960. In Wisconsin it spreads through the eastern tree hole mosquito.[5]

Climate

Central La Crosse (ZIP 54601) is in USDA plant hardiness zone 5a, where the average coldest winter night is -20 to -15°F.[11]

Public agencies that handle pests

  • La Crosse County's health department tracks Culex mosquitoes, the species that spreads West Nile virus, by trapping adults and testing some for the virus.[1]
  • When trapping finds high numbers of West Nile-capable mosquitoes, the county treats water on public lands to cut mosquito numbers.[1]
  • La Crosse County investigates bed bug reports in hotels, motels, apartments, and rentals; renters should go to their landlord first, then the health department if nothing is done.[3]

Local rules and responsibilities

The La Crosse County Health Department investigates rat infestation reports and can order property owners to fix conditions that feed rat and mouse problems.[2]

Hiring a licensed company

Pesticide applicators can book in-person state certification exams through Extension La Crosse County; the open-book exam has about 70 multiple-choice questions and a two-hour limit.[9]

Licensing agency: Wisconsin Department of Agriculture, Trade and Consumer Protection — Bureau of Agrichemical Management[12].

See also how to check a pest control license.

Free local help

Extension La Crosse County staff help residents with insect and disease diagnosis and plant and insect identification, backed by the UW Insect Diagnostic Lab.[8]

Through the year

Spring to Fall
La Crosse County health officials say ticks are most active in spring, summer, and early fall, and the county tracks tick-borne illnesses locally.[4]
Spring to Fall
Wisconsin mosquitoes are usually active from May to October, but La Crosse encephalitis risk peaks July through September; the tree hole mosquito bites aggressively by day near woods.[5]

Sources

  1. La Crosse County Health Department, “Mosquitoes.” lacrossecounty.org/health/environmental-health/pests/mosquitos (accessed 2026-10-06)
  2. La Crosse County Health Department, “Rats and Mice.” lacrossecounty.org/health/environmental-health/pests/rats-and-mice (accessed 2026-10-06)
  3. La Crosse County Health Department, “Bed Bugs.” www.lacrossecounty.org/health/environmental-health/pests/bed-bugs (accessed 2026-10-06)
  4. La Crosse County Health Department, “Ticks.” lacrossecounty.org/health/environmental-health/pests/ticks (accessed 2026-10-06)
  5. Wisconsin Department of Health Services, “About La Crosse Encephalitis.” www.dhs.wisconsin.gov/mosquito/lac-about.htm (accessed 2026-10-06)
  6. UW-Madison Insect Diagnostic Lab, “Termite vs Ant.” insectid.wisc.edu/2014/05/16/termite-vs-ant/ (accessed 2026-10-06)
  7. UW-Madison Insect Diagnostic Lab, “Termite Worker.” insectid.wisc.edu/2014/05/20/termite-worker/ (accessed 2026-10-06)
  8. UW-Madison Extension La Crosse County, “Horticulture.” lacrosse.extension.wisc.edu/horticulture/ (accessed 2026-10-06)
  9. UW-Madison Extension La Crosse County, “Pesticide Applicator Training.” lacrosse.extension.wisc.edu/pesticide-applicator-training/ (accessed 2026-10-06)
  10. City of La Crosse, “Forestry.” www.cityoflacrosse.org/your-government/departments/parks-recreation-forestry/forestry (accessed 2026-10-06)
  11. USDA ARS and PRISM, via phzmapi.org, “Plant hardiness zone for ZIP 54601 (2023 USDA map data).” phzmapi.org/54601.json (accessed 2026-10-06)
  12. National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)

Updated 2026-10-15. Every statement on this page comes from the cited local, state or university source. Spot an error? Tell us.