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Pests and pest control in Illinois

Pests to know in Illinois

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

Pests documented in Illinois

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

Many public records (741)

Fewer public records (144)

Range named by extension sources (2)

Invasive species reported here

IDPH notes the Asian tiger mosquito, an introduced species, feeds during daylight hours rather than at night.[5]

Pests local experts flag

  • The brown recluse may be found in the southern two-thirds of Illinois and often lives in dark places such as closets and dressers.[2]
  • The northern black widow is the most common black widow in northern states such as Illinois.[3]
  • The American dog tick is the most common tick throughout Illinois.[4]
  • Blacklegged ticks are most common in northern Illinois and along river corridors.[4]

Public agencies that handle pests

IDPH's West Nile virus surveillance monitors dead crows, robins and blue jays, plus mosquitoes and horses.[6]

Hiring a licensed company

Illinois's pesticide regulatory agency is the Illinois Department of Agriculture (Bureau of Environmental Programs).[1]

Licensing agency: Illinois Department of Agriculture — Bureau of Environmental Programs[1].

See also how to check a pest control license.

Free local help

The University of Illinois Plant Clinic diagnoses plant diseases and insect pests and identifies plants, insects and other arthropods.[7]

Local guides in Illinois

Sources

  1. National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)
  2. Illinois Department of Natural Resources, “Family Sicariidae (Wild About Spiders).” dnr.illinois.gov/education/wildaboutpages/wildaboutinvertebrates/wildaboutspiders/family-sicariidae.html (accessed 2026-10-06)
  3. Illinois Department of Public Health, “Brown Recluse and Black Widow Spiders.” dph.illinois.gov/topics-services/environmental-health-protection/structural-pest-control/brown-recluse-black-widow-spiders.html (accessed 2026-10-06)
  4. Illinois Department of Public Health, “Tick Identification.” dph.illinois.gov/topics-services/environmental-health-protection/structural-pest-control/common-ticks/identification.html (accessed 2026-10-06)
  5. Illinois Department of Public Health, “Asian Tiger Mosquito.” dph.illinois.gov/topics-services/environmental-health-protection/structural-pest-control/asian-tiger-mosquito.html (accessed 2026-10-06)
  6. Illinois Department of Public Health, “West Nile Virus (WNV).” dph.illinois.gov/topics-services/diseases-and-conditions/west-nile-virus.html (accessed 2026-10-06)
  7. University of Illinois Extension, “Plant Clinic.” extension.illinois.edu/plant-clinic (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.