Wisconsin pest season calendar

Wisconsin's cold winters push several pests indoors for shelter, while spring and summer bring the outdoor season. These windows are keyed to University of Wisconsin-Madison Extension research, not a marketing calendar.

• Boxelder bugs

  Peak window: fall through early spring

  Boxelder bugs gather on warm walls in fall, then move indoors to overwinter. Seal cracks around windows and doors in fall, and vacuum rather than crush any that appear inside.

  Source: UW-Madison Extension (Wisconsin Horticulture)

• Cluster flies

  Peak window: fall through early spring

  Cluster flies enter buildings in fall through cracks and holes to overwinter in attics and wall voids. Seal those entry points, and vacuum or sweep up the sluggish flies that emerge on warm days.

  Source: UW-Madison Extension (Learning Store)

• Ticks

  Peak window: spring peak

  Spring is peak tick activity in the Midwest. Avoid weedy trail-edge vegetation, wear long sleeves, use EPA-registered repellents, and do daily tick checks after time outdoors.

  Source: UW-Madison Extension (Wisconsin Horticulture)

• Mosquitoes

  Peak window: spring through summer

  Mosquitoes are a regular nuisance during Wisconsin's outdoor spring and summer months. Dump standing water weekly; larvae can develop in as little as one inch of water.

  Source: UW-Madison Extension (Wisconsin Horticulture)

Windows are general guidance from the cited university extension and state sources, checked on August 13, 2026. Local weather and microclimate shift them, so treat these as planning ranges rather than exact dates.