The prevalence of ticks in Missouri is a significant concern for anyone spending time outdoors. The state’s climate, characterized by warm, humid summers and mild winters, creates an ideal environment for several tick species to thrive. This extended period of activity means residents and visitors must remain vigilant for a large part of the year. Understanding these seasonal cycles is key to mitigating exposure risk.
Seasonal Peaks and Dormancy Patterns
The idea that ticks simply “go away” for a season is inaccurate, as their activity is primarily governed by temperature rather than the calendar. Ticks do not die off in the cold; instead, they enter a dormant state called diapause, sheltering in the leaf litter close to the ground. Activity begins to rise when ground temperatures consistently reach approximately 40 degrees Fahrenheit.
Spring marks the major emergence, with activity spiking as temperatures moderate and humidity increases. This period from late spring through mid-summer sees the highest overall numbers of ticks questing for a host. The peak infestation period typically occurs between May and July when multiple species and life stages are active simultaneously across the state.
As the intense heat of mid-summer wanes, activity slows for some species, but the risk continues into the fall. Unfed adult ticks, particularly the blacklegged variety, remain active on warmer days, sometimes even after the first light frost. Missouri’s mild winter weather often includes periods where temperatures rise above freezing, rousing adult ticks from dormancy and creating a year-round threat.
Key Tick Species Found in Missouri
American Dog Tick
The American Dog Tick (Dermacentor variabilis) is common across the entire state and is most visible during the warmer months. Adults of this species are active from spring through early fall, with peak numbers often found from April through July in grassy fields and along trails.
Lone Star Tick
The Lone Star Tick (Amblyomma americanum) is perhaps the most aggressive feeder and is abundant throughout Missouri. Its nymphs and adults are typically active from early spring through mid-summer, while the larval stage, often called “seed ticks,” appears from late summer into early fall. The female is easily identified by the distinct white or “lone star” spot on her back.
Blacklegged Tick
The Blacklegged Tick (Ixodes scapularis), also known as the Deer Tick, follows a different seasonal pattern that makes it a threat during cooler weather. Adult Blacklegged Ticks are most active during the late fall and early spring, months when many people assume the tick risk has passed. The minute nymph stage, which is responsible for a large percentage of bites, is most active during the late spring and summer.
Essential Tick Prevention Measures
Mitigating exposure requires a multi-faceted approach that combines personal protection and habitat management throughout the extended active season.
Chemical prevention involves treating outdoor clothing and gear with products containing 0.5% permethrin, which kills ticks on contact and remains effective through several wash cycles. Permethrin should never be applied directly to the skin. For skin application, use an EPA-registered insect repellent containing active ingredients like DEET or picaridin to provide a protective barrier.
Behavioral and physical measures are also crucial:
- Wear light-colored clothing when venturing into tick-prone areas to spot crawling ticks easily.
- Tuck pant legs into socks or boots to prevent ticks from reaching the skin from ground level vegetation.
- Shower immediately upon returning indoors (within two hours) to wash away unattached ticks.
- Perform a thorough, full-body tick check, including less visible areas like the scalp and armpits.
- Reduce tick habitat in your yard by frequently mowing grass, clearing tall weeds, and removing leaf litter along wooded edges.