Chiggers are tiny, almost invisible pests whose bites cause irritating welts. Understanding their environmental tolerances, particularly temperature, is important for managing them.
Understanding Chiggers and Their Preferred Environment
Chiggers, also known as red bugs or harvest mites, are a type of mite, not an insect. Only the larval stage of the chigger feeds on humans and animals. These larvae are microscopic, measuring less than 1/50th of an inch. They typically attach to a host for several hours, injecting a digestive enzyme that liquefies skin cells, which they then consume.
Chiggers thrive in environments that offer moderate temperatures and high humidity. Their ideal ground temperature range is between 77°F and 86°F. They are commonly found in tall grasses, overgrown fields, wooded areas, and near natural bodies of water. These locations provide the dense vegetation and moisture they prefer.
When Cold Kills: Chiggers and Freezing Temperatures
Cold temperatures significantly impact chigger activity and survival. Chiggers become inactive when temperatures drop below 60°F. Chigger larvae, the biting stage, die when temperatures fall below 42°F. Other life stages, such as eggs and nymphs, also do not survive winter conditions, dying when temperatures fall below 47°F.
Adult chiggers, however, can survive winter by burrowing deeper into the soil. They can enter a dormant state, or diapause, allowing them to endure periods of cold. While adults can overwinter, the subsequent population size in the spring is influenced by the severity of the cold. A very cold spring can limit their growth, potentially reducing the population for that year.
When Heat Kills: Chiggers and High Temperatures
High temperatures can also be lethal to chiggers, particularly when combined with dry conditions. Chiggers do not tolerate temperatures above 100°F. They actively avoid objects hotter than 99°F, which is why sun-baked rocks are chigger-free. Prolonged exposure to direct sunlight and dry conditions can lead to their demise through desiccation.
While chiggers are most active on warm, humid days, low humidity can limit their activity even when temperatures are high. Hot, dry weather can cause pest populations to die off. However, dense vegetation can provide shade and maintain a moist microclimate near the soil, allowing chiggers to persist even during hot, dry spells.
Leveraging Temperature for Chigger Control
Understanding chigger temperature tolerances is useful for preventing and controlling infestations. After spending time outdoors in chigger habitats, promptly washing clothes in hot water is effective. Using a clothes dryer on high heat after washing further helps to kill any remaining chiggers. This ensures any mites that hitched a ride on clothing are eliminated before they can cause bites.
Environmental management also benefits from temperature awareness. Keeping grass cut short and vegetation well-trimmed can raise soil temperatures and lower humidity, making outdoor areas less hospitable to chiggers. While adults can survive winter, a hard freeze will kill off chigger larvae and nymphs, impacting future populations. Scheduling outdoor activities to avoid peak chigger activity, which occurs in warm, humid conditions, can also help reduce exposure.