Ticks are common pests that can transmit diseases to humans and animals. Understanding the temperatures at which ticks perish is useful for public awareness. While resilient, ticks are vulnerable to extreme heat and cold.
Tick Tolerance to Cold Temperatures
Ticks endure cold conditions by entering a dormant state called diapause, conserving energy and suspending host-seeking. While they can survive brief freezing exposures, sustained periods below certain thresholds are lethal. For many tick species, particularly the black-legged (deer) tick, activity generally decreases when temperatures fall below 40°F (4°C).
This 40°F (4°C) mark is not a strict cutoff for activity; ticks may still emerge during warmer winter days, particularly if there is no snow cover. In laboratory settings, lethal temperatures for ticks typically range from -2°F to 14°F (-19°C to -10°C). To significantly impact tick populations in natural environments, temperatures often need to drop below 10°F (-12°C) and remain there for several days. Even under these harsh conditions, only about 20% of the tick population may succumb to the cold alone.
Different tick species exhibit varying cold tolerances. For instance, the black-legged tick, known for transmitting Lyme disease, can remain active at lower temperatures and survive as low as -7°F (-21.7°C) by drawing water out of its cells to prevent ice crystallization. Larval ticks generally have lower cold death points than nymphs or adults, although they are still vulnerable to sustained freezing.
Tick Vulnerability to High Temperatures
Ticks are highly susceptible to high temperatures. Specific temperature thresholds and durations are effective for eliminating them. For example, placing clothing directly into a dryer for a minimum of 6 minutes on high heat will effectively kill ticks.
This method is effective primarily due to desiccation, as ticks require moisture to survive and rapidly dry out in hot, dry conditions.
If clothing is soiled and requires washing first, studies indicate that water temperatures of 130°F (54°C) or higher are needed to kill all nymphal and adult ticks. Half of the ticks may survive hot water washes if the temperature is below 130°F (54°C), and the majority (94%) survive warm washes (80-115°F or 27-46°C). Cold water washes are not effective, with all ticks surviving in temperatures between 59-80°F (15-27°C).
If ticks survive a wash cycle, drying on a high heat setting (129-185°F or 54-85°C) can take up to 50 minutes to kill them. Sustained exposure to temperatures above 95°F (35°C) causes ticks to dehydrate rapidly, leading to their demise.
Environmental Factors Affecting Tick Survival
Factors beyond direct temperature, such as humidity and habitat, significantly influence a tick’s ability to survive temperature extremes. As ectothermic organisms, their body temperature is regulated by their environment. They require high humidity, typically above 85%, to thrive, as dry conditions can lead to rapid desiccation and death.
This explains why ticks are often found in moist environments like leaf litter and tall grass, which provide microclimates buffering them from temperature extremes. Leaf litter and snow cover act as insulators, protecting ticks from lethal ambient temperatures. For instance, while air temperatures might be frigid, the temperature within leaf litter may not drop below -5°C to -10°C, allowing ticks to survive.
The life stage of a tick also impacts its survival; larvae are particularly sensitive to desiccation and are restricted to areas with high relative humidity. Warmer temperatures, especially when combined with low humidity, can accelerate water loss in ticks, further reducing their survival rates.