Fixit: Ticks' life cycle shows why they appear in spring, not summer

Q Starting in May, wood ticks appear to run wild, then they seem to disappear by July. What happens to them? I realize I am never safe from wood ticks until frost, but when is it safer to stroll through wood tick territory? Do all ticks (dog and deer) have this same cycle?

A The life cycle of the wood tick (also called American dog tick) helps explain why you see them in the spring, but not in the summer. These ticks have a two-year life cycle. Eggs are laid in early summer and hatch into larvae. They don't feed until they turn into nymphs the following spring. These immature stages are rarely noticed. After feeding a second time, the nymphs develop into adults during late summer of the second year. The adults do not feed until the following spring, when the weather turns warm, usually in April. They die after laying eggs, typically in June, thus completing the life cycle. In Minnesota, they do not transmit disease.

Black-legged ticks (formerly called deer ticks), however, are a problem from spring through fall, and they are the ones that spread Lyme and other diseases. They have a life cycle similar to the wood tick's, taking two years to finish their development. Both adults and nymphal black-legged ticks will take a blood meal from people.

When you are in known tick areas, always wear protective clothes, such as long pants and long-sleeved shirts. Whenever possible, use repellent (such as DEET), and check yourself for ticks when you return. Black-legged ticks need to be actually biting and then need to be attached for 24 to 72 hours before they can transmit any disease. If you pull a black-legged tick off of you shortly after spending a few hours outdoors, it is very unlikely it has given you any disease. However, if you experience suspicious symptoms, see your physician as soon as possible.

Jeff Hahn, professor and assistant extension entomologist, University of Minnesota Extension