Tick Season in Ontario: Where Lyme Risk Is Spreading

Why are ticks spreading across Ontario?

Blacklegged ticks are spreading to new areas in part due to climate change, and they also spread by travelling on birds and deer. One model estimated their range was moving north at 46 km a year. Young blacklegged ticks feed on mice, chipmunks and birds, and adults feed on small to large mammals such as dogs, raccoons and white-tailed deer. Researchers say migratory birds likely bring millions of ticks into Canada from the northeastern United States each year.

When is tick season in Ontario?

Ticks can be active any time the temperature is above freezing (0°C), and in 2022 adult blacklegged tick submissions in Canada peaked in May and again, slightly higher, in October. In Ontario, the blacklegged tick (Ixodes scapularis) is the only type of tick that can transmit the bacteria that cause Lyme disease. Its life cycle typically takes two years.

Watch for nymphs in summer: the City of Toronto says the nymph stage typically occurs during the summer months and is the stage most responsible for human infections. Nymphs are less than 2 mm long, about the size of a poppy seed, and the City says that very small size keeps people from noticing them on their body.

Where should you treat your yard for ticks?

A yard treatment targets the leaf litter and the edge where the lawn meets the trees, the spots where ticks spend most of their lives, rather than the whole yard. If your yard backs onto a ravine, green belt, conservation area or wooded lot, ticks are now a real health concern.

If you're finding ticks on your family or pets, or you live in a higher-risk area, have a professional look at the yard and treat it. Ontario recommends keeping grass mowed short, removing leaf litter, brush and weeds at the edge of the lawn, and creating a border of gravel or woodchips one metre or wider around your yard if you're next to a wooded area or tall grasses.