The Northward March: Ticks and Changing Climates in Ontario

A decade ago, blacklegged ticks carrying Lyme disease were largely confined to specific pockets of southern Ontario — the Long Point peninsula, parts of Prince Edward County, and a few other established hot spots. Today, they've been confirmed across most of the province, including suburban GTA properties that would have been considered low-risk just a few years earlier.

The reason is simple: ticks need hosts, and host populations — particularly white-tailed deer and white-footed mice — have expanded significantly as temperatures moderate and habitat shifts. Ticks are also remarkably effective travellers. A single host animal can carry dozens of ticks across kilometre distances, establishing populations in new areas quickly. Once established, tick populations are difficult to reverse without ongoing management.

Blacklegged ticks (Ixodes scapularis) are the primary concern for Lyme disease transmission in Ontario. They complete a two-year life cycle and are active in temperatures as low as 4°C — meaning spring and fall carry just as much risk as summer, if not more. The nymph stage, which peaks in late spring, is particularly dangerous because nymphs are the size of a poppy seed and are easily overlooked.

For homeowners with properties backing onto ravines, green belts, conservation areas, or wooded lots, tick management has become a genuine public health consideration. Targeted yard treatments — focusing on the leaf litter and transition zones between lawn and wooded areas — dramatically reduce tick populations. These treatments are applied to the specific microhabitats where ticks spend most of their lives, not broadcast across the entire property.

If you've been finding ticks on your family or pets, or if your property is in a higher-risk area, a professional assessment and yard treatment can make a meaningful difference. Lyme disease is preventable, and the intervention required to protect a residential property is straightforward.