Woodchips might sound like an unlikely defence against Lyme disease, but a two-year study in Ottawa's Greenbelt has revealed them to be precisely that—a simple, cost-effective barrier that can reduce tick populations by up to 99 percent along recreational trails.
The research, led by Katarina Ost, a doctoral candidate at the University of Ottawa's School of Epidemiology and Public Health under the supervision of Dr. Manisha A. Kulkarni, tested a straightforward intervention: laying woodchip borders along trail edges where hikers are most likely to brush against ticks. The team, collaborating with researchers from Bruyere Health Research Institute, Université de Montréal, and Dalhousie University, compared untreated woodchips with those treated with deltamethrin, an insecticide commonly used in agriculture to protect crops from ticks and mites.
The results were striking. Woodchips treated with deltamethrin reduced the density of blacklegged ticks—the primary vectors of Lyme disease in eastern North America—by 99 percent across two seasons. Even untreated woodchips proved remarkably effective, cutting tick populations in half with a 48 percent reduction. Neither intervention lost its potency over time, meaning a single application maintained its protective power throughout the tick season.
This matters urgently. Lyme disease cases in Canada have surged dramatically, with reported incidents increasing sevenfold over the past decade. Ottawa itself has seen cases spike eightfold in that same period, reflecting a troubling expansion of tick habitat across central and eastern North America. Climate change, shifting land use patterns, and growing wildlife populations have allowed ticks to colonize new territory, with the highest infection rates now appearing in Nova Scotia and across southern Manitoba, Ontario, and Quebec.
By partnering with the National Capital Commission's biology team, Kulkarni's group was able to conduct their experiments on actual recreational trails within Ottawa's Greenbelt—a landscape with high densities of infected ticks and real foot traffic. The team specifically targeted blacklegged tick nymphs and adults, the most dangerous life stages for spreading disease to humans.
What makes this approach particularly promising is its simplicity and scalability. Ash tree woodchips are natural, biodegradable, and low-impact compared to conventional chemical control strategies. They can be sourced locally from existing tree maintenance or removal programs, transforming waste into public health infrastructure. As Ost noted, this tool is "practical for popular trails where environmental conditions are appropriate for targeted treatment."
The researchers have also flagged important caveats. Environmental factors—particularly proximity to bodies of water—may restrict where insecticide-treated woodchips can be safely applied, and further research is needed to understand any effects on surrounding soil organisms and non-target wildlife. The long-term durability of the intervention beyond two years also remains to be studied.
Yet for communities wrestling with Lyme disease and limited resources, woodchip barriers represent a tangible win. They are affordable, effective, and deployable now. As tick-borne illness spreads northward and eastward across Canada, simple environmental solutions like these could become essential tools in keeping outdoor recreation safe. The study was published in Ticks and Tick-borne Diseases in 2026.