Due to climate change, ticks have begun expanding where they live by 35 to 55 kilometres each year. Subsequently, this has led to a grave increase in the number of Canadians bitten by ticks.
A tick bite can cause Lyme disease if the tick carries Borrelia burgdorferi bacteria. Lyme disease is a physically debilitating disease to humans and even dogs if left untreated.
Within Canada, two types of ticks carry the Lyme disease bacteria: deer ticks that are found in central and eastern Canada, and western black-legged ticks that are found in British Columbia.
What’s being done to control them?
Because of the growing number of ticks found in Canada, synthetic pesticides have become popular as a tick management method. Although synthetic pesticides have been decreasing the number of ticks found across Canada, they are also causing damage to the environment as well as causing health concerns to humans.
For example, in some regions where synthetic pesticides are used, essential insects such as pollinators are also being killed alongside ticks. Because of this, natural acaricides — which are natural substances used to kill ticks — are beginning to gain traction as a tick control method. However, more research is required.
Where does the research stand?
A recent study published in Scientific Reports, led by Dr. Shelley Adamo from the Department of Psychology and Neuroscience at Dalhousie University, investigated the ability of a natural acaricide to kill ticks. The natural acaricide used in this study was balsam fir needles from conifer trees, because based on previous anecdotal observations made by Adamo, the main essential oil found in balsam fir needles was suggested to have tick-killing abilities.
Deer ticks (Ixodes scapularis) that carried Lyme disease were collected locally in Nova Scotia. The ticks were placed in microcosms — artificial ecosystems used to simulate natural ecosystems — under 1 cm of balsam fir needles (experimental group) or maple/oak leaves (control group) to mimic where ticks would burrow during the winter months (referred to as overwintering).
In addition, some ticks were placed in simulated winter microcosms under balsam fir needles or maple/oak leaves. This allowed the researchers to measure whether temperature had an effect on the balsam fir’s tick-killing abilities.
What was discovered?
After two weeks of overwintering, the ticks in the experimental group began to demonstrate slower reflexes. By week 3 of the experiment, 99% of the ticks in the experimental group died. In comparison, only 57% of the ticks in the control group died.
All of the ticks in the simulated winter environment died overwintering in balsam fir needles compared to only 20% of the ticks who overwintered under maple/oak leaves.
These results demonstrate that balsam fir needles can have an impact on reducing tick populations even at low exposure (i.e., 2 weeks) and that balsam fir needles are more effective at colder temperatures.
What does this all mean?
Amano and colleagues suggest that not only are balsam fir needles effective, but they are also a less expensive and more environmentally friendly way to kill ticks. Furthermore, they were able to demonstrate that balsam fir needles were more successful in killing ticks at colder temperatures (i.e., winter) compared to warmer temperatures, which would help reduce tick numbers before the “active” tick seasons (i.e., spring, summer, fall).
The next steps would be to test these results under real-world conditions, and to find a botanical insecticide that can reduce the different types of ticks found in British Columbia.
Luckily, in Canada, balsam fir trees span from Alberta to Newfoundland. If balsam fir needles continue to be effective in killing ticks in future research, this would be a promising affordable and environmentally safe method to control the tick populations in central and eastern Canada.