If you live in an area where ticks are common, part of your usual yard care routine might involve measures to reduce the number of ticks on your property. Public health organizations including the Centers for Disease Control and Prevention advise mowing regularly, clearing leaves and brush, creating a dry mulch barrier between your yard and any forest edge, and other tactics to make your yard an unfriendly environment for ticks.
Yet these anti-tick strategies may have an unintended consequence, according to recent research from the Cary Institute, an independent environmental research organization. An analysis of 94 studies published in the American Journal of Epidemiology found that these measures, which also include trimming branches, were associated with an increased risk of contracting a tick-borne illness.
Sound counterintuitive? Ilya Fischhoff, Ph.D., a disease ecologist and postdoctoral associate at the Cary Institute and lead author of the analysis, says human behavior might help explain the result. “I think it’s because doing these things exposes people to ticks,” he says. Getting rid of tick habitats means putting yourself in the path of ticks hiding there.
Here, we delve deeper into what puts you at risk for tick bites and what you need to know about controlling ticks in your yard safely.
Research Reveals Tick Risks
Researchers evaluated existing studies to find out which risk factors correlated with the risk of getting bitten by a blacklegged tick (deer tick) or getting a disease spread by one, such as Lyme disease.
They found a number of unsurprising factors that were linked with increased risk, such as the presence of deer—a common host that adult blacklegged ticks feed on and use as a mating ground—as well as land use that results in properties sharing edges with forested areas.
But anti-tick yard modification, which the researchers defined as clearing brush, trimming branches, and having a dry yard edge barrier, was also correlated with a higher risk of tick-borne disease.
Although that may seem strange at first because these strategies are recommended specifically to reduce tick populations in yards, it’s actually not that surprising, says Neeta Connally, Ph.D., director of the Tickborne Disease Prevention Laboratory at Western Connecticut State University, who wasn’t involved in the study.
“A lot of recommendation measures are based on what we know about tick biology,” Connally says. Blacklegged ticks like humid conditions rather than hot sun and dry surfaces, for example. So eliminating those tick-friendly areas should theoretically reduce the chance of encountering one of these pests.
For a long time, Connally says, research that tested those yard-related recommendations focused on finding out whether they did indeed reduce the number of ticks in an area. What researchers didn’t do, she says, is look at whether such measures meant people were less likely to get bitten by a tick or to contract a tick-borne illness.
Now researchers are attempting to answer that very question.
The problem with anti-tick yard modifications, Connally says, is that in order to get the work done, people have to put themselves in the risky edge areas and brushy habitats that ticks love. “So it’s not terribly surprising that the act of actually modifying your landscape might put you at risk for encountering a tick,” she says.
Limits of the Research
Because this analysis only looked at existing studies, there may be other important risk factors that weren’t revealed due to a lack of research.
Another important caveat is that the analysis detected only correlations; it couldn’t reveal causation. So explanations of why certain risk factors affected the risk of tick bites or disease are merely hypotheses.
Still, Fischhoff thinks the explanation for why anti-tick yard modifications would lead to a greater risk of disease is highly plausible. “You would need more data to test the hypothesis that it’s because doing this landscaping exposes people to ticks,” he says. “But that seems like a pretty reasonable hypothesis.”
Note, too, that this research only evaluated risk related to blacklegged ticks and Western blacklegged ticks. The results may have been different if the researchers had focused on other species of ticks that are more common in certain areas of the U.S.
Should You Stop Modifying Your Yard Against Ticks?
The answer isn’t clear. CR has previously written about advice from the CDC and other experts about how to modify your yard to protect against ticks.
Now, Fischhoff says that he’d hesitate to use the methods evaluated in this study—clearing brush, trimming branches, and creating a dry edge barrier—without more evidence. But he’d like to see more research about the effect of various anti-tick yard modifications, especially looking at each strategy to find out what kind of effect it has.
Connally agrees that more study is needed. “What I take away from this paper is that we really don’t fully understand the specific ways that people use their backyards that lead them to encounter ticks,” she says.
Until more research is conducted, Connally says that instead of forgetting about yard modification, people should interpret this study as a reminder to take personal protection against ticks seriously, not only when out in the woods but also when spending time in the backyard.
“When spending time outside in the yard, people should be thinking about personal protective measures,” Connally says. “Particularly when the activities in the yard include some sort of yardwork, whether it’s clearing brush or mowing the lawn or working in the garden.”
One piece of good news from the new analysis: Fischhoff’s team found that taking personal protective measures, including using insect repellent and permethrin-treated clothing, wearing long sleeves and pants and light colored clothing, bathing or showering shortly after being outside, and doing tick checks were linked to a reduced risk of tick-borne disease. The effects were especially strong for bathing or showering and tick checks.
So if you live in an area where ticks are common, when you head out to do yardwork, whether you’re planning to make anti-tick changes or simply doing routine maintenance, be sure to arm yourself against ticks. Use an EPA-registered insect repellent (see a few top-rated picks from CR below) and consider dressing in permethrin-treated clothing. When you’re finished, take a shower, do a thorough tick check, and remove any ticks that have attached themselves to you.