The tick-resistant yard
How to tweak your property in the Age of Lyme
By Becca Tucker
Every age comes with its dangers. We’ve managed to eliminate many. Ticks, with the growing list of dread diseases they carry, are our big one, and getting bigger.
Ticks are burrowing their way into our pant legs, dogs’ fur and our dreams. We know by now to do tick checks, to bathe after being out in the woods, to wear light colors and tuck those pant legs in, to wear repellent. But how about our yards? What can we do to keep ticks off them?
There’s no silver bullet. “It’s going to be impossible to keep ticks out of your yard because rodents come in and transport them,” said Dan Daly of Dan’s Pro Grow in Goshen, NY. The science is still emerging, frustratingly slowly – and often, the science surprises us. What we’re learning is that these systems are so complex, with so many players, that we don’t yet understand how changing one part will affect the whole. For instance, fencing deer out of a yard smaller than six acres actually increases the tick density inside the fence, according to a controversial 2006 meta-analysis, highlighting just how much we don’t understand.
Still, by now we’ve learned enough about ticks that we can start to consciously, proactively evolve. One way to do that is to tweak our yards, to minimize our chances of getting laid low by a tiny, eyeless, not particularly fast-moving parasite.
5) Let in more sun
In high traffic areas of your property – like the playground, around the house, the lawn – open up to direct sunlight, recommends the Connecticut Agricultural Experiment Station in its Tick Management Handbook. Ticks require high humidity; they dry out in bright, sunny areas. Pruning bushes and trees, and keeping your lawn mown and leaves raked, also reduces tick and small mammal habitat and cover. You can prune bushes so that there’s space between the ground and the base of the plant, says the handbook.
Within your high traffic zone you’re going for a park-like feel. “Clean up storage areas, woodpiles, and junk piles,” Cornell Cooperative Extension says. Yes, Mom.
Caveat: This is a balancing act because you don’t want to clear out all your wildlife habitat. Certain critters help in keeping ticks down, either by eating mice that host and infect young ticks, or by eating ticks themselves. Those weird, drunk-looking opossums that stumble around at night turn out to be fastidious groomers that hoover up thousands of ticks a week. Of the fraction that survive the opossum’s licking and swallowing, only 3 percent of those ticks get infected with Lyme, versus about half of ticks that feed on mice.
“What we find in general is that high animal diversity has a pretty strongly protective effect when it comes to tick-borne disease,” said Dr. Rick Ostfeld, a tick researcher at the Cary Institute of Ecosystem Studies in Millbrook, NY. “Not just Lyme, but babesiosis, anaplasmosis, and these other tick-borne infections.”
Still, the predator population in your region is probably not something you can do much about, unless you have a giant property or are very involved in local conservation efforts.
4) Rake up
Ticks like leaf litter, shady and moist, preferably with an overstory of trees or at least shrubs. Females deposit their thousands of eggs in leaf litter in spring, and the larvae emerge in the fall, crawling onto low lying vegetation.
Removing leaf litter in early spring and again in early summer reduces tick nymph density by 73 to 100 percent, according to a 1995 study in an entomology journal. Nymphs, which emerge in May and June, are the second of the three tick life stages; and they’re particularly dangerous because they are potentially infected with disease, but at the size of a freckle, still plenty small enough to escape detection.
Get right up to the edge of the yard, says Steve Ceol, of Ecotect Scientific Pest Elimination in Sussex, NJ. “That’s probably the worst possible place, right on the edge where the leaves are,” he said.
You can compost leaves somewhere out of your high traffic area, or use them as a bedding in the chicken coop.
Caveat: Several communities in Westchester have been promoting a Love ‘Em and ‘Leave ‘Em campaign, encouraging homeowners to mulch their leaves in place by running over them with a lawnmower. It is certainly a greener option than bagging leaves and sending them to a landfill. But what effect does it have on ticks? A 2015 Cornell study attempted to answer that question, examining parks and yards whose leaves had been mulched-in-place for one to seven years and comparing them to properties that had bagged and removed the leaves. But they didn’t find enough ticks to be statistically significant, concluding that the study needs to be improved and repeated. The study’s author mentioned an intriguing possibility: Since raking and bagging leaves exposes homeowners to ticks, it’s possible that mowing the leaves instead could reduce your risk of coming into contact with ticks.
3) Buffer tick hotspots
We know certain areas tend to have more ticks than others: woods, dense vegetation, groundcover, as well as woodpiles and stone walls, which harbor mice and small rodents, the biggest culprits when it comes to infecting and transporting ticks.
Woodpiles close to the house are a fact of life if you heat your house with wood. Stone walls are beautiful – and beneficial wildlife use them too, said Ostfeld, who has watched a bobcat hunt along a stone wall. Bobcats are our ally in keeping ticks down. Each decision is a trade-off.
When you start to understand where ticks hang out, you can decide when it makes sense to buffer high-traffic areas – walkways, playgrounds, picnic tables, gardens – from tick hotspots, or else do an extra-thorough tick check after hanging out there. The Connecticut tick handbook recommends enforcing your lawn’s perimeter with a three-foot-wide path of mulch or stone, and leaving a nine-foot “tick migration zone” of empty space inside the mulch. That’s because 82 percent of nymphs are found within three meters – or about nine feet – of lawn edge with woods or stone walls.
Simply pulling your playground equipment away from the woods and into a sunny part of the yard will help, too, said Ceol, of Ecotect. Kids suffer from some of the highest rates of Lyme.
Some pet owners dust their property line with diatomaceous earth, a powder made from a naturally occurring rock, which acts as a tick and flea repellent, said Dan Daly, of Dan’s Pro Grow in Goshen, NY. But you have to repeat after it rains. Others strategically place a variety of rodent repellents, from mint oil on the natural end to moth balls on the toxic end. “If we can try to minimize rodents -- a raccoon or opossum will climb in anyway, no big deal,” said Daly, of Dan’s Pro Grow. “What we try to do is just eliminate the biggest carriers.”
Caveats: The three-foot mulch barrier has become standard advice. But before you go to all that trouble, Ostfeld says: “from the smallest mouse or shrew up to deer or raccoons, a couple of meters of woodchips is nothing. It’s not a barrier at all. There is actually no evidence that a woodchip barrier keeps ticks out of your lawn.”
Rodent repellents probably only work if there’s not much reason for a rodent to cross that barrier. A motivated mouse or chipmunk will find its way in, said Ostfeld, who is also a rodent expert.
2) Keep backyard poultry:
You hear it all the time: guinea hens eat ticks. Some scientists dismiss this “Christie Brinkley-ism” -- the former model ignited the trend when she and then-husband Billie Joel kept a flock of guineas as tick patrol on their 20-acre Hamptons property in the nineties. The resulting 1992 Long Island study, which found fewer ticks where guineas had free-ranged, makes a case for keeping these loud, unfortunate looking birds.
Chickens eat ticks, too, as everyone knows. As a chicken keeper, I like seeing my feathered girls patrolling through leaf litter, pecking creepy crawlies, while my bipedal girls play nearby. But weirdly, all the science I could find in chickens’ favor is a 1991 study in a veterinary journal, which found that in Kenya, chickens that had scavenged for 30 minutes to an hour among tick-infested cattle had between 3 and 331 ticks in their gizzards, with an average of 81 per chicken.
Caveat: A subsequent study found that while guineafowl do eat adult ticks, they don’t significantly reduce the density of nymphs, which are the most dangerous – since adults are bigger and easier to see. And did we mention that guineafowl are super loud and annoying? Keep in mind that Brinkley had 20 acres. As for chickens, there is shockingly little research out there. Despite reams of anecdotal evidence that a free-ranging flock helps keep tick numbers down, no one has bothered to study it yet.
1) Search and destroy barberry.
If you’re going to make one change, it’s one that would never occur to you in a thousand years: get rid of your barberry bushes. My what? Japanese barberry is everywhere. Originally introduced to the U.S. as an ornamental, its sharp spines make it deer-resistant. Combined with its ability to root from the stems, it has spread with a vengeance, forming impenetrable thickets in disturbed woods and along lawn edges. It forms protected thickets that create a humid understory that turns out to be a breeding ground for the black-legged tick that’s most prevalent here, as well as their most dangerous hosts -- mice, which feed on the barberry’s abundant red berries. Mice, remember, are the biggest culprits when it comes to disease reservoirs. If you’ve got a barberry thicket, not only will you have more ticks, you’ll have lots more ticks with nasty diseases like Lyme and babesiosis, a 2017 study showed.
The decade-long study by the Connecticut Agricultural Experiment Station found that a forested acre with barberry stands has 120 Lyme-infected ticks, while a barberry-free acre of forest has just 10. Does that make you itch?
It’s not easy to kill barberry. “I would just suggest digging them out or cutting them back several times through course of year, eventually killing the plant,” said Daly. At our house, we tie up our goats next to barberry plants and let them go to town, and at our neighbors’ houses, too.
The tricky part is that it’s the barberry thickets, more than the individual plants, that create tick breeding hot spots, and those stands take root in the woods, or in overgrown areas between yards. “Sure, removing barberry would help reduce tick habitat in your yard,” said Dr. Scott Williams, a researcher in the forestry department of the Connecticut Agricultural Experiment Station. Williams is the scientist who originally noticed that after being out in the Connecticut woods trying to control invasive barberry, he and his crew found lots of ticks on themselves -- and then spent a decade studying his hunch. But the real culprit is “the large infestations in your back woods that shade out sunlight and keep a humid microclimate throughout the day for ticks to thrive and seek hosts.”
While you’ve got the weed whacking equipment out, there’s another invasive species, honeysuckle, you’ll want to clear. Honeysuckle forms thickets that are 18 times denser than the native vegetation around it, and a 2010 study found that these stands harbor the lone star tick. Identifiable by the white spot on its abdomen, the lone star tick is increasingly coming up from the south, bringing with it a new suite of diseases, like this strange one: a bite from an infected lone star tick can leave you allergic to meat.
Caveat: Simply cutting barberry may not be enough to kill it, warns the Connecticut Agricultural Experiment Station. They recommend using some combination of cutting, herbicides (which we’re not into), directed flame – think propane torch or flame weeder – or, if you’re a pro, careful controlled burning. You’ve got to get back out there every five years at minimum, say the study’s authors, to keep barberry from bouncing back.