Mowing has been recommended for managing ticks where people tread, but a new study suggests that a single mow of park trails in early summer isn’t enough to reduce prevalence of blacklegged and American dog ticks. Shown here is a blacklegged tick (Ixodes scapularis). (Photo by Steve Waller via iNaturalist, CC BY-NC 4.0)

By Xia Lee, Ph.D.

Xia Lee, Ph.D.

Found throughout much of the Northeastern and Midwestern United States, the blacklegged tick (Ixodes scapularis) is responsible for transmitting the pathogen that causes more than 300,000 cases of Lyme disease and an estimated economic burden of $1.2 billion annually. Unfortunately, the small nymphal stage of the blacklegged tick responsible for causing this misery is most active during summer when people are likely to be participating in a variety of outdoor activities.

Although preventable and treatable, cases of Lyme disease in the United States have been increasing, and efforts to control the blacklegged tick are not always successful. Or, when successful in reducing tick prevalence, such efforts often do not directly correspond to a reduction in cases of Lyme disease.

One possible management strategy frequently discussed is mowing to reduce ticks in lawns and park trails. Frequent mowing will keep grass and wild vegetation to a height that makes park trails more useable for visitors and, at the same time, might make trails less suitable for blacklegged ticks. Despite their tough exoskeleton, blacklegged ticks are very susceptible to drying out, and mowing could increase tick exposure to the sun and summer heat by removing shade and moisture-conserving vegetation. Ideally, mowing would create conditions on park trails that are hazardous for blacklegged tick survival through the summer months.

However, in a new study my colleagues and I report that a single mowing in early June did not reduce the number of nymphal and adult blacklegged ticks and American dog ticks (Dermacentor variabilis) along trails at three large recreational parks. The results of this study, conducted with George-Ann Maxson at the Mississippi Headwaters Audubon Society and Susan Paskewitz, Ph.D., professor of entomology at the University of Wisconsin-Madison and director of the Midwest Center of Excellence for Vector-Borne Disease, were published in October 2022 in the Journal of Medical Entomology.

Researchers studying how a single mowing of park trails affects tick prevalence conducted their study at three nature centers in Minnesota in 2021. The image at left shows the difference in vegetation height between mown and unmown sections of trail, and the image at right illustrates the checkerboard pattern in which 200-meter sections of trail were mown on one side and left unmown on the other, with the sides alternating at each new section. (Image orginally published in Lee et all 2022, Journal of Medical Entomology

Blacklegged ticks are commonly encountered on trails within wooded habitats. In our study, we found a total of 3,001 nymphal and adult ticks (2,004 blacklegged and 997 American dog ticks). More importantly, we collected a similar number of adult ticks between the trail sections that were mown (51 percent of ticks collected) using a mower attached to an all-terrain vehicle or push lawnmower and control sections that were left unmown (49 percent). Nymphal ticks, interestingly, were more abundant on trails that were mown (56 percent) compared to the unmown controls (44 percent).

The other tick that we found in our study, the American dog tick, does not transmit the Lyme disease pathogen and is considered a biting nuisance in the Midwest. In other states, this tick can transmit the pathogen that causes Rocky Mountain spotted fever. The number of American dog ticks found along trails at the three recreational parks were also similar between the mown (47 percent) and unmown control (53 percent) trails sections for both nymphal and adult stages.

Young Naturalist Program campers hike a trail through a red pine forest at the Neilson Spearhead Center, a nature preserve owned and managed by the Mississippi Headwaters Audubon Society in Bemidji, Minnesota. (Photo by Eleva Potter)

Bemidji State University student Eric Howd marks one side of a trail at Neilson Spearhead Center as an unmown control.(Photo by Xia Lee, Ph.D.)

Although we did not assess frequent mowing (mowing once or twice a week), as recommended for control of ticks, our study assessing a single mowing in early summer showed that tick numbers, except for nymphal blacklegged ticks, did not differ before and after trails were mown, nor did tick numbers change between the mown and unmown control sections during the summer months.

The similarity of ticks between the mown and control sections were surprising, as mowing has been shown to be effective in some studies. While mowing is a necessity within parks to maintain hiking trails at a height reasonable for visitors, based on what we found from a single mowing in early summer, we cannot recommend mowing as a method for controlling blacklegged and American dog ticks.

So, those looking to enjoy the outdoors should continue to use repellents and practice other good tick preventative measures such as frequent full-body checks and wearing protective clothing.

Xia Lee, Ph.D., is a public health entomologist in the Vectorborne, Respiratory, and Invasive Diseases Unit at the Wisconsin Department of Health Services and previously a researcher in the Paskewitz Lab in the Department of Entomology at the University of Wisconsin-Madison. Email: xlee1@wisc.edu.