From left, Jimmy Walker, Justin Thomas and Rickie Fowler at Erin Hills, which features thick fescue grass, a hospitable spot for bugs like ticks.

U.S. Open Grass Is an Obstacle and a Potential Health Hazard

Erin Hills’s thick fescue presents a challenge to players, but is also a hospitable spot for ticks, prompting concern about Lyme disease.

nytimes.com