MADISON, Wis. » Wisconsin authorities announced Tuesday they will shut down one of nation’s most popular nude beaches on weekdays after struggling for years to curtail sex and drugs on the sandbar and surrounding woods.

Nudists from around the country have been traveling to the public beach on the Wisconsin River near Mazomanie, about 25 miles northwest of Madison, for decades as word spread that prosecutors in ultra-liberal Dane County wouldn’t go after anyone for showing skin. But visitors haven’t stopped at just stripping down. They’ve been slipping off into the woods for trysts and drugs.

Authorities say that’s crossing the line, but they haven’t been able to stop the shenanigans. Their frustration reached a tipping point Tuesday, when the state Department of Natural Resources announced it will close the beach, the islands immediately off it and the surrounding woods to the public on weekdays, when wardens say troublemakers tend to operate unseen. The closures begin immediately. The area will remain open on weekends, though.

Bob Morton, executive director of the Austin, Tex.-based Naturist Action Committee, which lobbies on behalf of nudists, has visited the beach several times. He criticized the DNR for not consulting with beachgoers before closing the area.

“Honestly, we’re on their side when it comes to enforcing things that are lewd and lascivious,” Morton said. “There’s something to be said about consulting the users of the place. There’s got to be more to this somewhere.”

Nate Kroeplin, who supervises DNR law enforcement in Dane County, said wardens reviewed data on citations and determined most violations happen on weekdays, when fewer people are around to police each other’s behavior. Of the 92 citations wardens issued for disorderly conduct or drugs in the beach area between 2008 and 2012, 83 were given on weekdays, he said.

“Obviously we’re disappointed when we have to shut any portion of our property down,” he said. “But our ultimate goal is to have a safe place anybody can feel comfortable using. And with the current activity going on down there, that’s just not the case.”

The beach has been a problem for wardens for years. The DNR purchased the area in 1949 in an effort to open up more land for public hunting, fishing and recreation. Droves of nudists claimed the beach as their own, though, emboldened by local prosecutors’ indifference. Wisconsin law makes exposing one’s genitals a misdemeanor, but a long line of Dane County district attorneys have said naked people must cause some kind of disturbance before they can be prosecuted. The DNR estimates as many as 70,000 people, some from as far away as Florida, have visited the beach some summers.

With all the skin has come sex and drugs. Warden arrest reports tell graphic stories of oral sex and mutual masturbation.

The agency closed the area at night and banned beach camping in the late 1990s. Authorities also installed a gate blocking vehicles in hopes of stopping people from driving down to the beach in search of quick sex.

In 2007, wardens closed off parts of the woods around the beach to discourage sex in the underbrush and cut down brush around the beach to eliminate cover. But arrests for sex and drugs around the beach still hit a five-year high in 2011; wardens arrested 26 people for sex and 16 people for drugs in just nine days of surveillance.

The DNR closed another 70 acres around the beach last spring, but Kroeplin said it hasn’t stopped people from cruising the beach parking lot on weekdays, when relatively few people are around to complain. Last summer, wardens issued 19 citations for sex and three for drugs over five or six days of surveillance, Kroeplin said; 16 citations were issued on weekdays compared with six on weekends.

“It’s pretty incredible to see the amount of traffic that pulls onto the property,” Kroeplin said. “Everything we’ve done has not made any difference.”