-WARNING-

The Black Course Is An Extremely Difficult Course Which We Recommend Only For Highly Skilled Golfers.

Mike Asheroff can still remember that day in 1981 — or was it 1982? — when the sign was first created to prepare golfers for the challenge of playing Bethpage Black.

It’s not something Asheroff, who retired in 1994 from a long career working for Long Island and New York City Department of Parks, seeks credit for.

But with the PGA Championship headed for Bethpage Black this week, anyone wanting to know more about the famous sign needs to hear Asheroff’s story.

The sign is a tourist attraction now. Despite the 18-hole challenge that awaits each foursome, the day begins with a mandatory photo by the famous sign. It normally draws the only smiles of the day.

The “Warning” sign at Bethpage Black is so well known an image of the sign is featured on much of the apparel for sale at the PGA Championship that begins Thursday. It makes sense. The sign is Bethpage Black’s signature.

Asheroff was the deputy regional director for the Long Island State Parks when the sign was first created, and he customarily spent holidays and weekends visiting with park superintendents believing “if they were working they ought to see the boss is working,” Asheroff said.

He said the sign originated on Memorial Day, either in 1981 or ’82, maybe even 1980. Asheroff said he was sitting having coffee with Eric Siebert, who was the parks superintendent at the time, when Siebert’s two-way radio alerted them of an altercation on the golf course.

“We went out there and some guy had decided he was going to teach his wife to play golf on Memorial Day on the Black Course,” Asheroff told The Post in a telephone interview. “There were four or five empty holes in front of them and a foursome of very angry Asian golfers behind them. They were getting upset with the man and the woman and their English wasn’t good. To hurry them up, they hit several balls into him and his wife. He turned around and hit the balls back at them. They all became extremely angry.

“The park police showed up. We managed to get this guy off the golf course. His wife was mortified. We refunded his green fee and told him to go away.”

Here’s where the legend of the Black Warning Sign is born.

“I turned to Eric at that point and said, ‘Give me a piece of paper,’ and I scribbled out the wording of the sign and said, ‘Get the sign shop to make this up and put it by the park register and if anybody wants to play golf on the Black, point it out to them.’ That’s how the sign got out there,” Asheroff recalled.

Until this week, the origin of the sign had been one of the best-kept secrets in golf. A spokesman for Bethpage State Park told The Post, “There’s literally no history on that sign.”

Asheroff, now living a quiet life on Long Island, said he hadn’t thought about the sign as anything more than an answer to the problem of slow play.

“It’s a public golf course,” he said. “You can’t say to somebody that your golf skills are not good enough to play on this golf course. It’s a public course. What you’re trying to do is encourage them to understand there could be an issue, so please don’t do this. And that’s all it was. We were trying to solve a problem.”

Dave Catalano, the director of Bethpage State Park from 1995 to 2011, watched the sign grow from a local novelty into a nationally known symbol beginning with the announcement the 2002 U.S. Open would be played there. Stories about golfers sleeping in the cars overnight for a tee time endeared the public course to the nation, a sentiment duplicated when the U.S. Open returned in 2009.

“That’s when everybody started getting crazy about Bethpage,” Catalano said. “Bethpage was on everybody’s radar locally. But once the Open got announced and the public embraced it unbelievably, that sign really took off.”

With popularity come contrarians. Catalano has heard there are some who insist a similar warning sign was visible more than 50 years ago. But Catalano said he doesn’t remember seeing a sign until the early to mid-’80s and backs Asheroff’s version of its origin.

“I believe that his claim is absolutely factual,” Catalano said. “Other people claim to have remembered seeing the sign in the ’50 and ’60s and ’70s, but I have no such recollection of a sign being there. But I’m not going to stand on a stack of Bibles and say there was no sign there. I do recollect a sign being there in the early to mid-’80s.”

Asheroff doesn’t want credit for creating the sign, however.

“It never entered my head anything about this sign until someone texted me recently,” he said. “If you asked me two weeks ago about that sign, I thought it would have been taken down because it wasn’t needed anymore.

“It wasn’t something to take credit for. We were doing our jobs. My job was to serve the public. If I could serve the public better by shooing people away in a gentle manner, then that’s good. If somebody else wants credit for it, God bless them. Let them. I can’t even tell you whether the words that are on there now are the same words that I used.”

Today the sign has the opposite effect than what Asheroff intended. Instead of discouraging golfers, it encourages them to come from all over the world to stand by the sign and take a picture before embarking on their round over the now famous public course.

Asked if the sign has ever discouraged play, Catalano offered: “I will tell you categorically absolutely not. People who want to play the Black Course play the Black Course whether they shoot 175 or they shoot the course record. They want to play the course.”

Had the sign actually discouraged play, Catalano might have considered taking it down.

“We never made any attempt, nor do I believe we should have made any attempt to prevent somebody from playing the golf course,” he said. “It’s a public gem and it’s been a public gem since it opened in 1936 and God knows how many people have played it.”

Encouraged by a warning sign that creates more smiles than fear.