Vandals have destroyed several of Wollondilly Pony Club’s cross country jumps.
The club also found glass smashed across the course two weeks ago.
Events secretary Karen Swan has asked locals to be on the look out for anyone looking or acting suspiciously on the club’s private grounds.
“Can people who travel along Thirlmere Way past the club please keep an eye out for trespassers on our grounds and phone the police if you see any suspicious,” she said.
“For example, teenagers around 12 to 15 years old on BMX bikes.
“Destroying property is an offence and stealing is a crime.
“Let alone the fact that it is shameful and disgusting that these kids have destroyed years of our hard work.”
Last month the vice president found a hut built at the back of the club’s grounds near the cross country course.
“She found an empty bottle of scotch and beer bottles stashed down the back of the grounds,” Ms Swan said.
On Sunday May 7, children from the club found the jumps destroyed as well as timber, road signs and beer bottles scattered.
“We noticed the jumps had been chopped up and it appears that teenagers are building a bike ramp across the creek,” Ms Swan said.
“Members of our club saw teenagers climbing through the fence from a housing development site but we have never seen anyone actually destroying the jumps.”
Ms Swan is asking parents to talk to their children and warn them about going onto private property.
“Some parents might think their child is going to the skate park, which the kids might think is boring so the go wandering,” she said.
“It is dangerous for the kids to be down on the grounds in the middle of nowhere.
“They could fall or injury themselves when they are jumping across the creek.
“It is also dangerous for the horses if they pick up glass.”
Ms Swan said if further destruction happened then the club would report it to the police and consider putting up ‘private property’ signage to try and deter trespassers.
Ms Swan said club members cleared the grounds of bushland about 40 years ago and the club had since grown, extended and maintained the grounds.
The clubs are used for the first and third weekends of the months and Riding for the Disabled also use the grounds.