Mayor Bill de Blasio on Friday defended using city employees to tell park visitors not to feed the rats.

The Post reported earlier this week that Parks Department enforcement patrol officers were under orders to regularly visit 30 rat-infested parks to warn visitors that the rats are a health hazard and not to leave behind trash that attracts the rodents.

“The [city’s] anti-rat initiative has many, much bigger elements to it,” including new trash cans and using dry ice to kill them, said de Blasio at an unrelated press conference.

“So, the point you’re raising is about a very small initiative in a much bigger arsenal of weapons we’re using to go at rats.”

Members of the union that represents the roughly 300 parks officers have ripped the plan, saying it’s a waste of resources when there are so few to patrol 30,000 acres of parkland.

When told about de Blasio’s remarks, Local 983 President Joseph Puleo shot back, “It might be a small piece of his initiative, but he’s using a big chunk of our patrol hours when we should be patrolling parks and preventing crime.”