Mayor Michael Bloomberg may not know whether graffiti is art, but he knows where he'd like it: away from property.

With British street artist Banksy invading New York City for a monthlong residency, Bloomberg Wednesday took a stand against the scourge of graffiti -- even if there is artistic merit.

"Graffiti does ruin people's property. It is a sign of decay and loss of control," Bloomberg, an art admirer and patron, said at a news conference. "There are some places for art and some places for no art and you running up to someone's property or public property and defacing it is not my definition of art."

Banksy's latest NYC piece, a fiberglass Ronald McDonald, was unveiled in the South Bronx yesterday. The installation, including a live shoeshine boy, will be on view at lunchtime on sidewalks outside different McDonald's restaurants for the next week.

Banksy pieces in NYC this month include spray paintings of the Twin Towers in TriBeCa and a beaver chomping on an actual broken metal street sign pole in East New York.