THE PILOT WAS ATTEMPTING TO PICK UP A BANNER LOCATED ADJACENT TO GARDEN STATE PARKWAY. THE BANNER WAS SUCCESSFULLY PICKED UP, BUT THE PILOT STATED THAT IT FELT HEAVY EVEN WITH FULL POWER BEING APPLIED. HE APPLIED RIGHT RUDDER PRESSURE TO CORRECT A WING LOW ATTITUDE & FORWARD PRESSURE TO LOWER THE AIRCRAFT NOSE. THE AIRCRAFT DID NOT ACCELERATE. AS THE PILOT REACHED FOR THE BANNER RELEASE, THE LEFT WING CLIPPED A 20 FT PINE TREE & THE AIRCRAFT CARTWHEELED COUNTERCLOCKWISE, IMPACTING THE GROUND IN A NOSE DOWN ATTITUDE.