THE PILOT STATED THAT WHILE ON APPROACH A ULTRALIGHT AIRCRAFT WAS PERFORMING A PARALLEL APPROACH. HE MANEUVERED TO THE LEFT TO AVOID HIM. AS HE PASSED THE RUNWAY THRESHOLD HE LOWERED THE LEFT WING TO MOVE FURTHER TO THE LEFT AWAY FROM THE ULTRALIGHT. THE LEFT WING CONTACTED THE GROUND. THE AIRCRAFT ROLLED TO THE RIGHT AND THE RIGHT WING CONTACTED THE GROUND. THE AIRCRAFT THEN ROLLED BACK TO THE LEFT, THE LEFT WING AGAIN CONTACTED THE GROUND, AND THE AIRCRAFT VEERED TO THE LEFT AND COLLIDED WITH TREES.