On August 28, 1997, about 1015 eastern daylight time, a Gulfstream Schweizer Aircraft Corporation G-164C, N585CK, veered right off the runway and collided with a ditch and a fence near Beaufort, North Carolina. The airplane was operated by Shannon AG Service under the provisions of Title 14 CFR Part 137 and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the aerial application flight. The commercial pilot was not injured, and the airplane was substantially damaged. The flight was originating at the time of the accident. According to the pilot, during takeoff roll on the fifth and last load of the day, he heard a loud pop behind, and the tail began shaking. He stated that he had little rudder authority and that there was a left cross wind of about five knots. The airplane then veered right, off the runway and into a corn field. The airworthiness inspector who examined the site and the airplane reported that there were rubber marks on the asphalt runway that were consistent with the tail wheel, and no evidence of main wheel tire marks. A placard in the cockpit stated that the tail wheel should be locked during takeoff on asphalt. There was continuity of the flight controls, the tail wheel lock was not broken, and the tail wheel lock hole was not deformed.