On June 12, 2014, about 1200 central daylight time, the pilot of an Air Tractor AT 301, N8593S, made a forced landing in a field near Pearsall, Texas, following a loss of engine power. The pilot, the sole occupant on board, was not injured. The airplane was substantially damaged. The airplane was registered to Matt Fitch and operated Smith Flying Service, doing business as Fitch Flying Service, of Pearsall, Texas, under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from Pearsall about 1140.According to the pilot, he returned to the airport after spraying a corn field and noticed the cylinder head temperature was high. After landing the engine cylinders were checked for discrepancies; none were found, so he decided to continue spraying. He took off and returned to the corn field. As he pulled up from a spray run, the engine started to vibrate and lose power. He made a forced landing in a nearby field. Examination of the airplane revealed both wings had sustained substantial damage during the forced landing. According to the operator, the engine had accrued about 11 hours since the engine received extensive maintenance, including the replacement of a crankshaft. The engine was shipped to Tulsa Engines in Tulsa, Oklahoma, where, on September 3, it was partially disassembled and examined under the auspices of a Federal Aviation Administration inspector. According to the FAA inspector's report, there was a large amount of metal in the oil drain. It was noted that the number 2 cylinder front spark plug was loose. After removing all the spark plugs, an attempt was made to rotate the engine. It was seized. Numbers 4, 5, 6, and 7 cylinders had oil; number 4 cylinder had more oil. After some difficulty in removing the no. 1 cylinder, it was discovered that the piston rod had broken at the link pin. No other rods were broken. The link pin was scored and there was evidence of oil starvation of the rod bearing.