On August 26, 1995, at 1845 central daylight time, a Grumman G- 164A, N8783H, was substantially damaged during a forced landing near Trumann, Arkansas. The commercial pilot was not injured. The aircraft was being operated on an aerial application flight by Simmons Flying Service Inc., under 14 CFR Part 137 when the accident occurred. The flight originated in Jonesboro, Arkansas, at approximately 1815 CDT. Visual meteorological conditions prevailed for the local flight for which no flight plan was filed. According to the operator, the pilot noticed that the engine was smoking heavily and losing power while spraying pea fields during an aerial application flight. The pilot stated that the degradation of engine power continued to the point where he was unable to maintain level flight, so he elected to execute a forced landing to a bean field. During the landing roll, the airplane impacted a ditch at the end of the bean field causing the airplane to nose over and come to rest in the inverted position. Post-accident examination of the airplane revealed that the airframe sustained structural damage. The reason for the loss of engine power could not be determined.