On August 25, 2008, at 1145 central daylight time, an Air tractor AT-301A, N3654T, operated by R & R Spraying, Inc., collided with terrain and a fence during a forced landing in Jasper, Minnesota. The commercial pilot was not injured. The airplane received substantial damage to both wings and the empennage. The aerial application flight was operating under Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from a private airstrip near Jasper, Minnesota, shortly before the accident. The pilot reported he was spraying a field at an altitude of 5 to 10 feet above the ground, when the engine ran rough, stopped, started, then stopped again. He reported he tried to land in an open pasture, but the airplane lost too much altitude while making a left turn. The pilot leveled the wings and the airplane contacted the terrain. The airplane traveled through a fence and a ditch prior to crossing a road and coming to rest in another ditch. Post accident inspection of the airplane revealed the fuel primer control knob was not locked and it had backed out.