On August 6, at 2005 central daylight time, a Grumman G-164A, N9041M, sustained substantial damage when it impacted the terrain near New Boston, Illinois, after a loss of engine power during cruise flight. The pilot received minor injuries. The Title 14 Code of Federal Regulations Part 137 aerial application flight departed Aledo, Illinois, at 1900 on a local flight. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed. The pilot reported that he had finished spraying his last field for the day and was heading back to the airport when he lost power and oil pressure. He reported that smoke was pouring into the cockpit. He reported that he was over a wooded area, but he managed to make a forced landing in a cornfield. The airplane impacted the terrain and skidded up on its nose. A Federal Aviation Administration airworthiness inspector examined the airplane. He reported that one of the engine cylinders had failed and a hole was visible on the side of the cylinder. Aircraft records indicated that the 600 horsepower Pratt & Whitney R-1340-AN-2 engine had accumulated 1,026 hours since the last overhaul. The engine had accumulated 157 hours since the last annual inspection conducted on January 20, 2005.