On August 16, 1998, at 1615 Central Daylight Time, a Schweizer, G164B, N7502A, collided with trees, when altitude could not be maintained due to loss of engine power, near Newton, Mississippi. The aerial application flight was operated by Payne Flying Service under the provisions of Title 14 CFR Part 137, no flight plan was filed. Visual meteorological conditions prevailed at the time of the accident. The commercial pilot was not injured. The airplane was substantially damaged. The flight departed Newton Mississippi, at 1613. According to the pilot, he had been conducting agricultural operations and had dispensed approximately 13 loads of agricultural products. He was preparing for takeoff when he noticed that the engine was slow to spool up, but the run-up was otherwise normal with the engine operating at 100%. During climb-out the pilot noticed that he did not have enough power to maintain the climb, he pushed the throttle full forward, and dumped his load. Despite the pilot's efforts to regain full power, engine power continued to decrease, and he could not arrest the descent. The pilot selected an area for a forced landing. The airplane collided with trees during the attempted forced landing. Examination of the engine assembly disclosed that the first stage compressor wheel displayed evidence of erosion. There was also fresh dirt and debris on the first stage compressor assembly. Several stator vanes exhibited pre-impact bending associated with erosion (see attached engine examination report). Further examination of the engine assembly disclosed that the fuel control unit rear support bracket bolt was not installed on the fuel control unit. The post-accident examination disclosed that the fuel control unit was displaced approximately 1/4 inch from the normally installed position. Examination of the fuel control unit showed chaffing on the pump flange. According to operator's maintenance records, the engine was last inspected 128 hours before the accident. The engine had accumulated 6000 hours of operation since the last overhaul.