The pilot reported that he had made five spray runs and was completing a procedure turn when the aircraft began to sink. He immediately applied full throttle and maximum RPM but the aircraft did not respond. The pilot stated that while his attention was on avoiding some tall trees, he was unable to grab the dump cable handle. The aircraft impacted the ground, nosed over, and came to rest inverted. The cockpit was immediately engulfed in flames, but the pilot was able to free himself and escape through the left side hatch. The aircraft exploded shortly after the pilot had vacated. The engine was torn out by impact and was thrown clear of the fire. The engine was later test run satisfactorily and was considered to be capable of developing full power.