On September 1, 1997, at 0830 central daylight time, a Grumman-Schweizer G-164B agricultural airplane, was substantially damaged following a loss of control while maneuvering near Marksville, Louisiana. The commercial pilot, sole occupant of the airplane, was not injured. The airplane was owned and operated by the pilot. Visual meteorological conditions prevailed for the Title 14 CFR Part 137 aerial application flight for which a flight plan was not filed. The airplane departed from an airstrip near Vick, Louisiana, approximately 30 minutes prior to the accident. According to the FAA inspector who traveled to the accident site, the pilot was in the process of executing a turn to reverse direction upon completion of an aerial application pass, when the airplane stalled. Subsequent to the loss of control, the airplane impacted the ground in a left wing low and nose down attitude and came to rest in an open pasture. Examination of the wreckage by the FAA inspector revealed that both top wings and the main landing gear assembly incurred sustained structural damage. In the enclosed pilot/operator report, the pilot acknowledged that there was no mechanical malfunction prior to the loss of control. In the same document the pilot reported that in the 90 days preceding the accident, he had accumulated 500 hours of flight time. In a telephonic interview conducted by the investigator in charge, the pilot stated that the accident occurred during the first flight of the day. He added that in the morning of the accident "he felt refreshed and alert following a good night's sleep." He further stated that "his work days for the previous 4 to 5 months had been long, normally working long days from sunrise to sunset" spraying the rice and cotton crops, as well as the boll weevil infestation. The pilot further stated that "the fact that he was trying to do too much probably caught up with him" since he had gone from one contract to the other without rest.