The pilot stated his duty day started at 2000 hours eastern standard time the night before the accident. He repositioned the helicopter to an airport near the bean fields in preparation for low-level agricultural sustainment flights. He drove a vehicle to several bean fields and preformed a ground reconnaissance of known hazards in preparation for flights that would be flown that evening or in the early morning hours on the following day. He flew one mission that lasted 1 hour 30 minutes before midnight, landed, and went to bed. He was awakened when another helicopter had an accident on the airport at 0030. He went back to bed at 0100, was awakened again at 0300 and departed to fly at 0330. He was flying up and down the bean field at a low altitude, from south to north, with an east to west pattern. He observed power lines at the end of the field, crossed over them and descended the helicopter into the ground at 0730. When asked if there were any mechanical problems with the helicopter, the pilot stated no. He stated he was tired. He had been awake for 18 hours and 30 minutes and had slept 2 hours prior to the accident. He further stated he had slept 5 hours 30 minutes in the last 24 hours and 14 hours in the last 72 hours.