On August 6, 2013, at 0856 mountain daylight time, a Piper PA-36-300 airplane, N3789E, was substantially damaged after ground impact near Santa Teresa, New Mexico. The pilot did not report any injuries. The airplane was registered to Valley Ag Aerial Services and was operating under the provisions of 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed for the local flight, which departed without a flight plan from a private airfield near San Miguel, New Mexico, about 0830. The pilot stated that he arrived to spray a small cotton field, which was divided by a diagonal power line. After a spray pass on the north side of the power line, he maneuvered the airplane for a spray pass on the south side of the power line. Due to the power line and heavy construction equipment near the approach end of the pass, the pilot conducted an approach with a steeper angle. During the pull-up from this pass, the airplane struck a tree at the departure end of the field. The pilot was unable to maintain roll control and maneuvered to a forced landing, during which the airplane cartwheeled in a grass field. Both wings and the rudder were substantially damaged. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot stated that the land owner had made multiple requests to spray the small, tightly confined field and he regretted his decision to accommodate the request. He had sprayed this field during previous years and realized that it was challenging to spray due to its size and the obstacles. The pilot made a habit of sleeping at least seven hours per night. On the night prior to the accident, his sleep was interrupted about five to eight times by a dog that he was taking care of for a friend. Since the spray season started in the spring, he had consistently averaged about 6 work days a week. During the last month, he averaged about 4 hours of flight time, per day, conducting spray operations. In retrospect, the pilot stated that he was fatigued at the time of the accident.