On August 2, 1999, about 1230 eastern daylight time, an Air Tractor AT-401, N15585, registered to and operated by Thomas R. Summersill, Inc., crashed during takeoff while on a Title 14 CFR Part 137 aerial application flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft received substantial damage and the commercial-rated pilot was not injured. The flight was originating at the time of the accident. The pilot stated that he had flown several other flights that morning. The temperature was rising and he had been lowering the chemical loads from the maximum of 2,500 pounds, due to the rising temperature. At 1230, with the temperature at the landing strip at 103 degrees F, he attempted takeoff. About 3/4 of the way down the runway, the aircraft was not accelerating and he attempted to dump the chemical load to reduce weight. The aircraft lifted off the runway and collided with 15-to 20-foot brush, traveled further, and settled into a second area of brush, where it came to rest. He stated he did not have any mechanical difficulties with the aircraft.