On June 20, 1997, at 2015 central daylight time (cdt), a Piper PA-25-235, N7378Z, operated by a commercial pilot was destroyed when it struck a power line during an aerial application pass. The airplane subsequently impacted the terrain and burned. Visual meteorological conditions prevailed at the time of the accident. The aerial application flight was being conducted under 14 CFR Part 137. No flight plan was on file. The pilot sustained serious injuries. A local farmer who witnessed the accident said that he was on his tractor bailing hay in a nearby field when at approximately 2000 cdt he saw the airplane make a low pass to the west. The airplane was approximately 1/4-mile north of his location. He saw the airplane come back around for another pass. The witness said that on the second pass the airplane dipped down in altitude a slight bit after spraying and then burst into flames. The farmer said that the sun was low in the sky at the time. A deputy sheriff for Falk County, South Dakota, who responded to the accident site said that he met the pilot of the airplane along side a dirt road. The deputy sheriff said that the pilot told him that he hit some power lines and crashed. The deputy sheriff said that the pilot was severely burned and was in a state of shock. The deputy sheriff also said that two power lines had apparently been struck. The Federal Aviation Administration (FAA) inspector who examined the wreckage at the site found the remains of the airplane resting in a field 8 miles northeast of Faulkton, South Dakota. The airplane was resting upright approximately 357 feet west of three north-south running suspended power lines, on a 270-degree heading. Two of the three power lines were severed. The power lines in the area were suspended approximately 20 feet above the ground. One of the poles supporting the power lines was hidden by trees. A ground scar was observed 198 feet west of the power lines along the 270-degree heading to the main wreckage. The airplane's fabric fuselage and empennage was severely charred so that only the metal frame remained. The airplane's left wing outboard of the immediate wing root was undamaged. The inboard section next to the fuselage was charred. The right wing's upper skin surface was charred. The airplane's main landing gear were charred and melted. The airplane's engine had broken free of the engine mounts. The propeller showed torsional bending, chordwise scratches and several deep nicks in the leading edge metal of all blades. Flight control continuity was confirmed. No anomalies were found with the engine, engine controls or other airplane systems.