On July 20, 1997, approximately 0900 mountain daylight time, a Grumman G-164A "AgCat," N6550, registered to and being flown by a commercial pilot, was destroyed during a collision with high tension power lines and subsequent ground impact while executing a pull-up maneuver near Pingree, Idaho. The pilot was fatally injured. A post mortem and toxicological evaluation was not completed as the body of the pilot was released to the family shortly after the accident. Visual meteorological conditions existed and no flight plan had been filed. The flight, which was engaged in aerial application, was to have been operated under 14CFR137, and originated from a private airstrip belonging to the pilot/owner near Pingree. On site examination by an FAA inspector as well as Blackfoot County Sheriff personnel revealed that the aircraft impacted gently rolling terrain slightly east of a set of 161,000 volt unmarked power lines oriented along an approximate 320/140 degree true bearing line. The impact was with two of the three lower (mid tower) braided cables which measured about two inches in diameter. The two top ground wires were undamaged (refer to CHART I). According to FAA personnel there were no eyewitnesses to the accident. Additionally, they reported that the aircraft was engaged in a pull-up at the conclusion of a swath run at the time of the wire strike. The aircraft was observed at the accident site in an upright attitude. The engine was observed to have been pushed upward. Slightly short of the aircraft's engine, a large dirt impact area was noted. The engine was observed to have a substantial amount of dirt impacted around its lower cylinders. Two smaller ground impact craters were noted slightly short of the main crater, and were separated laterally by approximately the same distance as the aircraft's wheels. Also, the aircraft's lower right wing outboard leading edge displayed a number or sharp cuts characteristic of wire impacts (refer to photograph 1). Further inspection revealed gradual aft bending deformation at the outboard lower right wing leading edge (refer to photograph 2). Buckling and bending deformation of the aircraft's outboard left elevator were noted (refer to photograph 3). A substantial length of power cable was found entangled around the front right side of the aircraft where it came to rest (refer to photograph 4).