On August 2, 2003, about 0740 central daylight time, a Rockwell International S-2R, N4923X, was destroyed following an in-flight collision with power lines during an aerial application flight near Mitchell, South Dakota. The airplane subsequently impacted a tree and terrain and burned in a post-impact ground fire. The pilot reported minor injuries. The aerial application flight was being operated under the provisions of 14 CFR Part 137 without a flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight originated from MJ Aviation Airport I, near Letcher, South Dakota, at 0700. The pilot reported that he circled the field to look for obstacles and then started spraying. He said that his airplane's main landing gear caught the wires that ran through the middle of the field. He stated: I proceeded forward straight [and] level across I-90 until [the] wires broke. At this time I lost control hit a tree and crashed at approximately 7:40 AM. I [immediately] removed seatbelt, helmet, and evacuated aircraft. I ran up to house got owner to call 911 and washed chemical off my skin with garden hose. At this time aircraft burst into flames, which were extinguished by Mitchell Fire [and] Rescue. The pilot stated that there were no mechanical malfunctions during the flight. His recommendation was, "Take ample time to observe all obstacles and give them respect."