On August 2, 2002, about 1030 central daylight time, a Cessna A188B, N4723Q, registered to and operated by Valley Air Applicators, Inc., collided with an unmarked power line during a spray run near Indianola, Mississippi. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 137 aerial application flight. The airplane was substantially damaged and the commercial-rated pilot, the sole occupant, was not injured. The flight originated about 1005, from the Indianola Municipal Airport, Indianola, Mississippi. According to the operator, during a spray run of a cotton field, the airplane collided with an unmarked power line. The pilot then immediately landed in the cotton field. The operator also stated that the pilot was familiar with the field he was spraying and thought that the airplane was clear of power lines so he initiated a climb, resulting in the contact. Postaccident examination of the airplane revealed that approximately 1 foot of the vertical stabilizer and rudder assembly were separated. Additionally, arcing was noted on the right wing lift strut, and the propeller was damaged.