On October 25, 2002, at 1500 central daylight time, an Air Tractor AT-602 agricultural airplane, N602GB, was substantially damaged upon collision with the guy wire from a radio station transmission tower while maneuvering near Plainview, Texas. The airline transport pilot, sole occupant of the airplane, was not injured. The airplane was owned and operated by G.B. Aerial Applications, Inc., of Plains, Texas, under 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed for the local aerial application flight for which a flight plan was not filed. The local flight originated from the operator's home base in Plains, Texas, approximately 30 minutes prior to the accident. The pilot reported to the FAA inspector, who traveled to the accident site, that he had just completed spraying a field west of the radio station tower and climbed a few hundred feet to program the on-board Global Positioning System (GPS) prior to proceeding to the next field to be sprayed. The 15,000-hour pilot reported that while en route to the next field, the leading edge of the right wing collided with a guy wire from the recently erected radio station transmitter tower for radio station KLZK-FM 97.3. The pilot reported that the impact with the guy wire resulted in a momentary loss of control and the airplane abruptly turned about 90 degrees towards the south. The pilot was able to regain control of the airplane by applying "almost full aileron and full rudder deflection." The airplane continued a flight path straight ahead, and the pilot located a suitable landing area. The pilot made an uneventful precautionary landing in an open wheat field approximately one mile southeast of the tower. A Deputy Sheriff for the Hale County Sheriff Department witnessed the airplane's collision with the tower and observed the tower collapsing to the ground. He was the first to respond to the accident site. Examination of the 1997- model PT6 powered airplane by the FAA inspector revealed that the right wing was displaced aft at the wing root, resulting in structural damage to the fuselage at the wing mount attaching area. Additionally, the leading edge of the right wing, the right aileron, the right wing flap, and the right hand spray boom were damaged. The restricted category airplane, serial number 602-0425, was equipped with an aerial application system for the eradication of the boll weevil. The airplane was reported to have impacted the 756-foot transmission tower at about the 500-foot level. The tower was not depicted on the Dallas Sectional Chart; however, it was listed in the current Aeronautical Chart Bulletin in the Airport/Facility Directory. The tower was knocked down and was reported as "destroyed." There were no reported injuries to anyone on the ground. At 1545, the weather observation facility at Plainview (PVW) reported winds from 250 degrees at 8 knots, a ceiling of 1,100 feet overcast, visibility of 4 statute miles in haze, a temperature of 12 degrees Centigrade, with a dew point of 10 degrees Centigrade. The altimeter setting was reported as 29.99 inches of Mercury. The Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) was not submitted by the pilot or the operator; however sufficient statements and information were provided by the pilot and the operator to support the accident investigation.