On August 20, 1996, at 1110 central daylight time (cdt), a Grumman G-164A Agcat, N904X, piloted by a commercial pilot, was substantially damaged during a collision with trees and the ground. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 137 flight was not operating on a flight plan. The pilot reported minor injuries. The flight departed Kewanee, Illinois, at 1045 cdt. During an interview the pilot said he was trying to fly parallel to an uneven tree line next to the field he was going to spray. He said the airplane collided head-on with the trees. After the collision the pilot said he pitched the airplane up at a high angle of attack. Shortly after pitching up the airplane struck the trees a second time, followed by a collision with the ground. The pilot said this was his first accident during 39 years of flying. He said his reaction time was not as quick as it should have been. The pilot said the trees his airplane collided with protruded into the corn field about 300 feet from its border.