On July 19, 2013, about 0807 central daylight time, an Air Tractor AT-400, N155HF, sustained substantial damage when it impacted a guy wire and subsequently impacted the terrain near Steward, Illinois. The commercial pilot, the sole occupant, was seriously injured. The airplane was registered to Woodley Aerial Leasing LLC and operated by the pilot under the provisions of the 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight originated from a local airstrip about 0740.The pilot reported that he circled the field to check for obstacles prior to beginning the application pass, but he did not see the guy wires reaching further into the field than he was normally accustomed. He made the first pass without incident, and then during the second pass the airplane hit the guy wires "head on." The airplane impacted the cornfield, and two towers were toppled by the impact with the guy wires. The pilot reported that there was no malfunction or system failure of the airplane before the accident.