On August 19, 2003, at 1700 central daylight time, a Piper PA-25, N4346Y, operated by Reabe Flying Service, sustained substantial damaged on impact with a corn crop and terrain near Brandon, Wisconsin, during a spray pass over the field. The commercial pilot was not injured. The 14 CFR Part 137 aerial application flight departed from Waupun Airport (WI07), Waupun, Wisconsin, on a local flight. Visual meteorological conditions prevailed. No flight plan was filed. The pilot reported that approximately 70 gallons of chemical remained as he was making the aerial swath before the accident. He reported the winds were from the south at 9 knots gusting to 14 knots, and the temperature was 88 degrees Fahrenheit. He reported the airplane was descending over a treeline heading southbound when it experienced moderate turbulence. He reported that he was "unable to stop the descent before the airplane made contact with the corn." The airplane continued it's descent and the nose of the airplane impacted the ground and the airplane skidded to a stop. The pilot reported there was no mechanical malfunction of the airplane prior to the accident.