On May 21, 1996, at 1130 central daylight time, a Cessna 188, N2062J, operated by Slater Spraying Service, Inc., sustained substantial damage during takeoff roll. The 14 CFR 137 flight lost control while departing a two lane county road, and nosed over in the ditch west of the road. The commercial pilot was not injured. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported the winds were northwesterly at 8 to 10 knots, gusting from 15 to 20 knots. He reported that he departed the county road to the north. He reported that a gust of wind caused the airplane to weathervane. He ran out of right rudder and was unable to maintain directional control. The airplane flew over the ditch which paralleled the road and landed in a field. The right wheel pulled the airplane back toward the ditch. The pilot reported that when the main wheels hit the water in the ditch, the airplane nosed over.