The pilot of the tailwheel-equipped airplane reported that, during the landing roll, a gust of wind pushed the airplane to the left. The pilot added partial throttle to enhance rudder effectiveness, but was unsuccessful. The airplane veered to the left, exited the runway, and impacted a ditch. The airplane sustained substantial damage to the right wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The automated weather observation station located 10 miles west of the accident airport reported that, about 31 minutes before the accident, the wind was from 180° at 13 knots, gusting to 22 knots. The same automated station reported that, about 29 minutes after the accident, the wind was from 200° at 16 knots, gusting to 23 knots, peak wind, 4 minutes before the accident, from 190° at 27 knots. The airplane landed on runway 18.