The airplane was landing on a grass strip toward the west. The pilot stated that the airplane touched down on the centerline of the runway and was slowing down when the airplane encountered a strong gust of wind from the right. The pilot was unable to correct for the gust of wind and the airplane impacted trees on the left side of the runway. Examination of the airplane revealed that the right wing spar was broken, and the left wing spar was bent. The pilot stated that there were no mechanical malfunctions or failures that would have precluded normal operation. The wind at the time of the accident was recorded as 090 degrees at 9 knots.