On August 23, 2008, at 0900 central daylight time, a Schweizer G-164B, N773D, operated by Sky Tractor Supply, experienced a separation of the right main landing gear following a loss of control while landing at a private airstrip in Nielsville, North Dakota. The commercial pilot was not injured. The airplane sustained substantial damage to the right lower wing and fuselage. The aerial application flight was operating under Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from a private airstrip in Hillsboro, North Dakota, at 0830. The pilot stated he was landing to the north with winds from 290 degrees at 12 knots, gusting to 18 knots. He stated that after touching down he applied the right brake which was "poor" and the airplane turned to the left. The airplane traveled into a wheat field where it contacted a furrow. The pilot stated the airplane bounced up and weathervaned even more. The airplane settled to the ground and the right main landing gear collapsed when it dug into the ground.