On July 25, 2012, about 1245 central daylight time, a Scotts-Bell 47 Inc. 47G-2A helicopter, N73252, was substantially damaged when it impacted terrain while spraying a potato field near Akeley, Minnesota. The commercial pilot sustained minor injuries. The helicopter was registered to and operated by Scotts Helicopter Service, Inc., under the provisions of 14 Code of Federal Regulations Part 137, as an agricultural application flight. Day visual meteorological conditions prevailed and no flight plan was filed. The pilot reported he was on a “clean up” pass and descending into the field, over a set of 20 foot power lines, when he experienced a slight yaw to the right and felt a slight vibration that seemed to be coming from the rear of the helicopter. When he began to apply left pedal input the helicopter immediately entered an excessively nose low attitude with an increased yaw to the right. After the pilot applied aft cyclic control the helicopter impacted terrain and came to rest on its left side. The fuselage, tail boom, and main rotor were bent, crushed, and wrinkled. The tail rotor gear box and tail rotor separated from the helicopter. One separated tail rotor blade was observed 50 feet to the north of the main wreckage and the other blade was observed 50 feet to the south of the main wreckage. An examination of the helicopter and its systems revealed no preimpact anomalies and there was no evidence of a wire strike. The source of the vibration could not be determined.