The pilot reported that he was conducting a low reconnaissance flight prior to helicopter aerial application operations; during the low reconnaissance, the helicopter came in contact with a power line which caught on the left skid. The pilot further reported that, while under tension, a section of the power line "snapped" into the main rotor system resulting in a loss of control. Subsequently, the pilot performed an emergency autorotation to a wheat field which resulted in a hard landing followed by main rotor contact with and consequent separation of the tail boom. The fuselage and the tail boom were substantially damaged. The pilot reported there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. As a safety recommendation, the pilot reported that a more thorough high reconnaissance flight prior to the low reconnaissance flight would have decreased the probability of this accident occurring.