The helicopter pilot reported that, after the fourth aerial application flight of the day, he landed and positioned the helicopter near the autoloader boom truck. He reduced engine power to flight idle and the ground crew began the loading process. He verified the collective position was full down, set the cyclic friction to ON, and exited the helicopter to stretch while maintaining one hand on the cyclic. Immediately after, while standing next to the helicopter, he heard two "loud bangs." He immediately boarded the helicopter; the ground crew secured the boom, and the pilot shut down the engine. Upon further examination by the operator's maintenance personnel, it was determined that a main rotor blade struck the boom arm and that the main rotor blades were beyond the repair limitations, per the manufacturer's guidance. The helicopter sustained substantial damage to the main rotor blades. The director of aerial operations reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The director of aerial operations added that, at the site of the accident, the wind was 130º at 11 knots, gusting up to 19 knots. The helicopter was oriented with a southbound heading.