The pilot reported that while in cruise flight, about 500 feet above ground level (agl), the cyclic control seemed to require a higher than normal input. He changed speed, however, that seemed to make it worse. The pilot was over a field and entered a 180 degree autorotation to lose altitude. At the completion of the autorotation, forward velocity had dissipated and the lateral movement to the left increased even with full right cyclic input. The helicopter collided with trees that bordered the field and subsequently rolled over onto its left side after touchdown. The fuselage and tailboom were substantially damaged.