After the interim completion of agricultural spraying operations, the property owner asked the pilot to disperse one load of insecticide over a neighbour's property. The adjacent property owner had requested this work to be done. As the pilot hover-taxied an Agusta-Bell 47G-3B1 helicopter towards a water replenishing point on the neighbour's property, the cockpit bubble and one main rotor blade of the helicopter struck an unseen single strand high-tension power line partially concealed by a shed. The pilot was able to maintain control of the helicopter and landed safely. The helicopter sustained minor wire impact damage to one main rotor blade, the main rotor mast, and one tail rotor blade. The pilot and passenger escaped without injury. The water tanks were near a shed which partially concealed the wire which was at an angle of about 45 degrees to a height of 60 to 70 feet AGL. The wire also blended into the background foliage. The pilot had visited this section of the neighbour's property about 2 years ago. No wires were noted during this visit. The owner of the adjacent property had not briefed his neighbour to inform the pilot about a new wire that had been erected near the water tanks. Consequently, the pilot had not been adequately briefed by the other property owner as to the presence and location of the recently erected wire which was in close proximity to the water tanks.