The field where this accident occurred had been sprayed one week prior to the accident by a fixed-wing aircraft at an altitude of 20 feet. No wires were noted to be a hazard at that time. On the day of the accident, the pilot of the helicopter was talking to a spotter on the ground via radio. Neither person noticed the power lines crossing one end of a small section of the corn field. The helicopter struck the wires on his first pass. They became entangled in his rotor control rods and the machine settled to the ground. The pilot stated that the reason neither he nor his spotter saw the wires was because they were strung in a non-standard manner in that the non-supported span of wire was excessive. The wires drooped to 7 feet above the corn. Also, there were no guy wires or transformers on the poles to indicate a power line array. This pilot has over 5,600 hours of aerial application flying time in his logbook.