The pilot carried out one spray run at about 10 feet above the ground in an easterly direction over his own barley crop. The weather was fine with a north-easterly wind of about three knots. The area was very open with large, slightly undulating paddocks. About 40 metres beyond a fence marking the end of the spray run, the left wing struck a single strand power line about 18 feet above the ground. Without breaking, the wire severed a small portion of the upper surface of the wing, near the wing tip. Impact marks on the leading edge of the wing indicate that the aircraft was banked about 30 degrees to the right when it struck the wire. The wire was pulled off three adjacent poles which were about 400 metres apart. The aircraft collided with the ground inverted and nose first about 80 metres beyond the wire. At ground impact there was negligible ground slide. The engine partially dislodged from the airframe and the cabin was partially crushed. The sliding canopy slid open and the home-made hopper ruptured. An estimated 100 litres of herbicide spilled from the hopper. The pilot was not a trained, approved, agricultural pilot. The aircraft was not approved for agricultural operations, nor was the hopper installation. The wire was difficult to see because of the large distance between poles.