The pilot was engaged in spraying an area of grape vines. On the final spray path the aircraft had to pass under a set of power lines. The pilot reported that as the aircraft approached the power lines, it was affected by an updraught. He pushed the control column forward but the propeller and fin mounted wire deflector struck the power lines. The aircraft descended and struck a post used to support the vines before it came to rest in the crop. The pilot was inexperienced in agricultural operations. The final spray run involved a difficult task in that several obstacles had to be negotiated. It is probable that the aircraft was affected by a willy willy and that the pilot was unable to fully regain control of the aircraft before it struck the crop.
