The pilot was conducting spraying operations on a pea crop. Swath runs were being made at right angles to a power line and low trees which were located just beyond the end of the crop. On the final run, the aircraft was flown beneath the power line, but the right wing then struck the top branches of a dead tree. The aircraft was seen to climb to about 200 feet, before descending steeply and striking the ground some 370 metres beyond the point of collision with the tree. A fierce fire broke out on impact and engulfed the wreckage. Previous swath runs had almost certainly been made with the aircraft passing above the power line. The reason the pilot chose to fly under the line on the final run could not be established, as there appeared to be no operational reason for this course of action. Expert opinion indicated that after passing below the line, a collision with the tree was virtually inevitable.