THE PILOT WAS ON HIS THIRD DAY OF AERIAL APPLICATION FLYING. HIS TOTAL AERIAL APPLICATION EXPERIENCE CONSISTED OF 5 HOURS, INCLUDING THE ACCIDENT FLIGHT. TOTAL FLIGHT TIME IN TYPE AND MODEL WAS APPROXIMATELY 7 HOURS. THE PILOT WAS OBSERVED FLYING SEVERAL APPLICATION RUNS PRIOR TO THE ACCIDENT. THE AIRPLANE WAS OBSERVED FLYING UNDER POWER LINES DURING ONE OF THE RUNS. DURING THE PULL UP, AT THE COMPLETION OF THE ACCIDENT RUN, A WITNESS OBSERVED THE AIRPLANE'S RIGHT WING STRIKE A TREE. THE AIRPLANE STAGGERED, THEN NOSED OVER AND IMPACTED THE GROUND.