THE PILOT REPORTED THAT HE WAS SPRAYING A FIELD AND WAS HAVING A PROBLEM WITH THE AUTOMATIC FLAGGER. HE HAD COMPLETED A PASS AND PULLED UP WHEN HE NOTICED SOMETHING DIFFERENT ABOUT THE FLAGGER. HE REPORTED HIS ATTENTION WAS DIVERTED FROM FLYING AND HE FAILED TO CLEAR TREES. THE AIRPLANE CONTACTED THE TOPS OF THE TREES. CONTROL OF THE AIRPLANE WAS LOST AND IT IMPACTED IN A FIELD. THE AIRPLANE CAUGHT FIRE SHORTLY AFTER IMPACT AND BURNED.