THE PLT SAID THAT HE WAS COMPLETING AN AERIAL APPLICATION OPERATION WHEN THE ENGINE FAILED. AN EMERGENCY LANDING WAS ATTEMPTED ON ROUGH TERRAIN WHICH RESULTED IN SUBSTANTIAL DAMAGE TO THE ACFT. POST ACCIDENT INVESTIGATION REVEALED CATASTROPHIC FAILURE OF THE INTERNAL ENGINE COMPONENTS DUE TO OIL STARVATION. THE REASON FOR THE OIL STARVATION COULD NOT BE DETERMINED DUE TO THE EXTENT OF THE INTERNAL DAMAGE.