SHORTLY AFTER TAKEOFF THE AIRPLANE WAS OVER A WOODED AREA IN A RIGHT TURN INTO THE FIELD TO BE SPRAYED WHEN A TOTAL LOSS OF ENGINE POWER OCCURRED. AS THE PILOT DUMPED THE LOAD, THE AIRPLANE ENTERED A ROLL. THE AIRPLANE IMPACTED 75 FOOT TALL TREES AND TERRAIN. ON SITE EXAMINATION REVEALED FUEL TANK INTEGRITY WITH NO FUEL AVAILABLE IN THE TANKS. AN EXAMINATION OF THE ENGINE DID NOT REVEAL ANY ANOMALIES THAT WOULD HAVE CONTRIBUTED TO THE POWER LOSS.