On September 13, 1993, at approximately 0910 hours Pacific daylight time (PDT), a Grumman/Schweizer G-164A, N9536, registered to and operated by Cropland Air Service, Inc., and being flown by Val Woodworth, a certificated commercial pilot, was destroyed during a collision with power lines and terrain while maneuvering during a crop dusting operation approximately five nautical miles south of Dayton, Washington. The pilot sustained minor injuries. Visual meteorological conditions prevailed at the time and no flight plan had been filed. The flight, which was engaged in aerial application of a chemical, was to have been operated in accordance with the requirements set forth in 14CFR137 and originated from the operator's private airstrip near Waitsburg, Washington, at approximately 0900 hours. The pilot reported that following a spray run the aircraft's airspeed began to diminish and that he "added full power (and) pulled out of the canyon." He began a "gradual right hand turn down the canyon" during which a loss of altitude occurred. The pilot reported that "by now I was at tree top level (and) was dodging trees when the aircraft hooked a Bonneville power line." The aircraft collided with terrain immediately thereafter. The aircraft came to rest almost directly beneath the unmarked power lines (refer to photographs 1 & 2). The pilot reported no mechanical malfunction with the aircraft during the event.