On October 4, 1996, about 1630 Pacific daylight time, N8957Q, a Rockwell S2R airplane, operated by Ag Aviation Equipment, Inc., Pond Creek, Oklahoma, collided with trees and terrain during an emergency descent/landing near Glide, Oregon, and was substantially damaged. The emergency descent/landing was precipitated by a total loss of engine power during normal descent. The commercial pilot, the sole occupant was not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The aerial application flight was conducted under 14 CFR 137. According to the operator in a telephone interview with the Safety Board, the pilot ran out of gas while descending to land after an aerial application. During the forced landing, the airplane struck trees and impacted terrain. The right wing and fuselage were substantially damaged. The operator reported that the airplane's right and left fuel quantity gages read 1/4 tank and 1/2 tank respectively just prior to the accident. In a written statement to the Safety Board (attached), the pilot stated that he thought he had about 30 to 40 gallons of fuel in the airplane, because of the cockpit fuel gage indications. Visual verification of fuel quantity prior to the flight was not performed.