On August 13, 2008, at 1430 central daylight time, an Air Tractor AT-301B, N3161D, collided with trees during an off airport forced landing in Monticello, Iowa. The pilot received minor injuries. The airplane received substantial damage to the wings. The aerial application flight was operating under Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from the Monticello Regional Airport (MXO) at 1235. The pilot reported he completed the aerial application portion of the flight and was returning to MXO when the engine suddenly lost power. He stated he was at an altitude of about 200 feet above the ground and had no option but to land the airplane in the trees. The pilot reported he had approximately 75 gallons of fuel on board when he took off. The pilot stated the airplane typically consumed approximately 40 gallons per hour. The pilot reported to a Monticello Police Sergeant that he believed the airplane ran out of fuel. Inspection of the accident site revealed the fuel tanks were ruptured and empty. First responders to the accident site reported there was no odor of fuel having leaked from the airplane.