The aircraft was engaged in night spraying of cotton crops. The pilot had completed about two and one half hours work on two properties, with a short break between tasks, before arriving at 'Ginidgeree'. The night was clear but dark, with a barely discernable horizon on certain headings. The marker vehicles had assumed their positions at each end of the first spraying run when the aircraft arrived over the paddock. Believing the markers to be incorrectly positioned, the pilot elected to fly orbits over the paddock while clarifying his orientation. After several orbits the pilot accepted the marker positions and the aircraft departed to the north to begin the approach for the first spraying run. During the turn to intercept the inbound track, the aircraft struck a tree then impacted the ground and continued forward for 130 m, shedding components and starting a fire. The pilot suffered minor injuries and evacuated the burning wreckage without assistance. The aircraft had struck the tree in a gentle descent during the turn. The pilot, believing that the aircraft was flying level, did not notice the descent as he was concentrating on lining up for the first spraying run. The pilot held a Commercial Pilot Licence which had been endorsed for night spraying six days earlier. He had about 700 hours experience in agricultural flying, including about 50 hours of night spraying, in Agwaggon and Airtractor aircraft. At the time of the accident, the pilot was wearing overalls, boots, a high quality helmet and was tightly strapped into his seat. Damage to the helmet indicated multiple impacts including at least one of extreme severity. In laboratory tests conducted overseas, a force of over 300 g was required to produce damage similar to that on the helmet. It is almost certain that, without the helmet, the pilot would not have survived the accident.