Prior to the arrival of the aircraft to conduct spraying operations, the loader driver inspected the grass strip surface and informed the pilot that its condition was satisfactory for takeoff and landing. The pilot landed the aircraft and subsequently inspected the condition of the strip himself, before taxiing along the centre of the strip to its western end in order to load the aircraft. He then taxiied to the eastern end and commenced to take off towards the west. The aircraft remained slightly left of the centreline of the strip during the ground roll and encountered an area of soft ground. The pilot lost directional control of the aircraft, which resulted in the left wingtip striking the ground, and the right main landing gear collapsing. A treeline running north-south was located to the west of the strip. A gap in the treeline, slightly left of the strip centreline, was used by pilots during takeoff to ensure obstacle clearance. The pilot reported that he may have been concentrating on the gap during the takeoff ground roll and allowed the aircraft to veer to the left of the intended takeoff path.