The pilot was performing a take-off in crosswind conditions of about 15 knots. When the aircraft had reached a speed of about 40 knots it suddenly veered to the left, and despite corrective action the pilot was unable to maintain directional control. With full power still applied, the aircraft ran off the side of the strip. It then passed over an embankment, and travelled a further 200 metres before colliding with trees which were some 60 metres from the edge of the strip. The initial loss of directional control was associated with a wind gust in excess of the maximum for the capabilities of the aircraft. The pilot had persisted with the take-off attempt after the aircraft ran off the strip, because he considered that to have reduced power would have caused the aircraft to ground loop. He had endeavoured to dump the load, but had initially inadvertently applied the spray handle. As a result, only about 10 of the load had been dumped before the collision with the trees.