The airplane was departing a rough, unimproved turf strip for an aerial application flight. During the takeoff, the airplane hit a small turf obstruction and became airborne prematurely. The airplane settled and the tail wheel collided hard with the ground followed by the main landing gear. The pilot lost control of the airplane as it porpoised and swerved to the right. He was unable to regain control of the airplane before it ground looped and the wing contact the ground. Substantial damage was sustained to the left wing. No preimpact anomalies were detected with the airplane.