The pilot of the aerial application flight reported that the airplane was loaded with 300 gallons of chemical and 100 gallons of fuel. He stated that all of the instrument readings were good when he powered the airplane up for takeoff. He stated that after liftoff, while in ground effect, a wind shear caused the right wing of the airplane to drop, and the airplane struck a ditch. The recorded wind speed at an airport located 27 miles from the accident site was 7 knots. Postaccident examination of the airplane revealed the fuselage was buckled, and the right wing was bent aft. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.