THE AGRICULTURAL SPRAYING OPERATION WAS BEING CONDUCTED OFF OF A HARD SURFACED COUNTY ROAD. IT BEGAN TO RAIN, SO PILOT LANDED ON ROAD TO WAIT FOR RAIN TO STOP. A THUNDERSTORM WAS APPROACHING FROM THE WEST AND THE WIND BEGAN TO INCREASE AND GET GUSTY. THE PILOT DECIDED TO TRY TO TAKEOFF TO THE WEST AND RETURN TO AIRPORT. THE CROSSWIND WAS FROM THE SOUTHWEST. ON TAKEOFF PILOT COULD NOT MAINTAIN DIRECTIONAL CONTROL. THE AIRCRAFT BECAME AIRBORNE, DRIFTED TO THE RIGHT, SETTLED INTO DITCH, AND NOSED OVER.