The pilot reported that he was parked at the chemical loading dock, which housed the agricultural spray he was using for his dusting. There was a chemical tank and another airplane parked in front of him. After loading his tanks he proceeded to increase the throttle and turn to the right while watching his left wing to clear the obstacles. The Air Tractor pilot commented that he was not watching his right wing due to the sun. At that time, the pilot of the Aero Commander was stopped on the taxiway and idling, waiting to proceed towards the loading dock. The Aero Commander pilot reported seeing an airplane coming towards him, but assumed the airplane would turn in front of him towards the runway. When the Aero Commander pilot noticed the other airplane was on a collision course with his airplane, he applied throttle to gain the attention of the other pilot, but was unsuccessful. The propeller of the Air Tractor struck the right wing of the Aero Commander, substantially damaging its right wing. The pilots reported that there were no pre-impact mechanical malfunctions or failures with the airframes and engines of their respective aircraft that would have precluded normal flight.