The 16,500-hour commercial pilot was repositioning the tailwheel equipped agricultural airplane to another airstrip located approximately 10 minutes away from his home base. Prior to his departure from home base the pilot reported the winds were from the north at 5 to 6 mph. As the pilot entered the traffic pattern for the landing airstrip on a southbound downwind leg, he noticed that the winds were still from the north; however, they were now gusting from 10 to 15 knots. The pilot, who was very familiar with the airstrip, reported that when landing to the north, he prefers making a long final approach to avoid all obstacles while making a short field landing to avoid rolling over a gravel covered portion of the airstrip. The pilot stated that he lined-up and touched down slightly west of the centerline, and as the aircraft crossed over the south bank of a 30 to 40 foot wide ditch running short of runway, the aircraft encountered a 'large wind gust.' The pilot attempted to add power to compensate; however, the turbine engine took too long to spool up. The airplane impacted the north bank of the ditch and both main landing gears separated from the airframe. The airplane came to stop on a northwesterly heading after sliding for 30 to 40 feet. The pilot reported having accumulated a total of 385 hours in the same make and model, with about 285 hours in the preceding 90 days.