On June 11, 1994, at 0925 hours Pacific daylight time, a Grumman G-164A, N8507H, collided with terrain 5 miles west of Bakersfield, California. The aircraft was operated by Vince Crop Dusters I, Buttonwillow, California, and was engaged in aerial application operations. The airplane sustained substantial damage, and the certificated airline transport pilot was seriously injured. Visual meteorological conditions prevailed and the airplane was being operated under visual flight rules. In a telephone interview, the operator stated that the pilot was spraying the field with sulfur dust when he encountered an in-flight fire. The pilot landed in a field and flipped over. The operator indicated that spontaneous combustion of the sulfur had occurred due to high temperatures. In his report, the pilot stated the dust caught fire in the spreader in an explosion like condition. The pilot indicated no mechanical malfunction or failure.