On September 21, 1995, about 0800 eastern daylight time, N7304C, an Air Tractor AT-301A, operated by Indian River Flying Service experienced a hopper fire in flight and crashed in Vero Beach, Florida, while on a 14 CFR Part 137 agricultural flight. Instrument meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The pilot received minor injuries and the airplane was destroyed by fire. The flight had originated about 20 minutes earlier. The pilot reported and a witness observed the hopper catch on fire in flight. The pilot executed an emergency landing to a road between trees in an orange grove. The hopper was filled with sulfur dust. Examination of the airplane's logbooks by an FAA inspector produced no recorded entries of compliance with Airworthiness Directive(AD) 48-34-02, which is applicable to all aircraft engaged in sulfur dusting. This AD lists five fire prevention measures that must be complied with before engaging in sulfur dusting operations. The following measures are:[1] location of engine exhaust,[2] bonding of fuselage,[3] agitator bearing design/maintenance,[4] hopper gate construction/material,[5] fire resistant lower fuselage.