Every route into the room has a cheap physical answer. Air: ICAR-DMR recommends 2 micrometre mesh filters on fresh-air entry points to hold back mould spores. Flies: NHB says screening doors and ventilators with nylon net of 35 mesh or finer checks their entry. Casing: ICAR-DMR's wet bubble folder gives steam at 54.4 °C for 15 minutes; the manual's general casing pasteurisation is 60 to 65 °C for 6 to 8 hours. Spent compost: NHB says put it in the pit under at least 10 cm of manure to stop fly breeding.
People and tools are the last route. A foot dip, crates kept to one room, and visiting the sick crop last need no product at all.