Match the symptom to the cause before acting. Green mould in bags: poor straw treatment, old spawn or low pH. Long stalks, small caps: high CO2 or low light. Pale yellow caps: light under 100 lux. Brown caps in sajor-caju: temperature above its band. Wet, rotting caps: water left on the surface. Larvae in stalks: flies got in; screen with 35 mesh net, use a light trap, and cover spent bags in the pit with at least 10 cm of manure.
This course gives no spray recipes. Hygiene, air, light and temperature fix most of the above. If a product is used, check current label approval and keep the 48-hour gap between spraying and picking that NHB requires.