How can downy mildew be managed?

• A. Sprays made from copper salts (Bordeaux) with protection lasting until 20 mm of rain has fallen
• B. Other fungicides
• C. Good drainage and an open canopy that dries quickly
• D. None of the above

Answer: (C)

Downy mildew needs leaf wetness to infect, so the most effective management focuses on reducing that wetness and drying leaves quickly. Good drainage prevents water from lingering on the soil and surrounding foliage, while an open canopy promotes airflow and faster drying after rain or dew. This combination minimizes the time leaves stay wet, cutting down on infection opportunities and sporulation cycles.

Copper-based sprays can provide a protective barrier, but their effectiveness is weather-dependent and can be washed off by rain, making them less reliable as the sole strategy. Other fungicides exist, but without addressing the microclimate—how long leaves stay wet—the disease can still spread.