Which conditions are favorable for powdery mildew?

• A. Cold temperatures, full sun
• B. High humidity and heavy rainfall
• C. Optimal temperature 25C, shade, can thrive in dry conditions
• D. Wet and windy

Answer: (C)

Powdery mildew grows best in warm, moderate temperatures with enough humidity but without leaf wetness. About 25°C is near optimal, and the fungus prefers areas with some shade where direct sun doesn’t overheat and desiccate the leaf surface. It can tolerate dry leaf surfaces, because it doesn’t require free water on the leaf to spread, unlike many other fungi that need leaf moisture. Heavy rainfall or constant wetness disrupts the disease by washing away spores and creating conditions less favorable for its growth. Direct sun also tends to inhibit it by reducing humidity and drying the canopy.

So the description of an around-25°C temperature, shade, and dry conditions best matches how powdery mildew behaves, making that option the most favorable.