Powdery mildew is commonly caused by what type of organism and appears as white powder on leaves?

• A. Powdery mildew
• B. Late blight
• C. Fire blight
• D. Powdery bacteria

Answer: (A)

Powdery mildew is caused by fungi. The white powder you see on leaves is the dusty coating of fungal spores (conidia) produced by these fungi as they colonize the leaf surface. This powdery appearance is a hallmark of powdery mildews and helps distinguish them from other diseases. For example, late blight is caused by an oomycete and tends to show water-soaked or greasy lesions, while fire blight is a bacterial disease that causes cankers and wilting. The option that names powdery mildew points to the fungal cause behind the characteristic white, powdery coating, making it the best fit.