Which plant is highly susceptible to powdery mildew?

The correct answer is Hosta, which is notably highly susceptible to powdery mildew. This fungal disease is characterized by a white or gray powdery growth on leaves and stems, particularly in warm, dry conditions. Hostas, being shade-loving plants, often thrive in environments that can promote high humidity, creating an ideal setting for powdery mildew to develop. The dense foliage and the tendency for these plants to retain moisture can further exacerbate the likelihood of infection.

While other plants such as Azalea, Crepe Myrtle, and Boxwood can also experience various fungal diseases, they are not as commonly affected by powdery mildew as Hostas. The specific leaf structure and growth habits of Hostas make them particularly prone to this pathogen, emphasizing the need for preventive measures like proper spacing, air circulation, and managing moisture levels to mitigate the occurrence of powdery mildew.