Which of the following diseases is commonly found in greenhouse plants?

The presence of powdery mildew, botrytis, and root rot in greenhouse plants highlights the types of diseases that frequently affect plants grown in controlled environments. Greenhouses provide ideal conditions for diseases to thrive, such as increased humidity and potential crowding of plants, which contribute to the spread of fungal pathogens.

Powdery mildew is a fungal disease that typically manifests as white, powdery spots on leaves and can spread rapidly in warm, dry conditions. Botrytis, or gray mold, is another fungal issue, often affecting flowering plants and can lead to significant losses if not managed properly. Root rot, primarily caused by overwatering and poor drainage, is a common issue for greenhouse plants due to the constant moisture levels.

The other options mention diseases that are less commonly associated with greenhouse environments or may not pose as significant a threat as the diseases listed in the correct choice. This choice thus effectively represents the reality of disease pressures that greenhouse managers must frequently monitor and manage.