Black Spot of Roses is caused by which type of organism?

• A. Fungus
• B. Bacterium
• C. Virus
• D. Nematode

Answer: (A)

Black Spot of Roses is caused by a fungus. The disease produces round black spots on rose leaves, often with a yellow halo, and it spreads when fungal spores are released in moist, humid conditions. Fungi routinely cause leaf spots with spores that move in rain splash and prefer wet leaf surfaces, which fits how Black Spot behaves in the field. Other types of pathogens produce different symptoms: bacteria tend to cause greasy or water-soaked lesions, viruses cause mosaic patterns or distortion, and nematodes affect roots or crowns rather than creating the distinctive leaf spots. Because this disease is fungal, management focuses on reducing leaf wetness and leaf-to-leaf contact, removing and destroying infected tissue to lower inoculum, improving air circulation, and applying fungicides during periods of high humidity or after rain to protect new growth.