Which of the following is a valid route by which rose black spot can spread?

• A. Water and wind.
• B. Direct contact.
• C. Seeds.
• D. Soil contact.

Answer: (A)

Rose black spot spreads via fungal spores that form on infected leaves and are carried to other plants by environmental forces that move moisture and air. When leaves are wet from rain or overhead watering, spores are splashed onto nearby leaves, starting new infections. Wind can also carry airborne spores to other plants. Because the spread relies on moisture-driven splash and air movement, water and wind is the route that best explains transmission. Seeds don’t typically carry or initiate infection for this disease, and infection almost never starts from soil contact or direct contact between plants in the way this pathogen spread is usually defined.