Red Seal Landscape Horticulturist Practice Exam

What is a common disease affecting roses in landscaping?

1. Powdery mildew

2. Botrytis blight

3. Black spot disease

4. Root rot

The correct answer is: Black spot disease

Black spot disease is a prevalent fungal infection that significantly impacts roses in landscaping. This disease is caused by the fungus Diplocarpon rosae, which thrives in wet and humid conditions. Black spot manifests as dark, circular spots with fringed edges on the upper sides of leaves, leading to premature leaf drop and overall decline in plant health. Understanding black spot disease is essential, especially for rose maintenance, as its presence can weaken the plant and reduce its flowering capacity. Effective management involves selecting resistant rose varieties, ensuring proper air circulation to reduce humidity, and applying fungicides as needed. This disease is notorious among rose cultivators and landscape professionals, making it a common and critical topic of consideration in horticulture. While powdery mildew, botrytis blight, and root rot are also diseases that can affect plants, they do not specifically align with the most prominent issue faced in roses. Powdery mildew, for instance, tends to occur in conditions of high humidity but is not as frequently a challenge as black spot. Similarly, botrytis blight, while concerning, primarily targets flowers and stems rather than leaves to the same extent that black spot does. Root rot, on the other hand, is primarily associated with waterlogged conditions affecting a plant's root