How does powdery mildew appear and progress on the vine?

• A. Bright white powder on leaves
• B. Brown patches on fruit
• C. Yellow spots on leaves
• D. Starts as dull grey patches that become black patches as they advance

Answer: (D)

Powdery mildew on grapevines starts as a subtle fungus growth on the leaf surface, often seen as dull gray patches rather than a bright white coating. As the infection deepens, these patches enlarge and the surrounding tissue can die, leading to darker, blackened areas. This progression from gray patches to black patches reflects the advancing severity of the disease and tissue damage, which is why that description is the best fit for how powdery mildew appears and develops. The other patterns describe different symptoms or diseases (such as a bright white powder, brown patches on fruit, or yellow leaf spots) and don’t capture the typical gradual darkening seen as the powdery mildew ages and lesions intensify.