Microsphaera penicillata or Erysiphe viburni
- White, powdery fungal growth on both upper and lower surface of leaves
- Tiny round black fungal structures can sometimes be seen within white spots
- Leaves may turn reddish purple or pale yellow around fugal growth
- Leaves may be twisted or deformed by infection
- Common on lower shaded branches, or on shrubs grown in shady areas
- More information on Powdery mildew...