Powdery mildew occurs wherever apples are grown, and is generally always a problem in tree nurseries.
- However, economic loss from mildew varies with climatic conditions.
- It is generally a serious disease in the UK, particularly the eastern part but usually less of a problem in the west.
- Mildew is also not usually a serious problem in Europe, particularly in Northern Europe where the cold winters usually result in death of overwintering mildew.