Apple leaves, blossoms and fruit can be affected.
Primary blossom mildew
- This emerges at pink bud.
- Flowers are deformed with pale green or yellow petals and with petals and rosette leaves covered in white mycelium and spores.
Primary vegetative mildew
- This emerges when extension growth starts.
- These infected terminals are usually stunted, with small leaves also covered in mildew mycelium and spores).
- In winter affected shoots appear as silvered shoots.
Secondary mildew
- On leaves infections appear first as whitish felt-like patches of fungal mycelium and spores, usually on the underside.
- These lesions may appear as chlorotic spots on the upper leaf surface.
- The leaf may also be distorted.
- Badly affected leaves usually fall prematurely.
- Young fruitlets are also susceptible to infection. Mildew appears on these as a fine network of mycelium resulting in net-like russet.
- On some varieties white mycelium may also be obvious on fruit.
Other problems that may be confused with mildew
- Mildew symptoms though not always easy to recognise, are fairly distinctive.
- Fruit russet may be caused by other factors such as weather or chemicals.
- Usually russet caused by mildew is distinguishable by its fine net-like appearance.