Symptoms and recognition (Apple powdery mildew)

Primary blossom mildew

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.