Powdery Mildew of Blueberry


Powdery Mildew

Yellow to black fruiting
bodies (cleistothecia) form on infected
leaves. Photo courtesy of
NCSU Cooperative Extension Service

The powdery mildew disease usually does not develop on blueberry leaves until midsummer after the crop is harvested.


  • A white fungus growth on the upper leaf surface of some cultivars, or it may be indistinct and confined to the lower leaf surface.
  • Chlorotic spots with reddish borders are common on the leaf surface and may be mistaken for symptoms caused by the red ringspot virus.
  • The leaves show light green, yellow or reddish areas and puckering.
  • Water-soaked spotting is visible on leaf undersides. In severe cases, plants may defoliate.

Disease cycle:

  • At the end of summer, yellow to black fruiting bodies (cleistothecia) form on infected leaves.
  • Airborne spores released by cleistothecia in the spring infect young leaves.
  • The mycelium is superficial and penetrates only the epidermis. Powdery Mildew Image goes HERE.
  • Secondary spores are produced on the leaves and dispersed by wind throughout the summer.
  • High temperatures and humidity promote disease development.

Disease Management

  • Plant resistant cultivars.
  • Reduce humidity in the planting.
  • Use fungicides if the disease is severe.