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Rhododendron Blight

Rhododendron Blight is caused by a fungus: flower buds do not open, turn brown and rot under the influence of rain.

Also known as:
Bud blast

Do not confuse with:
Frost damage of the buds

recognize Rhododendron Blight
Rhododendron Blight, photo: Rob Tjalkens

Rhododendron Blight is caused by a fungus (Pycnostysanus azaleae or Seifertia azaleae). Flower buds do not open, turn brown and rot under the influence of rain. At a later stage, the brown buds are covered with black fungal dots. The buds remain on the branches.
The fungus is spread by the Rhododendron leafhopper (Graphocephala fennahi), which has been active in Europe since the second half of the last century.
The leafhopper and the larvae themselves do little damage to rhododendrons.

If not only the flower buds are affected but also leaves, stems and branches then the fungus Botrytis cinerea, a variant of gray mold is active.

Where to find

  • Rhododendron
  • Azalea

Control

Remove affected buds regularly. To prevent the spread of the fungus, do not put the affected buds on the compost pile but with the kerbside garden / food waste or burn them.

Prevention

Catch Rhododendron leafhoppers away because they spread the fungus. A bird-friendly environment also helps.