WSU Extension

Hortsense

Caption: Powdery mildew fungal structures on filbert leaf
Photo by: R.S. Byther
  
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Filbert : Powdery mildew
(revision date: 5/20/2014)


Biology
Powdery mildew is a fungal disease found on leaves and succulent shoots of hazelnut. A characteristic powdery white growth occurs on the underside of leaves and sometimes also covers shoot tips. Young growth may be distorted, particularly later in the season. Small, dark fungal structures may be seen in the white mats. The disease often appears late in the growing season. It typically causes little damage. Powdery mildew development is favored by a combination of warm days, cool nights, and humid weather. The fungus can overwinter on the plant and on infected plant debris.
Management Options

Non-Chemical Management
  • Space plantings and prune to provide good air circulation.
  • Plant in full sun.
  • Remove and destroy infected debris beneath trees.
  • Prune out and destroy severely infected shoots when noticed (if practical).
Select non-chemical management options as your first choice!

Chemical Management


In general, powdery mildew is not serious and does not warrant special control measures.

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Caption: Powdery mildew fungal structures on filbert leaf
Photo by: R.S. Byther