Viburnum Diseases: Canker, Mildews, and Management

Key Diseases of Viburnum Shrubs

Viburnums are popular landscape shrubs that can be affected by several fungal diseases. Proper cultural practices and timely interventions keep them healthy.

Botryosphaeria Canker

Symptoms: Leaves on affected branches wilt and die; branches die back and become covered with dark-brown to black pimple-like fungal fruiting structures; wood under bark is dark brown.

Pathogen: Botryosphaeria species.

Management: Plants under drought stress are most susceptible. Irrigate to prevent drought stress. Prune out infected branches.

Downy Mildew

Symptoms: Angular spots limited by leaf veins form blotches that die and shrivel in wet spring weather; severely affected leaves fall; light-colored fungal growth sparsely covers spots on leaf undersides.

Pathogen: Plasmopara viburni.

Management: Rake and destroy fallen leaves in autumn. Avoid overhead irrigation in spring. Apply fungicide as soon as disease is observed.

Powdery Mildew

Symptoms: White fungal growth on upper leaf surfaces.

Pathogen: Erysiphe or Phyllactinia species.

Management: No control recommended as little damage occurs. If severe, apply a fungicide.