Informational table showing disease name, symptoms, pathogen/cause, and management of Viburnum diseases. Disease Symptoms Pathogen/Cause Management Botryosphaeria canker 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 the bark is dark brown. Botryosphaeria Plants most susceptible are those under drought stress. Therefore, irrigate to prevent drought stress. Prune infected branches. Downy mildew Angular spots limited in shape by the leaf veins form blotches that die and shrivel in the spring when the weather is wet. Severely affected leaves fall. Light- colored fungal growth sparsely covers the spots on the underside of the leaf. Plasmopara viburni Rake and destroy fallen leaves in the autumn. Avoid overhead irrigation in the spring. Apply a fungicide as soon as any disease is observed. Powdery mildew White fungal growth forms on the upper surface of leaves. Erysiphe or Phyllactinia No control is recommended since little damage occurs. If severe, apply a fungicide.