Bacterial leaf spot of Viburnum sargentii

Gail Ruhl, Sr. Plant Disease Diagnostician, Dept. of Botany and Plant Pathology, Purdue University

Viburnum leaves exhibiting dark, angular shaped, water soaked areas may be infected with bacterial leaf spot, also known as bacterial blight. This disease is caused by Pseudomonas syringae pv. viburnii. If infection occurs early in the season, leaves may become distorted. In severe cases, entire shoots can die back.

Infected twigs and buds are potential places for the bacterium to survive the winter. In the spring, when conditions are cool and wet, P. syringae pv.viburniibecomes active, multiplying and infecting the young, sensitive plant tissue.

Management includes removing diseased plant material. This will help reduce the infection potential for the following year. Pruning and good spacing will help to promote good air circulation around plants and aid in drying leaves and branches. Heavy fertilization enhances excessive growth that can be easily attacked by the bacterium. Avoiding this practice will help reduce the amount of material that has the ability to become diseased.  Bactericides containing copper can be used protectively in areas where the disease is an annual problem. Always read and follow label directions.

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Image Courtesy of D. Bertetti