Bacterial leaf spot
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.
Click image to enlarge
Image Courtesy of D. Bertetti