Willow Watermark Disease

Willow watermark disease Common name Willow watermark disease Causal agent Watermark disease is caused by a bacterial pathogen belonging to the genus Brenneria, which mainly contains pathogens of woody plants. Scientific name Brenneria salicis Symptoms & Signs The initial symptom of willow watermark disease is wilting and reddish discoloration of the leaves. Trees older than four years are at a greater risk of attack. Branch dieback and disruption of the xylem tissues are common symptoms of the disease. When the branches are cut transversely, or the bark is peeled off, a reddish-brown stain or the watermark is clearly visible. Wood sap containing the bacterial pathogen is also seen near the junction of the branches. Transmission The bacteria present on the leaves and stems enter the plants through openings such as stomata and wounds. Using infected tools during propagation and pruning can also spread the disease to healthy plants. Time of concern Early spring to summer Common hosts Willow trees