Bacterial brown spot
Pseudomonas syringae pv. syringae
More than one symptom can be simultaneously on a single plant.
- Flower blast: flowers and/or flower buds turn brown to black.
- Dead dormant buds, common on cherries and apricots.
- Necrotic leaf spots (entire clusters of younger, expanding leaves may be killed on filbert trees).
- Discolored and or blackened leaf veins and petioles resulting from systemic invasion and infection.
- Spots and blisters on fruit.
- Shoot-tip dieback, which appears as dead, blackened twig tissue extending down some distance from the tip (very common on maples and other seedlings).
- Stem cankers: depressed areas in the bark, which darken with age. A gummy substance often exudes from cankers on fruiting and flowering stone fruits (this symptom is referred to as “gummosis”). If cankers continue to enlarge, they may girdle the stem and subsequently kill a branch or the entire plant. IF the outer tissues of the canker area are cut away, the tissue underneath shows a reddish brown discoloration. This discoloration may also occur as vertical streaks in the vascular tissue.