Pseudomonas syringae is a naturally present environmental bacterium that can survive on the surface of the stem; it only infects the plant if it enters the stem through wounds, such as from frost damage, or through natural openings, such as leaf scars.
The bacterium multiplies in buds and on expanding aerial plant tissues as an epiphyte during the late fall and into the spring months.
Cankers can extend the entire length of the stem or girdle stems. Cankers can kill buds, and if a canker girdles the stem, the stem portion above the canker dies. Leaves turn orange (or black) and wilt after buds have leafed out.
Bacterial canker can be particularly severe on young plants in new plantings because a high proportion of the wood is succulent and susceptible to disease.
The bacteria survive on the buds and bark and enter the plant through wounds caused by frost or pruning. Only 1-yearold stems are attacked. The bacteria can be spread by wind, rain, insects, propagation wood, and pruning tools.
Disease severity and symptom expression is favored by factors including poor nutrition, plant parasitic nematodes, sandy soils, and by climatic factors such as late spring frosts and cool, wet growing conditions.
Bacterial canker of blueberry plant
