The bacterium multiplies in buds and on expanding aerial plant tissues as an epiphyte during the late fall and into the spring months. 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.
Only canes produced the previous season are attacked. The pathogen is rarely isolated from asymptomatic tissues during dry weather but can be isolated from symptomatic, diseased tissues year-round.
Additionally, P. syringae has been reported to colonize weeds and grasses. The disease is favored by presence of overwintering inoculum in diseased stems and buds on plants in the field.
The first symptoms may appear in January and early February due to a winter injury. Aside from brown and black cankers, the most common symptom is dying sprouts. Other symptoms included reddish-brown to black irregular cankers on the shoot tips that extended downward along the branches.
In some plants, cankers surrounded the stem, causing shoot-tip dieback and necrosis of the buds. Cankers can extend the entire length of the stem or girdle stems. Buds in or above the canker area are killed.
Bacterial canker in blueberry plants
