Pseudomonas syringae
Overview
- Primarily a disease of sweet cherry, tart cherries less susceptible
- Site, management, variety selection, and copper application are primary control strategies
Symptoms
- Cankers on trunk, limbs, and branches exude gum during spring and summer
- Leaves discolor and wilt on affected branches
- Leaf and fruit infection can occur when serious, as evidenced by necrotic spots, leaf yellowing, and/or water-soaked necrotic tissue on fruits
- Infected flower buds can fail to open in spring or result in rapid die-back browning of flowers/fruit/foliage
Disease cycle
- Bacteria over-winter on tree in canker margins, healthy buds, and in vascular system
- Bacteria multiply in spring and spreads during rainfall
- Wet, cool springs with frost or storms that damage blossom and leaf tissue favor outbreaks
- Bacteria can survive symptomless on leaves from bloom through leaf fall, whereupon infects fresh leaf scars and overwinters
Management
- Apply high rate copper in spring just before bud-break and in fall after leaf drop
- Avoid pruning in spring during wet weather; apply copper immediately after pruning
- Prune in summer after harvest
- Discard nursery stock at planting if any sign of bacterial canker present
More information
- Controlling bacterial canker of cherry. Fruit Notes, Vol. 79, Fall 2014
- Prune Cherries Immediately Following Harvest to Control Bacterial Canker. Fruit Notes, Vol. 72, Fall 2007
- December 2015 Presentation by Kari Peter BACTERIAL DISEASES OF STONE FRUITS: SPOTA AND CANKERS
bacterial canker shoot