Bacterial Blights
Pseudomonas syringae
0 host plants
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
General leaf spotting and twig dieback occur from various bacterial pathogens. Remove affected material, improve sanitation, and avoid overhead watering.
Maintain adequate spacing between plants and prune to provide good air circulation within the canopy. Prune out and burn all affected tissues immediately.
Quick Reference
Management
Late fall through early spring, when cool wet conditions persist. Young shoots in early spring are most susceptible as they develop. Flower clusters are vulnerable from bud break through bloom. Frost-damaged tissues provide entry points during dormancy. Plants weakened by improper nutrition, wounds, or other pathogens are at increased risk." # Source: PNW Plant Disease Management Handbook (Lilac - Bacterial Blights)
Cool temperatures (below 65°F/18°C) with persistent moisture from rain or overhead irrigation. Frost events are critical — P. syringae produces ice nucleation active (INA) proteins that promote frost damage at 28-25°F, creating wounds for bacterial entry. Mild, moist weather from fall through early spring favors disease development. High humidity and poor air circulation increase infection risk." # Source: PNW Plant Disease Management Handbook (Lilac - Bacterial Blights)
Cultural Controls
- Maintain adequate spacing between plants and prune to provide good air circulation within the canopy.
- Prune out and burn all affected tissues immediately.
- Plant resistant species or cultivars.
- Do not fertilize late in the growing season.
- Do not over-fertilize young plants.
- In spring, protect from rain and frost with plastic hoop houses or similar structures. Plastic structures reduce disease by preventing rain splash and frost exposure." # Source: PNW Plant Disease Management Handbook