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Bacterial blight (Leaf spot)

Pseudomonas syringae pv. viburni or Xanthomonas spp.

30 host plants

Last updated

Data Coverage 3 of 6 dimensions
Causal Agent
Host Plants
Symptoms
Management
GDD Threshold
Regional Notes

Leaves show dark lesions with water-soaked margins while shoots may develop expanding cankers. This bacterial disease spreads by rain splash. Improve air circulation and disinfect tools.

Remove blighted tissue promptly, cutting well below visible symptoms. Improve air circulation by thinning dense growth. Avoid overhead watering, especially during bloom and new growth periods when tissues are most susceptible. For recurring problems, preventive fungicide applications timed to protect new growth can reduce infection, but cultural controls should be your first approach.

Quick Reference

Causal Agent
Pseudomonas syringae pv. viburni or Xanthomonas spp.
Host Plants
30
Favorable Conditions
Cool temperatures; high humidity; rain or overhead irrigation; crowded planti...

Management

Vulnerability Window

Apply fungicides in September and again before fall rains.

What Triggers Infection

Cool temperatures; high humidity; rain or overhead irrigation; crowded plantings with poor air circulation

Cultural Controls

  • Plant resistant viburnums such as Viburnum burkwoodii 'Mohawk', V.
  • carlcephalum 'Cayuga', V.
  • lantana 'Mohican', or V.
  • rhytidophyllum 'Alleghany'.
  • Plant in full sun.
  • Space plants and prune to provide good air circulation.

Host Plants (30)