Lilac: Bacterial blight

categories: Lilac Lilac Diseases Ornamentals Shrubs

revision date: 2024-06-05 10:24

Lilac bacterial blight showing on new growth.
Lilac bacterial blight (1)
Photo by: J.R. Glass


Bacterial blight starts as brown spots on leaves and stems in the early spring. These spots become black with age and cause death of leaves and young shoots, which may bend over at the infection site. Infected older shoots show dying leaves as the infection enlarges along the stem. Flower clusters may also be affected. Infection often occurs on weakened or unhealthy plants and at injury sites such as those caused by wounds and frost damage. Pears, blueberries, cherry, maple, and many other woody plants can also be infected by this blight.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • Maintain proper plant nutrition. Healthy plants resist disease better.
  • Avoid overhead irrigation.
  • Space plants properly and prune to provide good air circulation. This will slow down spread of the disease.
  • Avoid injuring plants to reduce possibility of infection.
  • Prune and destroy infected tissues as soon as they are noticed.
  • Plant disease-resistant species such as Syringa perkinensis, S. microphylla, or S. vulgaris vars. ‘Alphonse Lavallec’, ‘Crepuscule’, ‘Floreal’, ‘Guinevere’, ‘Jeanne d’Art’, ‘Lutece’, ‘Maud Notcutt’, ‘Mrs. W.W. Marshall’, ‘Rutilant’, or ‘William Robinson’.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • Apply before fall rains and again before budbreak in spring.
  • Do not use Lilly Miller Kop-R-Spray Concentrate for spring applications.
  • Homeowners should not make foliar applications to trees over 10 ft tall.
  • Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Additional Images