Ascochyta Blight

  • Symptoms

    • In the Spring, the current year's shoots and flower stalks are girdled, wilted, and brown. The base of the dead area is tan to gray and shriveled. In wet weather, dark gray pimple-like fungal fruiting structures dot the dead tissue. In Summer and Autumn, olive green round leaf spots turn tan and have indefinite edges. Fungal fruiting structures dot the upper surface of the spots.
  • Management

    • Prune infected tissue. Avoid overhead irrigation. Apply mancozeb, or chlorothalonil to protect healthy shoots.

Bacterial Blight

  • Symptoms

    • Leaves turn completely brown to black and remain attached to the branch. Shoots are girdled and killed. Flower buds are blackened while flower clusters become limp and brown. See shoot blight below.
  • Management

    • Prune infected branches, cutting well below the diseased tissue. Disinfest the pruning shears between cuts. Apply mancozeb + copper to protect new growth.

Bacterial Blight on Lilac


Powdery Mildew

  • Symptoms

    • Dry white fungal growth develops on the surface of leaves. Leaves become distorted.

Powdery Mildew on Lilac


Shoot Blight

  • Symptoms

    • Shoots are killed extensively, up to 4 to 5 feet, and turn very black. Root sprouts at the base of the plant are killed and blackened.
  • Management

    • Remove the infected plant; do not replace it with plants susceptible to Phytophthora. Avoid overhead watering of healthy plants.

Shoot Blight affecting Lilac


Witches' Broom

  • Symptoms

    • Short, thin twigs and branches originating from one area of the stem form dense clusters. Leaves may be distorted, small, and yellow. Twigs forming the brooms are abnormally upright and often retain green leaves too long in the autumn and die back in Winter.
  • Management

    • Prune infected branches. Remove severely infected plants.

Lilac Witches' Broom