Arborvitae: Leaf blight

categories: Arborvitae Arborvitae Diseases Conifers Ornamentals

revision date: 2023-02-07 12:00

Arborvitae leaves showing light tan areas of leaf blight with darker pitted areas.
Arborvitae Didymascella leaf blight
Photo by: R.S. Byther


Leaf blight is a fungal disease. The symptoms typically appear first in late spring as bleached spots followed by brown or black cushion-like fungal fruiting bodies. Infected foliage may be anywhere on the plant. Individual leaves are killed by the fungus and turn a light tan to gray color. As the fruiting bodies drop out of the leaves, deep pits are left in the dead tissue. The infected tissues often have a “scorched” appearance. Infected leaves often drop in the fall. Western red cedar (Thuja plicata) is most commonly infected, particularly the cultivars ‘Atrovirens’ and ‘Excelsa’. A similar disease attacks junipers.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

  • Plant resistant cultivars.
  • Avoid overhead watering. Leaf blight is favored by moist foliage conditions.
  • Space plants and prune to allow good air circulation.

Chemical Management

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

  • Make applications in spring and early summer.
  • 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.

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