Arborvitae: Berckmann’s blight
categories: Arborvitae Arborvitae Diseases Conifers Ornamentals
revision date: 2024-06-05 10:24
Photo by: R.S. Byther
Biology
Berckmann’s blight is a fungal disease of the leaves and small twigs of Oriental arborvitae. Growth at the tips of branches is infected first, turning brown in late spring. As the infection moves down the branch, foliage becomes grayish. Branchlets and twigs may be girdled and die back, with foliage above the dieback turning reddish-brown. Tiny black fruiting bodies of the fungus may be present on infected foliage and where twigs are girdled. Infected foliage drops from the plant. The fungus overwinters on infected tissues and can be spread by splashing water, insects, or air movement. Repeated severe defoliation will eventually kill plants.
Management Options
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- Berckmann’s arborvitae (Platycladus orientalis var. conspicua ‘Berckmannsii’) is especially susceptible. American and European arborvitae are not infected.
- Prune out and destroy infected branchlets and twigs.
- Avoid overhead watering.
- Provide proper culture. Arborvitae plants require good drainage and air circulation to remain healthy.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
Apply twice in fall, with the first application in late September or early October and the second application in early November. Apply again in early spring (February to March) if disease is severe. Do not use Lilly Miller Microcop Fungicide in spring. 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 Image
Photo by: R.S. Byther