Arborvitae: Twig blight

Biology

Twig blight is a fungal disease of the leaves and shoots. Young leaves at the tips of shoots are infected first. This can occur any time tender young foliage is available. As the infection spreads down the shoots, leaves die and shoots turn dull red-brown. Branch tips are often girdled, with small gray lesions at the point of infection. Dead twigs turn gray and remain attached to the plant. Black fungal fruiting bodies develop on the girdling lesions. This disease is favored by moist conditions such as high humidity and damp foliage. The fungus can survive in killed tissues. This disease also infects 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!

• Thuja occidentalis ‘Ellwangeriana’ and ‘Lutescens’ are reported to be resistant.
• Avoid overhead watering.
• Prune out and destroy infected tissues.
• Space plantings to provide good air circulation.

Chemical Management

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

• Apply at 2-week intervals in spring, beginning when growth starts.
• Additional applications may be needed after pruning or shearing.
• 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.

• Bonide Copper Fungicide Spray or Dust RTU [Organic]
  Active ingredient: basic copper sulfate [EPA registration number: 4-58]
• Monterey Liqui-Cop Copper Fungicidal Garden Spray
  Active ingredient: copper-ammonia complex [EPA registration number: 54705-7]
• Soap-Shield Flowable Liquid Copper Fungicide [Organic]
  Active ingredient: copper octanoate [EPA registration number: 67702-2-56872]
• Bonide Infuse Systemic Disease Control Lawn and Landscape
  Active ingredient: thiophanate methyl [EPA registration number: 53883-183-4]
• This list may not include all products registered for this use.

Additional Images