Juniper: Phomopsis twig blight

Biology

Infection by Phomopsis begins with young leaves at the tips of shoots and can occur any time tender young foliage is available. Initially, small yellow spots appear on the scale-like leaves. As the infection spreads, leaves die and shoots fade to light green then reddish-brown and die back. The dead twigs remain attached. Gray to black fungal fruiting bodies develop at the base of or on killed portions. Phomopsis twig blight is spread by rain and splashing water. The disease is often worse in the center of the plant where branches join the trunk, making this disease easy to confuse with magnesium deficiency.

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 varieties such as Juniperus chinensis ‘Pfitzeriana Aurea’, ‘Iowa’, var. sargentii, var. sargentii ‘Glauca’, ‘Shoosmith’; J. communis var. depressa, ‘Repanda’; J. sabina ‘Arcadia’, ‘Broadmoor’, ‘Skandia’; J. scopulorum ‘Silver King’; J. virginiana ‘Tripartita’.
• Prune and destroy infected twigs.
• Avoid wounding plants.
• Avoid overhead watering. Keep plants as dry as possible and try to water only when foliage can dry quickly.
• Do not overfertilize.

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.
• 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 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