True Fir: Rust (Uredinopsis)

Biology

Uredinopsis rust is a fungal disease. Yellowish spots or blotches appear on the upper side of infected needles. A slight discoloration may first be observed on current-season needles in fall or winter. White, tube-like structures are typically found on the underside of last season’s needles in the spring and for one or more subsequent years. The white or colorless fungal spores are found inside these structures. Severely infected needles drop from the trees. All true firs can be infected by Uredinopsis rust. Brackenfern, the alternate host, shows discolored, yellowish markings on the upper side of fronds, and white fungal structures on the underside when infected. Rust diseases are favored by cool, moist springs. This disease is often confused with Pucciniastrum rust.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

• Remove alternate hosts within approximately 1,000 feet of susceptible trees.

Chemical Management

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

• If this disease has been a problem previously, make applications before symptoms are likely to develop.
• Ferti-lome Liquid Systemic Fungicide II R-T-Spray is labeled for use on Shasta fir only.
• 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.

• ferti-lome Liquid Systemic Fungicide II R-T-Spray
  Active ingredient: propiconazole [EPA registration number: 53883-184-7401]
• This list may not include all products registered for this use.

Additional Images