WSU Extension

Hortsense

Caption: Fir Uredinopsis rust
Photo by: R.S. Byther
  
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True Fir : Rust (Uredinopsis)
(revision date: 4/23/2014)


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

Non-Chemical Management
  • Remove alternate hosts within approximately 1,000 feet of susceptible trees.
Select non-chemical management options as your first choice!

Chemical Management


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.

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 reg no: 53883-184-7401
  • This list may not include all products registered for this use.
Images
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Caption: Fir Uredinopsis rust
Photo by: R.S. Byther
Caption: Uredinopsis rust on bracken fern, upper surface
Photo by: R.S. Byther
Caption: Uredinopsis rust on bracken fern, lower surface
Photo by: R.S. Byther