Rhabdocline spp.

Photo by Ralph Byther, Washington State University.

Signs & Symptoms

Photo by Kathy Riley, Washington State University.

Before bud break:

  • Reddish-brown spots on upper surface of current-year needles; distinct border between diseased area and healthy green tissue
  • Swollen, elongated, light-tan fruiting bodies on the underside of symptomatic needles

During bud break:

  • Fruiting bodies rupture underside of needle, releasing a mass of spores.

Where to Look

Photo by Chal Landgren, OSU.

  • Douglas-fir sources from east of the Cascades

Similar Symptoms As

Photo by Ralph Byther, Washington State University.

  • Cooley spruce gall adelgid
  • Swiss needle cast
  • Douglas-fir needle midge
  • Rust


  • Search for symptoms prior to bud break, in late winter or very early spring.
  • Look for reddish-brown splotches on the upper needle surface. Only the newly emerging spring growth can become infected.

Management Options

  • At bud break, spray fungicide (if needed) to prevent infection.
  • Remove and destroy severely infected trees prior to bud break.
  • Plant resistant or tolerant tree varieties; avoid Douglas-fir from Rocky Mountain seed sources, unless tested.

Host Susceptibility

host susceptibility graph

  • High susceptibility: Douglas-fir only

Management Calendar

management calendar

  • Look for current needles with reddish-brown spots: Mid-February through Mid-June
  • Check underside of needles for fruiting bodies: Mid-February through Mid-April
  • Use fungicides to protect emerging needles: Mid-April through June