Huckleberry (Vaccinium spp.)-Witches' Broom Rust

See:

Cause Pucciniastrum goeppertianum, a rust fungus that alternates between Vaccinium spp. (huckleberry, blueberry, and cranberry) and true firs. Infection of huckleberry leads to extensive growth in the phloem each year. The telia encircle the swollen stems and produce teliospores that germinate in the spring. Teliospores produce basidiospores, which are dispersed during rain storms. These spores will infect grand, silver, balsam, and subalpine firs. Aecia produced on the fir needles shed aeciospores that infect huckleberry. A uredinial state has not been found. Cool, moist springs favor disease development. Although easily found in natural settings, it is not considered an economic or ecological problem.

Symptoms Evergreen huckleberry (Vaccinium ovatum) develops a witches' broom of thickened stems with few or no leaves. Telia form in a reddish brown layer around stems each year. Branches are swollen, spongy, and distinctly yellowish to reddish brown in contrast to the greenish color of normal twigs.

Firs develop white tube-like fruiting structures (aecia) on the lower needle surface. Aecia of can mature on current-year needles in late summer or on previous year's needles in early summer. Aeciospores are generally yellow. Severe infections result in needle drop.

Cultural control

  • Remove the alternate host for at least 1000 ft around plantations.
  • Removal of the affected branches will have little affect beyond aesthetics.

Chemical control No chemicals are specifically registered for this disease on huckleberry; however, the following may be effective.

  • Proline 480 SC at 5.7 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
  • Propulse at 13.6 fl oz/A. Do not use within 7 days of harvest. Group 3 + 7 fungicide. 12-hr reentry.
  • QuiltXcel at 14 to 21 fl oz/A. Do not use within 30 days of harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
  • Tilt at 6 fl oz/A. Do not use within 30 days of harvest. 12-hr reentry.

Reference Ziller, W.G. 1974. The Tree Rusts of Western Canada. Canadian Forestry Service Publication 1329.