Huckleberry Broom Rust
Pucciniastrum goeppertianum (Kühn) Kleb.
Hosts in Alaska:
Vaccinium spp., especially red huckleberry V. parvifolium (telial lifecycle stage)
Abies spp. (aecial lifecycle stage)
Damage: dense clustered branching (brooms) on Vaccinium spp., foliage infection on Abies spp.
Each year, we receive between one and five enquiries about the cause of strange branching on red huckleberry (Vaccinium parviflorium) in Southeast Alaska. The incidence of this native, perennial broom rust is not expected to change significantly from year to year, but infection conditions may be especially favorable in certain years. Reports have been made near Ketchikan, Sitka, San Fernando Island (west of Prince of Wales Island), and western Admiralty Island south of Angoon. Interestingly, this fungus has lifecycle stages on needles of true firs (Abies spp.), which have limited distributions in Southeast Alaska.
Sometimes huckleberry broom rust is confused with another disease of blueberry stems caused by the pathogen Exobasidion parviflorii, which causes canker-gall spots and elongated fruiting structures on Vaccinium stems, especially V. parvifolium. While P. goeppertianum produces fruiting structures on the branch tissue of the host, E. parviflorii produces noodle-like fungal fruiting structures that emerge from stem cankers, resembling club fungi in the genus Clavaria. E. parviflorii tends to be fleshy whitish to pale green to pink, and becomes blackened and dried (called shoestring galls) with time.
Symptoms, Lifecycle & Impacts
The aecial stage on firs is produced on current year’s needles in late-summer, or maturing on previous year’s needles in early summer. Needle infection causes discoloration of current and/or previous year’s fir needles. The telial stage on Vaccinium spp. is most prevalent on red huckleberry (V. parviflorum) in Alaska, causing perennial brooms (dense branching) comprised of reddish brown swollen twigs that lack leaves or have stunted leaf development. Disease on huckleberry often occurs far from firs, raising questions about whether the disease can cycle on Vaccinium spp. alone; however, experiments have not been conducted to test this. This rust rarely causes heavy damage to its hosts. This disease has only been observed on red huckleberry in Alaska.
Disease Cycle Diagram
Links & Resources
Ziller, W.G. 1974. The Tree Rusts of Western Canada. Canadian Forestry Service Publication 1329.
Huckleberry (Vaccinium spp.)- Witches Broom. Oregon State University Extension Service Pacific Northwest Plant Disease Handbook.
Content prepared by Robin Mulvey, Forest Pathologist, Forest Health Protection, email@example.com.