Western gall rust

Western gall rust - Branch and stem galls on lodgepole pine caused by <em>E. harknessii</em>
  • Latin name: Endocronartium harknessii (J.P. Moore) Y. Hiratsuka
  • French name: Rouille-tumeur autonome
  • Division: Basidiomycota
  • Class: Uredinales
  • Synonym(s): Cronartium harknessii E. Meinecke,
    Peridium cerebroides E. Meinecke,
    Peridium harknessii J.P. Moore


Twig, Branch



Damage, symptoms and biology

The fungus causes a gall that encircles the stem or bole of infected trees. White blisters develop at the site of the gall, just beneath the bark. In spring, the blisters burst and orange spores are released which end up infecting other pines. Rupturing of the blisters results in desiccation of the underlying living bark, killing the bark area around the gall. Following the death of the water-conducting tissues, some needles will die in the lower part of the branch, near the distal portion of the gall.

Damage is not significant on mature trees where most infections occur on branches. Branch galls do not result in serious growth losses. However, infections on young trees more often result in main stem galls that can cause stem malformations and predispose the tree to breakage in high winds or under heavy snow loads (Figs e, f).

A large numbers of galls reduces the aesthetic appearance and value of ornamentals and Christmas trees.

Other information

Unlike the other important stem rusts, E. harknessii does not require an alternate host to complete its life cycle. Infection occurs directly from pine-to-pine. This allows rapid intensification of the disease when conditions optimal for infection occur. However, such conditions only occur every several years, resulting in "wave years" of infection and gall formation.

Pruning the infected branches prior to spore production is a good means of control. Rodents feed on the galls in winter, and this may result in a high level of mortality some years.

Canadian Forest Service Publications

Western gall rust

Information on host(s)

Main host(s)

Jack pine, Monterey pine, scots pine, scots pine, shore pine

Secondary host(s)

Austrian pine, mugho pine

  • Western gall rust Galls on a branch
  • Western gall rust Galls on a branch
  • Western gall rust Tree infected by the western gall rust
  • Western gall rust Galls on branches
  • Western gall rust Branch and stem galls on lodgepole pine caused by E. harknessii
  • Western gall rust Stem breakage at the site of a western gall rust gall
  • Western gall rust EndoCronartium harknessii gall with orange spores produced beneath bark
  • Western gall rust Immature gall that has never produced spores on one-year-old pine branch
  • Western gall rust Main stem galls on nursery-produced pine seedlings
  • Western gall rust A jack pine heavily infected with globose galls caused by Endocronartium harknessii, the causal agent of western gall rust.
  • Western gall rust Fruiting of Endocronartium harknessii, the cause of western gall rust, on a jack pine.
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