[5] The most prominent symptoms are hip cankers and swollen, spherical to oblong growths (galls) on the branches, stems, or main trunk of the host.

Western gall rust can cause dwarfing to occur if leader stem of younger pines are infected.

Early identification of the disease is important for treatment, but is often hard to diagnose due to the inconspicuous initial symptoms and a lack of galls until the second year.

A red pigmentation may develop on the epidermal galls of P. contorta seedlings 14–28 days after infection, but this is not always a reliable indicator.

Gall formation on trunks occurs over 2–4 years and is stimulated by the pathogen, which causes cells to grow and divide quickly at the site of initial infection.

[citation needed] Wind carries teliospores to pines shoots that then germinate under cool humid conditions, producing germ tubes with up to three side branches that act as basidia.

Haustoria extend through neighboring cells and the cortex to reach the vascular cambium before the host becomes dormant follow the first infection season.

The host reacts by hyperplasia (increased division) providing the resources needed for further hyphae proliferation in the cortex, phloem, and cambium until the galls death.

Dikaryotization of the haploid mycelium that produce the teliospores takes place in the outer cortex, just beneath the first periderm.

Environmental conditions conducive to infection typically occur during spring and early summer when weather is consistently cool and moist.

2135-32) registered in California can help control western gall rust, although it is not used on seeds or seedlings and may kill mycorrhizal fungi if advised application concentration is exceeded.

[14] Although pruning infected stems from the tree may lower the initial inoculum, it provided little benefit to lesioned branches as they often die.

Some feed on the aeciospores and can negatively impact the fungus’ survival while other insects, like the red turpentine beetle, can carry spores to other trees.

Pine-pine gall rust is economically significant because of its detrimental effects on lumber content, quality, and growth rate.

Pine-pine gall rust is also an important disease for nursery owners growing pines to look out for because young trees and seedlings are particularly susceptible.

Severe outbreaks in natural stands and plantations of Pinus contorta, P. ponderosa, P. banksiana, and P. sylvestris have been observed in regions of Canada.

The disease is also significant due to its negative impact on the aesthetic quality of specimen trees in public gardens, arboretums, and residential areas.

[7] True epidemics of pine-pine gall rust are rare, occurring only in years when susceptible hosts, virulent pathogens, and proper environmental conditions are present simultaneously.