A fourth hard pine stem rust, sweet fern blister rust only infects very young seedlings in close proximity to its alternate host (which is relatively uncommon and restricted to wetlands). The overall infection risk to pine by sweet fern blister rust is quite low and therefore has not been detailed here.

These hard pine stem rusts, so called because they infect hard pine, lodgepole and/or ponderosa pine, can cause significant damage in young plantations or natural stands and as a result must be a consideration when contemplating density management investments.

STALACTIFORM BLISTER RUST
Cronartium coleosporioides(Arthur)
Hosts:

• Tree host (aecial) - lodgepole pine, ponderosa pine
• Alternate host (telial) - paintbrush, cow-wheat (yellow owlπs clover, bracted lousewort and yellow rattle)

What to look for:
Stalactiform blister rust forms elongate, perennial cankers on stems and branches.  Blisters form in the late spring and early summer releasing white-orange spores.  The visible nature of the spores makes detection much simpler and more accurate.

• Areas known to have a high stalactiform blister rust hazard should be surveyed during the sporulation window to improve the accuracy of rust incidence data.
• Identifying the presence of the alternate host may help in assessing risk.
• Stalactiform blister rust can be confused with comandra blister rust but stalactiform has more elongate cankers.

Damage
Girdling of small stems can result in mortality.  Defects created on larger stems can weaken the wood, often resulting in stem damage or breakage from wind, snow or ice.

Credit: PFC FHN CFS	Credit: NE Alexander	Credit: NE Alexander

COMANDRA BLISTER RUST
Cronartium comandrae (Peck)
Hosts:

• Tree host (aecial) - lodgepole pine, ponderosa pine
• Alternate host (telial) - California Comandra or Bastard toadflax.

What to look for:
Comandra blister rust causes swelling and cracking of the bark on stems and branches (some resinosis may also be present). Perennial cankers form producing orange spores in the spring and early summer.  The visible nature of the spores makes detection much simpler and more accurate.

• Areas known to have a high comandra blister rust hazard should be surveyed during the sporulation window to improve the accuracy of rust incidence data.
• Identifying the presence of the alternate host may help in assessing risk.
• Comandra blister can be confused with stalactiform blister rust.
• Porcupine and other rodents often gnaw on the cankers exposing the wood underneath.
  

Damage:
Stem defects and mortality can result from girdling of stems and branches caused by the growth and expansion of the cankers.

Credit: PFC FHN CFS	Credit: E.Allen CFS	Credit: NE Alexander

WESTERN GALL RUST
Endrocronartium harknessii (J.P. Moore) Y Hiratsuka
Hosts:

• Tree host - lodgepole pine, ponderosa pine
  

What to look for:
Western gall rust causes the formation of woody swellings, galls on stems and branches (some resinosis may also be present). These galls will grow as the tree grows and will produce orange spores from beneath the bark in the late spring.  The visible nature of the spores makes detection much simpler and more accurate.

• Areas known to have a high western gall rust hazard should be surveyed during the sporulation window to improve the accuracy of rust incidence data.
  

Damage:
Galls occurring on the main stem of young trees may weaken the wood resulting in stem breakage from wind, snow or ice.

Credit: PFC FHN CFS	Credit: NE Alexander	Credit: PFC FHN CFS

References
Alan, E., D. Morrison and G. Wallis.1996. Common Tree Diseases of British Columbia. Can. For. Serv.
Finck, K, P. Humphreys, G. Hawkins. Field Guide To Pests of Managed Forests in British Columbia. FRDA – Joint publication, ISSN 0843-4719, no. 16.