white pine blister rust
(Cronartium ribicola)
This species is Introduced in the United States
Origin
White Pine Blister Rust (WPBR), caused by the fungus Cronartium ribicola, is one of the most important diseases of white pines (Pinus sect. Quinquefolius). White pines, especially young trees, and plants belonging to the genus Ribes (currants and gooseberries) are susceptible to the disease. The fungus is native to Europe and Asia, and white pines native to Europe and Asia are generally resistant to the disease, while those native to North America are more susceptible.
Life Cycle
During moist weather in August and early September, after seasonally cool weather has prevailed for about 2 weeks, telia on leaves of Ribes plants produce spores that cause new infections on pine needles. The rust fungus grows slowly within the pine needle and twig; aecia (blisters) first rupture the bark in April-May of the second or third growing season after a pine needle becomes infected. The spores from these blisters (aeciospores) cause new infections on the growing leaves of Ribes plants but are not capable of causing infections on pine. This alternation of host plants is essential for the perpetuation of the fungus; it cannot complete its life cycle on the pine or Ribes alone.
The pimple-like uredinia that develop on infected Ribes leave produce orange spores (urediniospores) that cause new infections on Ribes leaves throughout the growing season. These spores, however, are not capable of causing infections on pines. The telia that develop on infected Ribes leaves in late summer produce spores (called basidiospores) that cause new infections on pines. The infected pines provide a place where the rust fungus may safely overwinter; it cannot survive in the Ribes leaves or outside a living host plant.
Distribution
The fungus occurs throughout Europe and Asia at low levels wherever white pines occur, causing little damage to the species which have evolved alongside it. It was introduced accidentally to eastern North America early in the 20th Century and soon spread across the range of Eastern White Pine, causing extensive mortality. By the 1930s it had appeared in the Pacific Northwest, introduced accidentally on Eastern White Pine nursery stock. Resulting mortality in Western White Pine, Sugar Pine, and Whitebark Pine has been even higher than in Eastern White Pine, though the spread of the fungus into southern California has been slowed by the hot dry summer climate there. Spread is continuing south into Arizona and New Mexico, causing high mortality on Southwestern White Pine.
Control Efforts
Branches with cankers should be cut off where they join the next healthy branch. This cut should be made at least 5.9″ (15 cm) beyond the yellowish margin of the canker. This margin can be easily detected by rubbing the area with a wet cloth. Lower branches are most commonly infected. If lower branches are removed, the probability of infection is reduced. Infections on trunks can be eliminated by removing all bark 2″ (5 cm) on each side and 3.9″ (10 cm) above and below the canker margin. After excision of the infected bark or removal of a branch, the area may be treated with a tree wound dressing for cosmetic purposes.
The current cultivars 'Cornet', 'Consort', and 'Crusader' are resistant to white pine blister rust. In one study, the cultivars 'Red Lake', 'Jumbo', 'Cherry', and 'White Current' were less susceptible and the cultivars 'Welcome', 'Redjacket', 'Green Hansa', 'Poorman' and 'Pixwell' were the most susceptible.
White Pine Blister Rust (WPBR), caused by the fungus Cronartium ribicola, is one of the most important diseases of white pines (Pinus sect. Quinquefolius). White pines, especially young trees, and plants belonging to the genus Ribes (currants and gooseberries) are susceptible to the disease. The fungus is native to Europe and Asia, and white pines native to Europe and Asia are generally resistant to the disease, while those native to North America are more susceptible.
Life Cycle
During moist weather in August and early September, after seasonally cool weather has prevailed for about 2 weeks, telia on leaves of Ribes plants produce spores that cause new infections on pine needles. The rust fungus grows slowly within the pine needle and twig; aecia (blisters) first rupture the bark in April-May of the second or third growing season after a pine needle becomes infected. The spores from these blisters (aeciospores) cause new infections on the growing leaves of Ribes plants but are not capable of causing infections on pine. This alternation of host plants is essential for the perpetuation of the fungus; it cannot complete its life cycle on the pine or Ribes alone.
The pimple-like uredinia that develop on infected Ribes leave produce orange spores (urediniospores) that cause new infections on Ribes leaves throughout the growing season. These spores, however, are not capable of causing infections on pines. The telia that develop on infected Ribes leaves in late summer produce spores (called basidiospores) that cause new infections on pines. The infected pines provide a place where the rust fungus may safely overwinter; it cannot survive in the Ribes leaves or outside a living host plant.
Distribution
The fungus occurs throughout Europe and Asia at low levels wherever white pines occur, causing little damage to the species which have evolved alongside it. It was introduced accidentally to eastern North America early in the 20th Century and soon spread across the range of Eastern White Pine, causing extensive mortality. By the 1930s it had appeared in the Pacific Northwest, introduced accidentally on Eastern White Pine nursery stock. Resulting mortality in Western White Pine, Sugar Pine, and Whitebark Pine has been even higher than in Eastern White Pine, though the spread of the fungus into southern California has been slowed by the hot dry summer climate there. Spread is continuing south into Arizona and New Mexico, causing high mortality on Southwestern White Pine.
Control Efforts
Branches with cankers should be cut off where they join the next healthy branch. This cut should be made at least 5.9″ (15 cm) beyond the yellowish margin of the canker. This margin can be easily detected by rubbing the area with a wet cloth. Lower branches are most commonly infected. If lower branches are removed, the probability of infection is reduced. Infections on trunks can be eliminated by removing all bark 2″ (5 cm) on each side and 3.9″ (10 cm) above and below the canker margin. After excision of the infected bark or removal of a branch, the area may be treated with a tree wound dressing for cosmetic purposes.
The current cultivars 'Cornet', 'Consort', and 'Crusader' are resistant to white pine blister rust. In one study, the cultivars 'Red Lake', 'Jumbo', 'Cherry', and 'White Current' were less susceptible and the cultivars 'Welcome', 'Redjacket', 'Green Hansa', 'Poorman' and 'Pixwell' were the most susceptible.
Resources
- Misc. Forest Service Publication - USDA Forest Service
- How to Manage Eastern White Pine to Minimize Damage from Blister Rust and White Pine Weevil - USDA Forest Service
- How to Identify White Pine Blister Rust and Remove Cankers - USDA Forest Service
- Global Invasive Species Database - Invasive Species Specialist Group
Selected Images
Invasive Listing Sources
- Idaho Invasive Species Act
- Maryland Invasive Species Council - Invasive Species of Concern in Maryland
- New Jersey Invasive Species Strike Team 2017 Invasive Species List
- Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
- South Carolina Plant Pest List
- West Virginia Invasive Species Strategic Plan and Volunteer Guidelines 2014
Taxonomic Rank
| Domain: Eukarya |
| Kingdom: Fungi |
| Phylum: Basidiomycota |
| Subphylum: Pucciniomycotina |
| Class: Pucciniomycetes |
| Order: Pucciniales |
| Family: Cronartiaceae |
| Genus: Cronartium |
| Cronartium ribicola |
References
Common Name Reference: Hansen, E.M. and K.J. Lewis. 1997. Compendium of Conifer Diseases. APS Press. 3340 Pilot Knob Road, St. Paul, MN 55121-2097. 101 pp.
Scientific Name Reference: Index Fungorum. Paul Kirk. CABI, CBS and Landcare Research. http://www.indexfungorum.org/