White Pine Blister Rust

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White Pine Blister Rust

Scientific Name
Cronartium ribicola
White Pine Blister Rust
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Hero Nate

White pine blister rust is a fungus that greatly affects the branches and trunks of white pine trees. 

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White Pine Blister Rust
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White Pine Blister Rust
Clues That The Fungus is Nearby I

Close-up of the bottom side of a currant leaf infected with white pine blister rust. The hair-like, orange structures in the picture release spores of the fungus , which can infect white pines.

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When white pine blister rust infects a pine branch, it often kills the phloem all the way around it, causing the needles to turn brown and the branch to die.

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A currant (Ribes spp.) leaf carrying the white pine blister rust fungus appears to be covered in rust! 

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Symbiosis! Why we better save whitebark pines from blister rust
Clues That The Fungus is Nearby II

The blisters caused by white pine blister rust break through the tree’s bark when the fungus is ready to reproduce. The yellow parts in the blisters are the spores .

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Pine branches infected with white pine blister rust often become fatter, or swollen, where the fungus is causing damage. The “blisters” caused by this fungus can also be seen here.

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Host Plants

Cones , seeds, and leaves of eastern white pine, the only species of pine in the eastern U.S. that suffers from white pine blister rust. These trees can easily be identified because they hold their needles in groups of five. 

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Western white pines are majestic trees that were once very important for timber. Almost 90% of them outside of California have been killed by white pine blister rust.

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Close-up of the cones and short needles of Pinus flexilis. The common name is “limber pine” because the branches are so flexible they can be tied in knots! Unfortunately, this tree is very susceptible to white pine blister rot.

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Alternate Hosts

Alternate hosts are secondary host plants that a disease needs to complete its lifecycle. If an alternate host is not available, the disease will die out. These flowers might look pretty, but louseworts (Pedicularis spp.) were recently discovered to be alternate hosts for the white pine blister rust fungus !

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Indian paintbrush (Castilleja sp), a small flowering plant native to the U.S., was recently discovered to be an alternate host for the white pine blister rust fungus

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Gooseberry Currant

Leaves of a gooseberry currant (Ribes montigenum), an alternate host of white pine blister rust. The fungus requires this plant or another alternate host to complete its lifecycle, but on Ribes it only infects the leaves, which does not harm the plant very much.

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Gooseberry currants (Ribes montigenum), alternate hosts of white pine blister rust, are small to medium shrubs with red or purplish fruit.

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Damage

An eastern white pine infected with white pine blister rust. Dead or yellowing tops are common on infected trees because the pathogen can cut off water and nutrients to the portion of the tree above the infection site.

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Many of these pines have been affected by white pine blister rust . The reddish-brown, dead needles caused by this disease can be seen here.

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White pine blister rust has affected most of the pines on this hillside.

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Impact

Whitebark pine (Pinus albicaulis) is a very important species in the high mountains of the Western U.S. It may not be very abundant, but many animals and plants depend on it for survival. This species is highly threatened by white pine blister rust and mountain pine beetle.

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Pine trees are very important parts of their ecosystems. They provide food for many different animals, including red squirrels like this one.

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A Valuable Food Source

In the high mountains of the Western U.S., nutritious pine seeds are a very important food for grizzly bears. If white pine blister rust affects all the pine trees, what will the grizzlies eat?!

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This is a Clark’s nutcracker (Nucifraga columbiana). They depend on seeds from the whitebark pine to survive, and bury large seed stashes in the ground! The pines depend on this special bird to plant their seeds so new trees can grow. Both whitebark pine trees and Clark’s nutcrackers are in danger because of white pine blister rust.

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Hero Nate

Do you think you've found evidence of white pine blister rust? Click the "learn more" button below to read about the disease and to get in touch with the experts. 

White pine blister rust: USDA Forest Service, Northern and Intermountain Region , USDA Forest Service, Bugwood.org.; Leaf: Robert L. Anderson, USDA Forest Service, Bugwood.org.; Canker with fungus : US Forest Service, Odgen, Bugwood.org.; Currant leaf: Joseph O'Brien, USDA Forest Service, Bugwood.org.; Infected leaf: Jari Poutanen, Flickr.com.; White pine damage: Joseph O'Brien, USDA Forest Service, Bugwood.org.; Diagram: Steven Katovich, USDA Forest Service, Bugwood.org.; Blisters: Joseph OBrien, USDA Forest Service, Bugwood.org.; Pine diagram: Zelimir Borzan, University of Zagreb, Bugwood.org.; White pines: Wikimedia Commons.; Limber pine cones , Gooseberry currant: Dave Powell, USDA Forest Service (retired), Bugwood.org.; Louseworts: Mary Ellen (Mel) Harte, Bugwood.org.; Indian paintbrush: OakleyOriginals, Flickr.com.; Damaged forest: State & Private Forestry, Forest Health Protection, Flickr.com.;  Hillside pines: USDA Forest Service - Ogden , USDA Forest Service, Bugwood.org.; Whitebark pine: Dave Powell, USDA Forest Service (retired), Bugwood.org.; Squirrel, bear: Terry L Spivey, Terry Spivey Photography, Bugwood.org.; Clark's nutcracker: Vern Wilkins, Indiana University, Bugwood.org.

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