Puccinia monoica (Rust Fungus) - photos and description
Uninfected plant (foliage all grey) on the left of the photo.
General: Parasitic rust fungus that infects prairie
plants in early spring, usually species of Rock Cress (Boechera/Arabis). The
fungus transforms the host plant to produce the sexual structures
of the fungus.
I've been asked to identify this 'plant' a few times. People
don't recognize it as a Rock Cress and perhaps are
confused because of the bright yellow pseudoflowers the plants produce
due to the fungus.
Flowers: The infected plant produces clusters of leaves resembling bright yellow pseudoflowers, mimicking the inflorescence of spring-flowering Buttercups. Both sides of the leaves and upper stems are covered in spermagonia. The pseudoflowers produce a pungent fragrance and exude a sugar-rich solution to attract pollinators to spread the fungus.
Leaves: Varies by the species of Rock Cress.
Height: We measured stems to 15 cm.
Habitat: Prairies.
Abundance: Fairly common / uncommon.
Origin: Native.
When and where photographed: Took the above photos on April 12th, prairie hillside, Buffalo Pound provincial park, about 65 km west of our home in Regina, SK.