Rust fungus (Puccinia monoica) on plants located close to the Truckee River near Squaw Valley, CA. Mar. 17, 2015. Photo: Joanna Rutkowski.
Puccinia monoica is a type of rust fungus that usually infects plants of the Arabis genus of the Mustard Family (Brassicaceae). Plants become infected with spores of the rust fungus during the late summer. During the following spring, the infected plants sprout flower-like clusters of bright yellow leaves, which look completely different from the host plant’s normal flowers and are coated in a sticky, sweet-smelling substance (Roy 1993). This is an example of floral mimicry: Fungi masquerading as flowers.
In spring, as insects go from flower to flower looking for pollen, they may instead be lured in by the bright colors and fragrant odors of a rust fungus. Frequent visitors to rust fungus include bees, butterflies and flies. The rust fungus uses these insects to transport its spermatia (reproductive cells) from plant to plant (Roy 1993) — a fascinating (and slightly creepy) reproductive strategy.