Taisha wrote this entry:
Today's image is of the rust Puccinia monoica (Pucciniaceae) growing on a host plant, Smelowskia calycina (Brassicaceae). It was taken by Anne Elliott (aka annkelliott@Flickr), a regular contributor to the Botany Photo of the Day Flickr Pool. Thanks Anne! Doug Waylett also has photographs of Puccinia monoica on Flickr, including these: photo 1 and photo 2.
Puccinia monoica is macrocyclic (producing 5 different kinds of spores during its life cycle: pycniospores, aeciospores, urediniospores, teliospores and basidiospores). The species is also heteroecious, meaning it requires two unrelated hosts to complete its life cycle. For Puccinia monoica, the aeicial stage host is from the Brassicaceae, while the telial host is from the Poaceae.
I decided to write about a rust fungus, particularly one from the genus Puccinia, as I recently submitted a research proposal for my weed science class (I mentioned this class in the post on Fallopia convolvulus), where I'm looking into the potential of using a specific rust fungus from the genus Puccinia as a biological control agent to suppress a weedy Caryophyllaceae species that is common both in Canada and globally. Despite some Puccinia species being used for weed control, I haven't come across any references that indicate Puccinia monoica is among them.
Biological control of weeds is when one uses a living organism to manage problematic plants. In some cases, pathogens like fungi are used. Fungal pathogens can affect their host plant's ability to compete for limited resources, reduce the growth rate of the host and/or increase susceptibility to other pests. Rust fungi have the ability to spread rapidly over large areas, are destructive, and are host specific, making them ideal candidates for use as a biological control agent against weeds. Fungi as a biocontrol agent are either used in an inoculative (classical) approach, or an inundative (mycoherbicidal) approach. The inoculative approach is a low-cost one that involves introduction of an exotic pathogen to manage a weed population over a long period of time. The inundative technique is a higher-cost method where a weed population is overwhelmed with a direct application once or many times, similar to herbicide. The pathogen in this method is often called a bioherbicide, and, if it happens to be a fungus, usually referred to as a mycoherbicide.
If you're interested in learning more you can look into Fungi as a Biocontrol Agent: Progress, Problems, and Potential by Butt, Jackson, & Magan (2001) or Non-Chemical Weed Management: Principles, Concepts, and Technology by Upadhyaya & Blackshaw (2007).