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How Rust is a Fungus
Rust is a common name applied to any of a group of parasitic fungi that form orange-red spores on the stems and leaves of the seed plants. Rusts make up the order Uredinales. Some rusts produce galls, and others cause the formation of crowded, tufted shoots called witches'-brooms, sometimes contrubiting to fasciation (that cool thing that happens when a plant goes nuts and produces an elongated distorted flower stem. Rusts rarely kill plants but often produce dwarfing, discoloration or other general weirdness. It can open the door to powdery mildew and other plant problems.
There are many types of rust, but three are most common in the garden. Rose rust is found on anything in the rose family, including fruit trees, blackberry vines, and all kinds of perennial flowers including Geums and Potentillas and shrubs like Spireas, Photinias and Physocarpus. Mint rust can quickly wipe out a small collection of mints. Chocolate, Ginger and Candy Mint are the most succeptible. The best prevention is being aware of what rust looks like upon purchasing a pot of mint -- from the garden store and nursery is where most of it comes from. Once in the garden, don't feed your mints much at all. It's lots of lush new growth that really spreads the rust. Hollyhock Fungus for some reason only really infects Hollyhocks, although I'm sure if it were under duress a Lavatera, Hibiscus or other Mallow might succumb. Often overlooked is Daisy rust, or at least that's what I call it, because it infects many plants in the Asteraceae, also known as the Compositae family. Areas rich in Goldenrod might get this one coming into gardens. It shows up on Dahlias on the underground part of the stem first. On Stokesias it makes dark burgundy streaks on the leaves. This is so common that is is thought of as normal -- in the Pacific Northwest nary is seen a Stokesia in a nursery or garden store without this affliction, and normally it goes away when the weather warms up. Sometimes you will even see Dandelions get it. There are many rusts of conifers, as well as rusts of lawns and grasses in general. Most of the ornamental grasses can get corn and wheat rusts, but it's not common except in the deep south where Sweet Corn often gets pretty bad Honey Fungus, which is yellow mottling on corn, but can show as orange or yellow blisters on Sorghastum, Arundo and some other grasses. Go To Page: 1 2
The copyright of the article Perennial Rusts in Perennials is owned by Jojo Sigurgeirson. Permission to republish Perennial Rusts in print or online must be granted by the author in writing.
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