Tonya Smith posted this picture of a fungus on a violet leaf. I asked Mark Bower to educate me as my knowledge of these fungi is a bit rusty.
Sorry....but not really.
"Rust fungi are highly specialized obligate parasites on plants. There are at least 7,000 species known, and most are in the order Pucciniales, one of the largest orders of the fungal kingdom. They are call rusts because many of them are orange colored, although they can be black, brown, yellow or red.
Rust fungi have complex life cycles, frequently including up to five spore stages and two different alternating plant hosts. They are responsible for a variety of diseases of agricultural crops. They are important pathogens of cereals, legumes, fruit trees, coffee plants and many others." Mark Bower
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| Puccinia violae on a violet |
Tonya said, "That photo is deceiving. The square stem is a different plant. The rust I found was on violet leaves."
Tonya's rust above is
Puccinia violae, a violet specialist. Like mosquitoes, rusts don't get much respect in online resources but there are photos of their life stages at Discoverlife. Viewed up close, it has its own special beauty.
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| Cedar apple rust |
The most dramatic example of rusts in the Ozarks is the cedar apple rust
, Gymnosporangium juniperi-virginianae, which causes orange, gelatinous growths on eastern red cedars. To complete its life cycle this fungus requires an alternate host such as an apple, service berry, hawthorn or pear tree. It "fruits" after rain before shrinking into a brown hard lump.This isn't a serious problem unless you have an orchard and affects your fruit.
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| Cedar quince rust |
Cedar quince rust is caused by
Gymnosporangium clavipes. It spreads along the branches resembling witch's butter fungus. Aside from a bright orange to brighten up an overcast day after a rain, it doesn't have beauty to recommend it. It affects a much wider variety of plants in the rose family, 480 species at last count. More on
G. clavipes in this blog.
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| Mayapple rust |
Another common but hidden rust is Mayapple Rust, caused by
Allodus podiphylli. It occurs on the underside of the leaf but a small tan dimple on top can help you find it without looking under every plant. Mayapples are a very interesting subject that we covered in
this 2015 blog. More details about this rust is
here.
