#rust fungus

[walkingthewetlands]

11/16/2025, Southeast Virginia

I love finding things in a state of decay. Green juxtaposed with withering brown. Fungi dotting the plant. Part of the natural processes

[ifelten]

Nældegalle-Tvecellerust (Puccinia urticata)

På stor nælde (Urtica dioica).

Nettle Clustercup Rust Fungus (Puccinia urticata)

On Stinging Nettle (Urtica dioica).

[microcosmicobservations]

Rust fungus (Puccinia sp.) growing on biscuitroot (Lomatium dissectum)

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[newportlife]

[regnum-plantae]

Puccinia urticata on Urtica dioica

It’s hard to walk by banks covered in common nettle without noticing this fiery and gruesome rust fungus taking hold of and deforming the plant’s limbs. 

It’s best described as a species complex with a life cycle which might alternate between two hosts- in the British Isles often a nettle (U. dioica or U. urens) and a sedge (mostly Carex sp.), but its ‘sub-species’ can also be found on Aster and Ribes.      

Here you can see some beautiful up-close photos of its structures.   

[drawrty]

Les couleurs du temps (2) by EveDubos

[drhoz]

#1239 - Miyagia pseudosphaeria - Sonchus Rust

And then, tonight, as I was getting these photos together to post on my blog, I noticed that many of the Sowthistle leaves had little yellow pimples on them, surrounded by dark pinkish rings - it soon figured out that it’s a another specialist, the Sonchus Rust Fungus (Miyagia pseudosphaeria).

The fungus was first noticed in Australia 20 years ago or so, but has no real effect at controlling the weed. Nor are the aphids, and their predator has its own problems, in the form of the wasp. True, it all reaches a balance eventually, but that balance is an invasive weed occupying habitat better reserved for Australian native plants, if you can find any that will survive beside driveways.

[microcosmicobservations]

Rust fungi can be terrible agriculturally but are fascinating nonetheless. This is Gymnosporangium sp. growing on juneberry fruits. All species of Gymnosporangium have two hosts where their life cycles are divided. The primary host is the juniper tree, where it fruits and produces spores to infect the secondary host - in this case, a juneberry tree. The white parts are spore tubes, and the orange dust is the spores.

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