Rust: Puccinia malvacearum

11 Friday Oct 2024

Posted by sconzani in fungi, plants, wildflowers

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Hollyhock rust, Mallow rust, Puccinia malvacearum, rust fungus, rust on mallow, Tree mallow

I was photographing the flowers of a roadside Tree mallow for a mid-autumn wildflowers-in-bloom blog that will be publishing this coming Sunday when I noticed the subject of today’s blog post, this new-to-me rust, Puccinia malvacearum. Its common names, Mallow rust and Hollyhock rust, provide the perfect indication for which plants are host to this fungus.

241011 Puccinia malvacearum (1)

As is typical with rusts, this species had created yellow-orange spots on the upper surface of the leaves and brownish lumpy pustules on the lower surface and on the plant’s stems. The rust would eventually reduce the plant’s vigour, leading to stunted growth and leaf loss, though, as this particular plant was growing in a location very likely to be mown regularly by council workers, the plant will probably be cut down long before it could succumb to the rust’s damage.

241011 Puccinia malvacearum (2)

Willowherb rust

21 Friday Jun 2024

Posted by sconzani in fungi

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British rust fungi, British wildflowers, Puccinia pulverulenta, rust fungus, rust on willowherb, Willowherb, Willowherb rust

I’ve probably ignored the yellowing leaves of various willowherb species when I’ve seen them previously, thinking they were just drying out or perhaps diseased, but this time I turned a leaf over and discovered a new fungus (and lots of tiny orange grubs – likely fungus gnat larvae – feasting on that fungus).

240621 Puccinia pulverulenta (1)

This is Willowherb rust (Puccinia pulverulenta) (luckily, most rust species are host specific so are easy to identify if you know what the host plant it). The tiny orange rings, which, with their white fringing look a little like miniature flowers, are aecia – it’s from these that the rust releases some of its spores. Later in their complicated life cycle, the rust also produces the brown uredinia that can be seen in the photo on the right below. (Rust fungi have five different spore states – if you want to delve in to that life cycle, Science Direct has a good explanatory, though very technical article on its website.)

240621 Puccinia pulverulenta (2)

Springtails and rust

21 Friday Apr 2023

Posted by sconzani in fungi, insects

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British springtails, Dog's mercury, Melampsora populnea, Merculiaris perennis, rust fungus, rust on Dog's mercury, springtail, springtail feeding on rust fungus

We’ve seen springtails and slime a couple of times previously on this blog; now here’s the next instalment in the springtails series: springtails and rust fungi. I spotted this rust, Melampsora populnea, on Dog’s mercury (Merculiaris perennis) during yesterday’s walk. From the top of the leaf, all you see is a small area of puckering and some pale spots (near the hole on the leaf in the lower part of the first photograph below). But, on the underside of the leaf, it’s a different story, with the orange blobs typical of a rust fungus.

230421 dogs mercury and rust

At the time, I didn’t notice the tiny creatures munching on the fungus, neither the minuscule orange ones nor the relatively large pale orange ones. I presume the smaller ones are the offspring of the larger, which are definitely springtails, though I don’t know which species of Collembola these are, and my photos aren’t precise enough to identify them more precisely.

230421 rust and springtails

Nipplewort Rust

26 Friday Feb 2021

Posted by sconzani in fungi, plants

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British fungi, Lapsana communis, Nipplewort, Nipplewort rust, Puccinia lapsanae, rust fungus

I was almost home from today’s 7-mile walk when I spotted the subject of this post, lots of pink gall-like bumps on the leaves of a group of plants I quickly realised were Nipplewort (Lapsana communis).

210226 nipplewort rust (2)

And that clinched the identification of the bumps, especially when I turned a leaf over and spotted the little yellow dots. These are the aecia, cup-shaped structures in which aeciospores are produced. (And, as you can see, this particular leaf was also home to a tiny spider.)

210226 nipplewort rust (3)

These Nipplewort plants were absolutely covered in rust fungi, Nipplewort Rust (Puccinia lapsanae), a rust I’ve seen before but never in such quantity.

210226 nipplewort rust (1)

Rusts: resplendent yet ruthless

31 Tuesday Jan 2017

Posted by sconzani in nature

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Puccinia acetosae, Puccinia circaeae, Puccinia coronata, Puccinia magnusiana, Puccinia phragmitis, Puccinia poarum, Puccinia sessilis, Puccinia species, rust, rust fungus, rust on plants

If you think rust only happens to metal, think again. These are rusts – actually fungi – that cause diseases in plants; anything from trees and shrubs in the local park to the fruit and vegetables you lovingly tend in your home garden can be affected by rusts, sometimes fatally. There are around 7000 species of rust but they are more readily identifiable than you might think as many are specific to particular plants – often it’s a case of name the plant, name the rust.

170131-puccinia-acetosae-on-dock

Rusts are most visible when they form disfiguring spots on the upper surfaces of leaves, and pustules on their undersides, as well as on the stalks and sometimes the flowers and fruit of plants. Just like most other fungi, rusts produce spores, in this case in their millions from within the pustules. Though they are the bane of most gardeners, rusts can be interesting and attractive fungi to examine and study. The photos shown here are: Puccinia acetosae on Dock (Rumex sp.) (above), Puccinia circaeae on Enchanter’s-nightshade (Circaea lutetiana), Puccinia coronata on Creeping soft-grass (Holcus mollis), Puccinia magnusiana on Buttercup (Ranunculus sp.), Puccinia phragmitis on Dock (Rumex sp.), Puccinia poarum on Coltsfoot (Tussilago farfara), and Puccinia sessilis on Lords-and-Ladies (Arum maculatum).