mik coffin's picture

Nettle clustercup rust

Observed: 3rd June 2012 By: mik coffin
3june12ivcp 021

Found this on a nettle stem. Can't decide whether this an egg mass, a lichen or whatever. It is about 1cm top to bottom


Caution: Do NOT use iSpot to identify fungi to eat!

Some fungi are very poisonous so a mistaken ID could have serious consequences.

Species interactions

No interactions present.


Fenwickfield's picture


needs to be put into the fungi section.


AlanS's picture

How do you know it is var. caricina?

As far as I know, unless one can be sure of the alternate host, the stage on nettles cannot be identified to variety.


dejayM's picture

Forced ID

Origin 18th June
I forced the ID panel to accept
Puccinia urticata as the Get Recommended proffers Puccinia caricina var. caricina.
The name is widely accepted by Recorders as P.urticata but there is still a lot of confusion.
Alan is probably right of course, this name might only apply to the fungus or the subsequent gall on Sedge or other host. Most of the web pictures show this on sycamore (sorry, black currant!), would you believe!
I am spending some time with a collected specimen at the moment - see

AlanS's picture

Something wrong

The identification "Puccinia caricina var. caricina" was wrong anyway.

The name "Puccinia caricina" used to cover the rust with its aecial stage on nettles, as well as a few other hosts, but "var. caricina" refers to a rust on Blackcurrant and other Ribes species.

Even when "Puccinia caricina" was more widely interpreted, var. caricina was a misidentification.

The named varieties of both P. caricina and P. urticata depend on their alternate sedge hosts.


dejayM's picture

on the case

Yes Alan, thanks. I am on the case at the moment because I find it fascinating. I fret a little because the growth is a gall, (which may not have a name)and the rust, so called, it to do with its appearance. The fungus is all display but I assume infects the nettle plant, not just a lesion.
The name Puccinia caricis-urticae is written in some early history (BHL site) but fairly quickly became (and accepted as) P.urticae (after 1873).
Can you point me to a sourse that explains >"The named varieties of both P. caricina and P. urticata depend on their alternate sedge hosts" please. "..depends.." suggests that it cannot reproduce without them.
I am using the online >>BHLibray)<< - a real blessing.

AlanS's picture


Perhaps I was slightly sloppy in my choice of words.

I should have said that certain identification of the named varieties of P. caricina and P. urticata depends on knowledge of their alternative hosts. The varieties of P. caricina are apparently indistinguishable when on Ribes, and the same applies to P. urticata on nettles. Actual P. caricina var. caricina, which alternates with Carex pseudocyperus, is apparently rare in Britain. [Users of the BMS database should note they have got this seriously wrong, apparently a fine example of what I call the "nominate subspecies problem", http://www.lichens.lastdragon.org/faq/nominatesubspeciesproblem.html , and at some point I am going to send them a telling off.]

When the rusts are on sedges, the identity of the particular sedge host is essential for identification of the rust variety, but there are also differences in spore size.

There are certain genetic strains within this complex that may be able to survive and reinfect their particular sedge hosts, but the spores (aecial stage) produced on Urtica or Ribes cannot reinfect the same host and must cycle with the sedge host.

Varieties of P. caricina and P. urticata are described in the standard work on British rusts: Wilson & Henderson (1966) 'British Rust Fungi', probably not online anywhere but available as a reprint. Wilson & Henderson treated them all under P. caricina, and the modern re-splitting off of P. urticata follows from the more recent work of a guy called Zwetko.

I have not seen Zwetko's publication yet, though I have it on order.


dejayM's picture

World dictator designate

Alan, that is very welcome, thanks. As an average broad-interest Naturalist I may not be able to go far along this trail but, nevertheless, I'll try!
You will see in my post (I know you have been) http://www.ispotnature.org/node/417828 that I have gone as reasonably far photographically this season as possible. It is supposed to be absent from Orkney but I have found it widespread this year and may have been here for as long as nettles!
I am now paying far more attention to rusts in general. Thanks again.