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Something on Hogweed

Posted: Sat Aug 13, 2016 5:42 pm
by alindsay
Is this a rust growing on the Hogweed leaf or on the mildew?

Re: Something on Hogweed

Posted: Sat Aug 13, 2016 11:18 pm
by Chris Yeates
Hi Alison
I'm not sure that it is either; the rust, Puccinia heraclei, despite the ubiquity of its host is extremely rare - I've only ever seen it once despite a lot of looking: https://data.nbn.org.uk/Taxa/NBNSYS0000021905 (that dot on the Northumbrian coast). And the powdery mildew, while very common, doesn't look look this (although the images are not very helpful). In the absence of a macro-lens / dissecting scope if you have a scanner, you can get pretty detailed images of this sort of fungal(?) attack . . .

I've never seen anything like these dark blotches on hogweed leaves :?

Chris

Re: Something on Hogweed

Posted: Sun Aug 14, 2016 9:57 am
by marksteer
Interesting - I didn't realise there was potentially a Rust on this species. Looking at Wales Red Data list Rusts it is considered to be Regionally Extinct last record 1964 in Wales. In Dutch Rust Fungi suggests ' UK possibly rather common, especially in N. and W. England' which is perhaps not correct. FRDBI has 98 UK records

Re: Something on Hogweed

Posted: Sun Aug 14, 2016 2:43 pm
by Chris Yeates
marksteer wrote:Interesting - I didn't realise there was potentially a Rust on this species. Looking at Wales Red Data list Rusts it is considered to be Regionally Extinct last record 1964 in Wales. In Dutch Rust Fungi suggests ' UK possibly rather common, especially in N. and W. England' which is perhaps not correct . . . .
In "A Fungus Flora of Yorkshire" (1985) Bramley writes: "Considering abundance of host, must be considered rare. At Ellerburn Nature Reserve, Thornton Dale, it has not spread from a few square yards in the last ten years."
marksteer wrote: . . . .FRDBI has 98 UK records
It's interesting to have a close look at those records: 30 of them are 19th century ones; and four of them have (obviously erroneously) Taraxacum as the host.

Chris

Re: Something on Hogweed

Posted: Mon Aug 15, 2016 4:43 pm
by alindsay
Thanks Chris.

Apologies for the unhelpful photos, but I now have access to better photos (computer problems) and I see that the black and orange dots I found do not have the look of rust at all, but are intriguing little spheres.

Probably aliens then!!

Alison

Re: Something on Hogweed

Posted: Mon Aug 15, 2016 5:54 pm
by Chris Yeates
alindsay wrote:Thanks Chris.

Apologies for the unhelpful photos, but I now have access to better photos (computer problems) and I see that the black and orange dots I found do not have the look of rust at all, but are intriguing little spheres.

Probably aliens then!!

Alison
Hi Alison
sorted . . . . these are the spore-producing bodies "chasmothecia" of the powdery mildew Erysiphe heraclei which is common on many umbellifer species. The powdery mildewy bit is often more in evidence on the upper leaf surface with the chasmothecia predominating on the lower surface.

Under the microscope the appendages of the spheres of some species can indeed be rather wonderful (click on thumbnails to enlarge):
http://www.ascofrance.com/search_recolte/3991
http://www.ascofrance.com/search_recolte/3883

For aliens look no further than the wonderful illustrations produced in the 19th century by the Tulasne brothers* - especially of the genus now treated as Phyllactinia:
http://2.bp.blogspot.com/-PgaobX5tRcI/V ... uttata.jpg (Image should enlarge with the + sign). The Phyllactinia on ash is getting quite common with (most probably) climate change.

best wishes
Chris

* https://en.wikipedia.org/wiki/Charles_Tulasne

Re: Something on Hogweed

Posted: Mon Aug 15, 2016 6:08 pm
by marksteer
I thought I had found something interesting on this host yesterday but turned out to be insect faeces!

Re: Something on Hogweed

Posted: Mon Aug 15, 2016 7:21 pm
by alindsay
. these are the spore-producing bodies "chasmothecia" of the powdery mildew Erysiphe heraclei which is common on many umbellifer species.
Wow and ...... Wow!!!

Re: Something on Hogweed

Posted: Mon Aug 15, 2016 8:04 pm
by Chris Yeates
alindsay wrote:
. these are the spore-producing bodies "chasmothecia" of the powdery mildew Erysiphe heraclei which is common on many umbellifer species.
Wow and ...... Wow!!!
It's things like that which explain why people such as I don't treat toadstools as the only fungi worth looking at ;)

C

Re: Something on Hogweed

Posted: Mon Aug 15, 2016 8:19 pm
by alindsay
...but where do the chasmothecia come from, if they are the start of the chain?

Alison