Something on Hogweed

Plant diseases
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alindsay
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Something on Hogweed

Post by alindsay » Sat Aug 13, 2016 5:42 pm

Is this a rust growing on the Hogweed leaf or on the mildew?
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Chris Yeates
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Re: Something on Hogweed

Post by Chris Yeates » Sat Aug 13, 2016 11:18 pm

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
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Re: Something on Hogweed

Post by marksteer » Sun Aug 14, 2016 9:57 am

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
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Re: Something on Hogweed

Post by Chris Yeates » Sun Aug 14, 2016 2:43 pm

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
"You must know it's right, the spore is on the wind tonight"
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alindsay
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Re: Something on Hogweed

Post by alindsay » Mon Aug 15, 2016 4:43 pm

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
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Re: Something on Hogweed

Post by Chris Yeates » Mon Aug 15, 2016 5:54 pm

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
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Re: Something on Hogweed

Post by marksteer » Mon Aug 15, 2016 6:08 pm

I thought I had found something interesting on this host yesterday but turned out to be insect faeces!
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Re: Something on Hogweed

Post by alindsay » Mon Aug 15, 2016 7:21 pm

. these are the spore-producing bodies "chasmothecia" of the powdery mildew Erysiphe heraclei which is common on many umbellifer species.
Wow and ...... Wow!!!
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Re: Something on Hogweed

Post by Chris Yeates » Mon Aug 15, 2016 8:04 pm

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
"You must know it's right, the spore is on the wind tonight"
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alindsay
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Re: Something on Hogweed

Post by alindsay » Mon Aug 15, 2016 8:19 pm

...but where do the chasmothecia come from, if they are the start of the chain?

Alison

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