Mildew on Comfrey

Plant diseases
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Simon Horsnall
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Mildew on Comfrey

Post by Simon Horsnall » Mon Sep 14, 2015 4:06 pm

Perhaps a few words of introduction wouldn't go amiss as this is my first post on the site. I am a WAB exile although not very active on the fungi pages. My main interests are birds and insects and I co-ordinate the National Siphonaptera Recording Scheme. In addition to this, I am a pan-species lister so take a passing interest in fungi although recognise most are well beyond my current level of competence. Anyway, I've recently been drawn to rusts as my botanical knowledge is a lot better than my mycological and I figured that if I could identify the host I have gone a long way towards identifying the fungus. After a conversation with Alan Outen, he suggested I could apply a similar strategy to mildews and smuts. In looking for suitable literature, I ended up here.

The comfrey plant in our garden (an invader from next door) has been overtaken recently by a mildew. Having searched, the only species I can see affecting comfrey is Erysiphe cynoglossi. Is that a safe conclusion or are there other species? If there are others, is there anything I can do to determine species or is it an "Oops, I've dropped it" scenario?

I can probably get photographs when it stops raining if it helps.

Simon

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Lancashire Lad
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Re: Mildew on Comfrey

Post by Lancashire Lad » Mon Sep 14, 2015 7:33 pm

As I understand things, (not being well versed with mildews), Erysiphe cynoglossi, now named Golovinomyces cynoglossi, (605 British records), is the only powdery mildew that affects symphytum. - But there is also the downy mildew - Peronospora symphyti, (41 British records).

Good close up photos of both upper and lower leaf surfaces will give us an idea of what yours looks like macroscopically.

Regards,
Mike.
Common sense is not so common.

Simon Horsnall
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Re: Mildew on Comfrey

Post by Simon Horsnall » Mon Sep 14, 2015 8:57 pm

Many thanks for the swift reply. I doubt these are good enough but anything better will need daylight now.

The upper surface of the leaf:
mildew on symphytum upper.jpg
A detail of the leaf hopefully showing the structure of the mildew and what I presume to be the sexual stage of the mildew (little black spherical objects):
Mildew on Symphytum detail.jpg
The underside of the leaf:
Mildew on Symphytum underside.jpg
Ever optimistically
Simon

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Chris Yeates
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Re: Mildew on Comfrey

Post by Chris Yeates » Mon Sep 14, 2015 11:34 pm

Hi Simon
yes I think you have what is now called Golovinomyces cynoglossi (Wallr.) V.P. Heluta there. What one can see is affected by the extensive patches of dead leaf tissue. For the sake of newcomers to this area of mycology these can cause confusion; in species like this the swollen hair-bases look like they may be signficant, forming tiny white swellings - they're not . . .
There does appear to be the characteristic white 'mildew' of the anamorphic stage in some of the photo's. I think that in the last image the most conclusive factor is what look like chasmothecia (cleistothecia / ascospore-forming bodies) a third in from the left and above the main leaf vein. If you could show either the white 'mould' stage on healthier leaves, or more convincing chasmothecia it would clinch it; that said this fungus is common on comfreys and so it is likely you have found it.
best wishes
Chris
"You must know it's right, the spore is on the wind tonight"
Steely Dan - "Rose Darling"

Simon Horsnall
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Re: Mildew on Comfrey

Post by Simon Horsnall » Tue Sep 15, 2015 5:20 am

Thanks Chris. I shall try to get out with the camera today, although the whole plant is looking pretty sickly. However, I did look at this down the stereo microscope. As you say, I identified the swollen hair bases as such but there is definitely, and you will have to excuse terminology here, some form of black, spherical body inside the white mass, supported above the leaf surface. When looking at it, it reminds me very much of the mould which forms on badly curated insect specimens: a white, fibrous mass with the small black bodies in it.

Anyway, I'll tentatively label it as G. cynoglossi pending further photographs.

Simon

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Chris Johnson
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Re: Mildew on Comfrey

Post by Chris Johnson » Tue Sep 15, 2015 8:07 am

Hi Simon, welcome to the forum. I'm sure forum members will be pleased to call on your Siphonaptera knowledge occasionally.

Golovinomyces cynoglossi is on our comfrey as I write, as indeed is Melampsorella symphyti, Comfrey Rust. Very obvious in bad years such as this cool, wet summer.

A couple of links appended that may help.

Regards, Chris

http://outerhebridesfungi.co.uk/species.php?id=330
http://outerhebridesfungi.co.uk/species.php?id=136

Simon Horsnall
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Re: Mildew on Comfrey

Post by Simon Horsnall » Tue Sep 15, 2015 1:02 pm

Thanks for the welcome and the links Chris. I'm more than happy to help with Siphonaptera, although photographs are not really a good way of going about it.

I'm hoping these are better (suitable) photographs. About the only healthy leaf on the plant.

Upperside
Picture 016.jpg
Underside
Picture 015.jpg
I scraped some of it onto a slide and had a look under the microscope. This looked an interesting structure. Approx 130 microns by 80 microns, each individual part 80 microns by 35 microns. The "stalk" approximately 12 microns width.
Picture 001.jpg

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Chris Yeates
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Re: Mildew on Comfrey

Post by Chris Yeates » Tue Sep 15, 2015 1:22 pm

Hi
yes, no doubt about it those dark bodies are chasmothecia (fruiting bodies / sexual stage). The micro shot shows asci presumably squashed out of a fruiting-body. The "stalks" are actually mycelial threads / appendages that happen to be in the mount.
Sometimes the appendages can be quite something - these are on oak leaves and snowberry leaves respectively:
http://www.ascofrance.com/search_recolte/3883
http://www.ascofrance.com/search_recolte/3991
(click on thumbnails)
The latter "plate" shows (bottom left) a chasmothecium, split by light pressure to show the asci inside and some free ascospores.
Regards
Chris (Y)
"You must know it's right, the spore is on the wind tonight"
Steely Dan - "Rose Darling"

Simon Horsnall
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Re: Mildew on Comfrey

Post by Simon Horsnall » Wed Sep 16, 2015 3:30 pm

Many thanks to all those who have helped with this one. I shall once again apologise for my terminology but I am a real newcomer to this area (before the start of the year I had a fungus list of one: Amanita muscaria, I'm now on 22). Over the autumn I am hoping to start to get to grips with the genera of Agaricomycetes.

One final question before I slink back to my 20+ bags of birds' nests. If I were to collect say an Agaricus, photograph it and dry it, would I be able to come back to it in a year, 5 years, 10 years and get further with the ID or would the necessary features be lost? I don't like posting lots of "What's this please" type posts without at least trying first.

Simon

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Re: Mildew on Comfrey

Post by Lancashire Lad » Thu Sep 17, 2015 10:46 am

Simon Horsnall wrote: . . . .One final question before I slink back to my 20+ bags of birds' nests. If I were to collect say an Agaricus, photograph it and dry it, would I be able to come back to it in a year, 5 years, 10 years and get further with the ID or would the necessary features be lost? I don't like posting lots of "What's this please" type posts without at least trying first.

Simon
Hi Simon,
Probably not a definitive answer, as with some species, certain characteristics, (Hans Otto Baral describes such as "vital taxonomy"), can be destroyed by drying, and require the examination of fresh examples.

But in general terms, yes - if fungi are thoroughly dried and properly stored, then samples can be rehydrated, and most of the original microscopic characteristics can be examined quite adequately in the years to come.

There is discussion here on the subject of preserving fungi samples for future use, along with some useful links: - viewtopic.php?f=3&t=447

Regards,
Mike.
Common sense is not so common.

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