Coniothyrium on Yucca?

Plant diseases
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jimmymac2
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Coniothyrium on Yucca?

Post by jimmymac2 » Mon Dec 23, 2019 4:13 pm

Today at Painshill Park in Surrey I came across just a single fungal spot on a leaf of a succulent which I think might be Yucca. Online research resulted in the possibility of Coniothyrium concentricum - does this look plausible? I managed to remove the fungus with a scalpel (trying to damage the plant as little as possible), so I'll be able to do microscopy on it if there are diagnostic features to look for.

Thanks, James
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adampembs
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Re: Coniothyrium on Yucca?

Post by adampembs » Mon Dec 30, 2019 2:19 pm

Did you find anything under the scope?
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Re: Coniothyrium on Yucca?

Post by jimmymac2 » Mon Dec 30, 2019 5:12 pm

The only clear structures I could see were masses of these small circular particles - spores?
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Re: Coniothyrium on Yucca?

Post by Paul Cannon » Tue Dec 31, 2019 12:27 pm

Assuming those "small circular particles" are around 4-5 µm diam., they are consistent with conidia referred to as Coniothyrium concentricum. However, it is likely to be a species complex, and related to Paraphaeosphaeria species that have also been implicated in leaf spotting of Yucca. So use the name if you like, but be aware that it is only an approximate identification.
The species is included in FRDBI as Microsphaeropsis concentrica, but both Coniothyrium and Microsphaeropsis are dustbins containing species with similar small brown conidia.
Enjoy...

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Re: Coniothyrium on Yucca?

Post by jimmymac2 » Wed Jan 01, 2020 10:09 pm

Thanks Paul, they are indeed 4-5 micrometers. I can see how leaf spots such as these are confusing taxonomically!

James
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