Nodulosphaeria derasa

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Chris Yeates
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Location: Huddersfield, West Yorkshire

Nodulosphaeria derasa

Post by Chris Yeates »

A relative of the previous species in this subforum (i.e. another member of the Phaeosphaeriaceae). I think this must be very common as I collected it yesterday on a dead stem of common ragwort, Jacobaea vulgaris virtually in my garden. Look for dead stems of the plant (fairly easy) and then look for black dots (x10 loupe) about half way up the main stem, around where it branches. The fungus might occur on all parts of the stems, but that is where it have seen it most frequently. This was in perfect condition despite the stem being totally dry and following all the recent hot weather.

I have found the mini version of the sort of misting water spray hairdressers use to be very useful to make material easier to deal with. Leave for a couple of minutes and then if the black dots are carefully extricated (v. fine forceps are best for this), mounted in water and with slight pressure applied to the coverslip, under the microscope you can quickly see if you have been successful. It might prove to be another fungus, but this is something of a Jacobaea / Senecio specialist. It is easily identified - the fourth cell from the apex is swollen (hence "Nodulosphaeria") and the spores usually have a distinctive strongly deflexed appendage at each end as can be seen in the image here. A composite can be found here http://www.ascofrance.com/base-de-donnees-fiche/4879 (click on thumbnail).
2021-06-20-21.24.44 ZS.jpg
2021-06-20-21.19.44 ZS.jpg
Chris
"You must know it's right, the spore is on the wind tonight"
Steely Dan - "Rose Darling"
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