Friday, 22 January 2016

Some Easy Microfungi for Mr Bell's 1000

I was out this afternoon and came across four microfungi, which as they are easily identified in the field, with no more than a hand lens, I thought would be of use to Martin in his PWC.

The first is Appendiculella calostroma, which causes dark, blotches on the surface of sheltered bramble leaves at this time of year. The blotches often merge together to form blackened, sooty looking areas on the upper surface of the leaves and stems. Look closer and you will see that each blotch is a diffuse, dark web, with black blobs on it, near the middle.

It looks shiny in this pic, because the leaf was wet, When dry it is matt.
Under the microscope it looks like this, but it is distinctive enough in the field to make using a microscope unnecessary.

Don't be fooled bt the purple spots that are common in brambles, Those are caused by the rust Phragmidium violaceum. The easy way to be sure is to look underneath the leaf. The purple spots of P. violaceum are visible on both sides, with a black felty looking spot (the spores) often present in the middle of the spot under the leaf. A calostroma is usually found only on the upper surface and can be scraped off.

If you look closely at Herb Robert (Geranium robertianum) at the moment, you will sometimes find lots of these tiny black dots on the leaves and petioles. It is a microfungus called Coleroa robertiani.

The black dots are the fungus. What the springtails are eating, I don't know.
If you examine ash keys, picked up off the ground, you will see small black dots on the surface. A closer look will reveal that those on the thick part are larger than those on the wing. That is because they are two different fungi. The one on the wing is always Phoma samararum (Stagnospora samarorum) and the ones on the seed end are Diaporthe samaricola (it has has a name change).

Two for the price of one. Diaporthe samaricola on the thicker areas and the much
smaller Phoma samararum (Stagnospora samarorum) on the thin wing area.
I hope this helps in getting to your 1000 species. By the way, I've just found out that the large blotches you see on ivy leaves are Phoma hedericola.


  1. Cheers Mark, I've had the Bramble leaf Rust previously.

  2. Thanks for this post Mark, it was useful in working out what caused the black spots on Herb Robert in our garden.

    What reference are you using for IDing these...Ellis & Ellis?

    ALso worth pointing out that there is another Phragmidium on bramble (P. bulbosum) - you have to look at the shape of the spores to be sure which you have. So far all the ones I've examined have been violaceum.

  3. Ellis and Ellis for the general microfungi, George, but for the Rusts I prefer 'British Rust Fungi' by Wilson and Henderson and 'Roesten Van Nederland' (bilingual) by Termorshiuzen and Swertz.

    I have alsofound P. bulbosum, but it doesn't seem that common around here and when found the appearance is subtly different fro P. violacaeum. With violacaeum, the clusters of spores tend to be larger and more robust than in bulbosum, which I've found to be smaller and more scattered, often with only faint spots visible on the upper surface of the leaf. The spots with violacaeum are nearly always bold and purple. There is nothing scientific about that, it being very much a gut feeling, based on experience so if I suspect it might be bulbosum, I always take a specimen home to look at the spores.