Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
Certainly the right genus, and probably (on the basis of size of the spore-clumps) P. violaceum. P. bulbosum tends to have much smaller patches and less obvious red marks above.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
I heard that one of the species was more of a generalist, whereas the other was tied to one or only a few species, is this correct?
P. violaceum is on R. fruticosus agg., except for the Section Coryliifolia. P. bulbosum is on that Section and on R. caesius. There is an easy difference in the spores - see http://www.hbrg.org.uk/SotM/Phragmidium.html.
The host distinction is highly but not completely reliable.
Yes, on section Corylifolii and R. caesius I, personally, have found only P. bulbosum. (Section Corylifolii is derived from hybrids of brambles with R. caesius, so the rust is showing itself to be a good taxonomist.)
And almost always, the rust on other brambles is P. violaceum.
However, several years ago, on a BMS meeting in central Ireland, I came across a hybrid bramble, between R. ulmifolius (the one truly sexual species in the true brambles and so able to hybridise with others) and R. vestitus. Clearly the poor bramble had not inherited rust resistance from either parent and it was infected with BOTH these Phragmidium species.
Lat/Lng: 54.2596, -0.4126
OS grid ref: TA035860