Dark, powdery dots on the underside of last year's blackberry leaves.
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.
There are two purple rusts on Bramble, but the other (bulbosum) has much smaller spore-clusters that these, so I think even without the microscope you are safe. As a rule, P. bulbosum is only on one group of the very complex Rubus fruticosus aggregate, and on R. caesius.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
Lat/Lng: 50.592, -2.468
OS grid ref: SY669770
A great mass of brambles by the sea.