currant leaf spot

Symptoms

Small (1-2mm) dark brown angular spots on upper leaf surfaces, spots merge into irregular patches, premature yellowing + leaf drop from bottom upward, severely affected bushes are bare by August.

Easily confused with

• white pine blister rust

  How to tell them apart: On Ribes nigrum, Cronartium ribicola (white pine blister rust) shows raised yellow-orange powdery pustules on the LOWER leaf surface that later push out short brown bristle-like hair columns, each over a yellow halo on top. Pseudopeziza ribis (currant leaf spot) instead makes small, flat, dark-brown angular spots scattered mainly on the UPPER surface, with no pustules or hairs, that merge as the leaf yellows. Both trigger heavy early defoliation, but feel the underside: rust gives a bumpy, dusty, hairy texture while leaf spot stays smooth and dry. The orange dusty spores and brown hair-columns of the rust are the decisive sign — currant leaf spot never produces them.