Black Stem Rust - Puccinia graminis

Streaky rust-brown uredinia appear on the leaves, leaf sheaths, stems and glumes of the primary hosts, grasses and cereal crops. Later, darker telia appear,  particularly on the leaf sheaths and stems, but are not gall-causers.

The alternate host is Berberis or Mahonia, and is rare, and a gall-causer; the rust causes raised areas on fruits and undersides of leaves, yellow to orange-red to purplish; bearing spermogonia and aecia only. 

Several similar rusts affect Berberis and various grasses

host/microscopy

Photograph the rust on the host.  Ensure you have noted the host-plant species in your comments.  Microscopic examination will be needed.

Alternating generations between Berberis and various grasses and cereals.