Arthuriomyces peckianus (Orange Rust of Brambles)
There are two species: the one in the title affects black raspberry, while morphologically indistinguishable Gymnoconia nitens affects blackberry.
Both photos (above & below) were taken at Governor Dodge State Park
Photo was taken at New Hope Pines State Natural Area
Both photos (above & below) were taken at Mecan Springs State Natural Area