This rust causes galls on Creeping Thistle (Cirsium arvense), and the whole plant appears stunted.  There is no host alternation.  Sickly-smelling yellow spermogonia are followed by brown aecia covering the leaf underside; light brown uredinia and darker brown telia are present later.

other species of Thistle are affected by different species of Puccinia

host

Photograph the rust on the host.  Ensure you have noted the host-plant species in your comments

on Creeping Thistle