The aecial stage is on Pear (Pyrus).  Small spermogonia pustules appear on leaf surfaces in Spring, followed by aecia on leaf undersides.  These are swollen galls, bearing large orange-brown aecia which open to release spores through longitudinal slits.  These remain as skeletons after the spores are shed.   There are corresponding bright orange-red blotches on the leaf uppersides. 

The primary telial host is Juniper, on swellings on branches.  The telia are conical, and yellow-brown when wet. 

on Pear

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

alternates between Juniper and Pear