Beginner Gardening: Help! Disease? Centaurea macrocephala leaves, 1 by pfcosta

pfcosta wrote:
I wonder if you could help me identifying the problem. I couple of young C.dealbata developing plants show spoted leaves: winding white traces and small spots; some of the spots turned into granulous yellowish (picture enclosed). This developed gradually, starting with the white winding pattern. Patterns differ on upper and lower surface. Not all the leaves affected; cut out affected leaves. Is it a virus? I'm not experienced with Centaurea.