Forum Flora Germanica

Coleosporium maybe but fishing in dark.
Single occurrence exactly on this needle, as on photo, all around all healthy.

http://agrozoo.net/jsp/Galery_one_image ... 34c0ce5bb1

Looks like a good match.
The exact species will remain unclear, as the main stages occur on different herbaceous plants.
https://www.arbofux.de/kiefernnadelrost.html