Not 100 percent sure, but probably a fungus called melanose, which is normally black spots, but in some areas it has a white fungal faze. . Just wipe it off with a mild soapy solution.

This is there on all oranges on the tree. I can’t see any blacks but will try the soapy solution. Thanks.

I did check some google images for Melanose but these definitely are different.

I don’t have any experience with oranges, but this looks to me like “bloom” (cuticle wax). Many fruits, especially those with thick skin, produce a delicate crystalline wax that looks like a thin dusting of white powder. It is healthy and normal.

Thanks Tiffany