White spots on oak leaves

Hi all,

My oak seedlings both have white ‘spots’ as in the picture. It looks a bit like a fungus I guess and when I wipe it, it leaves a darker spot, picture 3.
Now I seem to remember reading about this before and spraying milk/water mixture was recommended for it. Not sure if it was exactly the same though, hence my question.
Thanks,
Peter

yup, mildew. Spray with a 50/50 mixture of water/milk. Repeat in a week or 2