Oak disease, help :(

Hello friends, I want to ask kindly for someones expertise on my beloved oak-tree I'm trying to grow in a pot to one day plant in my future garden.
I grew it from a acorn for about 3 years and put it outside on my grandma's balcony during the summer. When I came back after travelling it looked like this.
I don't know what the issue is but wanted to turn to the experts in order to save it. Is it overwatered? Milky mildew? Not used to be outside?
Worth knowing is that the leafes here grew out earlier in late winter from a pot inside an appartment, so could be that they are old in their cycle?

I want to learn and save my oak-friend!

Thanks alot and congratulations to this beautiful forum.

A

I am not sure what is going on with that oak.

It could possibly be a fungal infection.

My suggestion would be to use a fungicide to see if that helps.

I have a simple recipe that uses easy ingredients:

A really good treatment for powdery mildew is: 1 gal water, 1 T dish soap, 1 T baking soda.

I put it in a spray bottle to make applying it easy.

Some recipes call for adding oil. I have never found a need for the oil.