I am not putting this here to say no but before I found a non-toxic product that works I asked question about milk and other items that some said were myth and some said were the best thing since white bread.
Here is what the pros say.

https://puyallup.wsu.edu/wp-co...

Interesting article. I will say that I never have aphids when using the milk. I'm not sure if it is the actual milk, or the oil and soap that I add to the milk. And I did try it on powdery mildew on zucchini once. It might have worked, not sure - the actual infected leaves died and I cut them off. The new leaves were healthy - not sure if that was due to the milk, or if they would have been healthy anyway. I think the milk works more as a preventative than a cure.