Yes... And it has to have the sun with intense UV and it turns the milk into a antibacterial. Or antiseptic.i've heard you can yous diluted milk to get rid of powdery mildew
I've used it many times the only thing is...is that the Shaded side of the plant. it don't usually work too well on that side cuz the sun doesn't get to it too well.
But it does work on the sun side for sure.
Also the h202 works very well. And the plant love the extra 02.