Mildew on squash
Every year, my squash gets mildew. I have a drip system and it is planted in a raised bed located on the south side.
Personally, I prefer rosemary oil for a systemic treatment every year through your drip, but for spot treatment, I would recommend neem oil, as long as you do not spray in full sun. This article will help: https://www.gardeningknowhow.com/edible/vegetables/squash/powdery-mildew-in-squash.htm