My lilac bush has a powdery mildew on several branches. Should I trim those branches off? Leaves don't look good.
It is safe to cut those branches. You will want to treat the plant, and the area around it though. There are several things you can do. Use wettable sulfur in the soil, these plant oils will also help: Lavender oil, garlic oil, rosemary oil, and neem oil are good treatment options. Here is an article that will help: https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm