powdery mildew on lilac?
I have a small lilac next to my vegetable garden that appears to have powdery mildew, the same thing that got to my zucchini previously. I'm thinking of treating it, even if it doesn't need to be treated, to prevent it from contaminating other vegetable plants. Thoughts?
Some types of powdery mildew are generalists and will spread to multiple host plants. In this case, the powdery mildew on lilac is not a generalist that would spread to your zucchini. They are different species of mildew.
That said, it is late to treat powdery mildew on lilac. A horticultural oil or registered fungicide can be used to control powdery mildew, but it is more effective when applied before major symptoms appear. https://extension.umd.edu/hgic/powdery-mildew-trees-and-shrubs
The best way to deter powdery mildew on zucchini is to plant varieties that have resistance to the fungus. Cornell University maintains a good list of vegetable varieties with disease resistance. Look at their list under "Zucchini squash" for some powdery mildew resistant choices. http://vegetablemdonline.ppath.cornell.edu/Tables/TableList.htm