Powdery mildew is unsightly and can weaken a plant but rarely kills it.

It overwinters on fallen leaves and stems so fall clean-up/sanitation is important.

If conditions are just right, warm days/cool nights it can continue to be a problem and become heavier.

Like most diseases, severity can be lessened a bit. Anything you can do to keep good air circulation and plenty of sun is good. Try not to water overhead. Anything that keeps the leaves able to dry off as soon as possible. Don't handle the plant when the leaves are wet to reduce spreading.

There are disease resistant varieties, do if you add plants, look for these.

Again, if leaves are covered and no green tissue exists in late summer into fall, remove and destroy dead leaves and stems in the fall so there is less pathogen in the garden next season.

Christine