Powdery mildew is another type of fungus that thoroughly enjoys our humid Maryland and Virginia climate—particularly during a dry spell accompanied by moderate (below 90-degrees) temperatures and high relative humidity. That’s because powdery mildew requires a dry leaf surface to form.
There are multiple types of powdery mildew and each one favors a particular species of plant. So, if your lilacs are affected, that mildew will stay put and not spread to your peonies or other species.
The fungus won’t kill a plant unless you allow it to progress for several years without treating it. In that case, it would gradually interfere with growth, distort plant shape and cause leaves to drop prematurely.
