My crape myrtle looks like it has mildew or a fungus, white spots on the...
My crape myrtle looks like it has mildew or a fungus, white spots on the leaves. I don't see any critters. IThe plant is well established, about 10 years old. The tree is in sun part shade. everything else near it looks healthy, no disease evident. If it is a fungus, can I treat it with copper soap? I estimate the change occurred within the last week.
It probably has powdery mildew, a fungal disease. Please read the following information from our Tree and Shrub problem section: https://extension.umd.edu/learn/powdery-mildew-trees-and-shrubs
Keep in mind that horticultural oil cannot be sprayed when the temperatures are very high. Read the label!
Fungicides are not curative. They are preventative. Try to change the environmental of the crape myrtle so it does get the problem at all. Next year, keep an eye on the crape myrtle and spray as soon as you see the first spot.
Recently, research has shown that fungicides other than horticultural oil are toxic to bees and other pollinators. Never use a fungicide on a plant that is currently in bloom.