shrub disease or parasite?

Asked August 5, 2015, 3:56 PM EDT

I have a weblike substance that is growing on boxwoods. I notice it is getting worse and appearing on several flowering plants. Is this a spider or mite, or is it a disease? How harmful is it? How do I combat it?

St. Louis County Missouri trees and shrubs forestry horticulture horticulture

1 Response

Without a picture it is hard to tell what it is. Spider mites will make a webbing on the undersides of plant leaves. When you tap the leaves over a white piece of paper, the mites will fall off. Powdery mildew is a white powdery substance that grows on plant leaves in a rainy season. It could be that. It can eventually kill plants such as pumpkin vines and squash plants. I doubt if it will do much harm to a boxwood. You can upload photos to this. So if you can, send a photo. Or, you can take it to your county extension center for identification. Without knowing exactly what it is, it is hard to tell you how to control it and if it is going to kill your plant.