Hello, this juniper looks healthy, but its trunk is being covered by white stuff that is getting larger. It appears as if it is a fungus, but I would like a confirmation from you and, more importantly, recommendation for treatment if any exist.
Thank you for contacting Toronto Master Gardeners with your concern about the white coating at the base of your juniper. In recent years, we have noticed the symptoms shown in your photo, The problem ranges from what appears to be a powdery mildew on branches more than one year old, to the more heavy coating that seems to be your problem.
You may be experiencing a response by the plant to a natural cause such as drought, overwatering, or root injury. A close look at the photo suggests the openness of the area around the base may have that simple problem. Careful scraping away of the substance and added soil protection to fill in the spaces around the base may help.
If you sense there is something more serious, you may be witnessing a blight such as Kabatina juniperi. Fungicide treatment should be managed by a certified arborist. Many solutions could contain prohibited chemicals such as mancozeb.
Please contact Landscape Ontario for further assistance.
To explore more, select this site:http://hgic.clemson.edu
December 4, 2020