I may have an issue with boxwood blight . Can I preventively treat with propiconazole -a DMI . Can I still treat in Montgomery County. Any suggestions. These are Justin Bauer boxwoods ~200 -part of a Knot garden. They look pretty good but I have Accent boxwoods at corners (Green Mountain boxwoods ) which have some dead leaves and a few red leaves. I'm just concerned. Any suggestions?
Montgomery County Maryland
We'd recommend that you send us photos of the dead and red leaves on the plants, so that we can help you diagnose the boxwoods.
Please read through our page on boxwood blight--the behavior of dead/dying leaves is very specific and the stem cankers are also a good diagnostic tool: https://extension.umd.edu/hgic/topics/boxwood-blight:
If you do not see that kind of defoliation or cankers given in the link above, you're probably seeing a different disease.
Here is our page with other possible disease problems: https://extension.umd.edu/hgic/topics/boxwood-culture-and-diseases-including-boxwood-blight
Yes, in your situation with such an extensive boxwood planting, the propiconizole would be very effective.
You'll read in the links above that introducing any new boxwood into your planting is risky now. Also beware of pachysandra or sweetbox.