Boxwood Blight?

Asked October 23, 2016, 11:42 AM EDT

22 Dwarf English boxwoods were planted in my yard 14 months ago. Several of them are showing signs of serious health issues that have led them to die off or partially die. Is this boxwood blight? If so, are all infected and it's a matter of time until they all die off? Or can the seemingly healthy looking ones be saved and I just replace the affected ones? Please advise what I need to do, e.g. treat the soil and neighboring plants, remove everything, etc. Thanks!

Montgomery County Maryland

3 Responses

Boxwoods in general can be susceptible to several fungal diseases, insect, and abiotoc issues (cultural and environmental). If stressed by poor site conditions such as drought, poor drainage, poor planting techniques, over mulching, etc. it is not uncommon for them to be susceptible to possible insect and disease problems. In general when plants decline within the first year or two it can be attributed to lack of establishment and the above issues. See more on our publications http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG86%20Common%20Abio...
http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG52_IPM_Boxwood.pdf

Boxwood blight, is a relatively new disease and may be a possibility, if new boxwoods have been introduced into your landscape. Monitor your plants for signs and symptoms such as stem cankers and defoliation. See the attached link for photos and more information http://extension.umd.edu/hgic/invasives/boxwood-blight

Our plant pathologist is out of the office until October 3lst. We will show him your photos and send additional information regarding your boxwood.
mh

Would it help if I brought some trimmings? I've attached additional photos to show the pathologist. Thank you

We showed your photos to our plant pathologist. This does not look like boxwood blight symptoms as there is no defoliation. The yellowing looks like a root problem and overall failure to establish.due to several reasons.
When a plant fails to establish you will have to look at your watering routine, site conditions, and planting techniques. Also, look for vole damage. A type of meadow mouse that feeds on the root of trees and shrubs. http://extension.umd.edu/hgic/voles
See our website for more information on planting trees and shrubs and look at the planting process and care.http://extension.umd.edu/hgic/trees-and-shrubs/concept-planting-maintenance
Do not plant too deeply.
If you added amended soil to the planting hole, this can create a bathtub effect and the roots tend not to grow out of the enriched soil into the native soil. Also, Plants often “drown” in these holes because organic matter holds water like a sponge, while the surrounding clayey soil is slow to drain.
Make sure the rootball is accepting water. When the rootball is dry it can actually shed water. Probe with a screwdriver and make sure the root ball is moist. Water deeply to penetrate to the bottom of the rootball. When the top several inches dry out. Water again. You will have to water up until the ground freezes. Check the soil moisture weekly. Do not overwater.

You did not mention if the shrubs were in containers. If so, sometimes container shrubs can become rootbound in the container. Container plants establish faster if you disturb the “around the pot” growth direction of the roots. Use a sharp knife or blade to cut four one-inch-deep cuts the length of the root ball. New roots will rapidly grow from the cut areas of the roots.
See our website for planting and post planting care.
At this point, all you can do is remove dead plants and prune dead branches. Keep the plants well watered up until the ground freezes. Make sure mulch is no thicker than several inches and away from the base of the plants. Also, look at the above boxwood publication for more information.
mh