Shrubs - Ask Extension
These plants appear to be dying? what might the problem be and what if anything can be done to save them. Thank you for your help.
Knowledgebase
Shrubs #864607
Asked April 15, 2024, 2:23 PM EDT
These plants appear to be dying? what might the problem be and what if anything can be done to save them. Thank you for your help.
Lane County Oregon
Expert Response
Thank you Mike for your question to "Ask Extension". There are many causes for leaf discoloration and defoliation in boxwoods. The worst case scenario is boxwood blight. The symptoms of boxwood blight include dark or light brown spots on leaves, often in a circular or zonate pattern, black streaks or cankers on stems, straw-to bronze-colored or grayish-black blighted foliage, and defoliation. A yellow or orange halo around leaf spots may also be observed. Leaf spots can grow together to cover the entire leaf surface. Downy white fungal growth may be seen on the underside of leaves. Tufts of white spores (sporodochia) may be seen along lesions. I am unable to tell from your photos if your plants have any of these symptoms.
Boxwood blight can be a challenging disease to identify outside a plant diagnostic laboratory. I'll repeat, conformation of this disease must be conducted by a plant diagnostic laboratory.
I have provided you with a link to a website that gives directions for providing a sample to the OSU plant disease diagnostic laboratory. There is a fee associated with each sample.
https://bpp.oregonstate.edu/how-submit-plant-materials
Many of the symptoms associated with the disease are similar to other common boxwood disorders. One major difference between boxwood blight and its look-alikes is the potential for defoliation. Boxwood blight causes extensive defoliation, while look-alike disorders tend to have leaves turn tan to brown, but remain attached to the plant. A microscope is needed to confirm the disease diagnosis. Some of the common boxwood blight look-alikes include winter Injury, Macrophoma leaf spot, Volutella blight, Phytophthora root rot, these look-alikes cause a relatively minor injury that can be pruned out during a dry period of spring weather.
I recommend to prune your plants when they are dry and disinfect pruning equipment, especially between plants. Disinfect with isopropyl alcohol or a dilute bleach solution. Do not compost leaves. Place all plant material in plastic bags and discard in the land fill.
I hope that you find this information useful and as always Happy Gardening. If you have any additional questions please feel free to respond.
Boxwood blight can be a challenging disease to identify outside a plant diagnostic laboratory. I'll repeat, conformation of this disease must be conducted by a plant diagnostic laboratory.
I have provided you with a link to a website that gives directions for providing a sample to the OSU plant disease diagnostic laboratory. There is a fee associated with each sample.
https://bpp.oregonstate.edu/how-submit-plant-materials
Many of the symptoms associated with the disease are similar to other common boxwood disorders. One major difference between boxwood blight and its look-alikes is the potential for defoliation. Boxwood blight causes extensive defoliation, while look-alike disorders tend to have leaves turn tan to brown, but remain attached to the plant. A microscope is needed to confirm the disease diagnosis. Some of the common boxwood blight look-alikes include winter Injury, Macrophoma leaf spot, Volutella blight, Phytophthora root rot, these look-alikes cause a relatively minor injury that can be pruned out during a dry period of spring weather.
I recommend to prune your plants when they are dry and disinfect pruning equipment, especially between plants. Disinfect with isopropyl alcohol or a dilute bleach solution. Do not compost leaves. Place all plant material in plastic bags and discard in the land fill.
I hope that you find this information useful and as always Happy Gardening. If you have any additional questions please feel free to respond.
