Viburnum Help Please - Ask Extension
Hello - I hope you can help me identify a treatment to save my 13 year old viburnums planted in Mt. Airy MD that have branches of leaves turning brown...
Knowledgebase
Viburnum Help Please #710149
Asked August 06, 2020, 10:36 AM EDT
Hello - I hope you can help me identify a treatment to save my 13 year old viburnums planted in Mt. Airy MD that have branches of leaves turning brown and dropping off, after the leaves drop the branches seem to be dying off. I have examined the plant and did not notice any obvious signs of mildew or insects. I have attached some photos for your reference and would be happy to send more photos if you require them. Thank You in advance for your expert help. John
Carroll County Maryland
Expert Response
Hello John,
This looks like classic damage from a fungal canker disease called Botryosphaeria. Fungicides are not effective but you can trim out all affected branches; look for stems girdled with canker (as in the photo on the page below) and prune below this point into healthy wood. Although this may leave some emptier patches in the branches for awhile, a positive benefit is that the increased air circulation in the shrub's interior may help avoid other issues by promoting faster drying, at least until the growth is gradually replaced. Although the page linked below mentions Rhododendron, this disease affects Viburnum and an array of other shrubs; the mention of partial shade is a bit more Rhododendron-specific, but it can benefit Viburnums as well. Moving a plant this large to a shadier site is impractical, but being aware that full sun can tax their moisture reserves can help you monitor for drought stress in the future.
https://extension.umd.edu/hgic/topics/botryosphaeria-canker-shrubs
Doublefile Viburnums like this one benefit from even soil moisture - they do not prosper in drought and such stresses can make them more vulnerable targets for canker diseases. Occasional irrigation during hot, dry spells would help to preserve their health.
https://extension.umd.edu/hgic/topics/watering-trees-and-shrubs
Miri
This looks like classic damage from a fungal canker disease called Botryosphaeria. Fungicides are not effective but you can trim out all affected branches; look for stems girdled with canker (as in the photo on the page below) and prune below this point into healthy wood. Although this may leave some emptier patches in the branches for awhile, a positive benefit is that the increased air circulation in the shrub's interior may help avoid other issues by promoting faster drying, at least until the growth is gradually replaced. Although the page linked below mentions Rhododendron, this disease affects Viburnum and an array of other shrubs; the mention of partial shade is a bit more Rhododendron-specific, but it can benefit Viburnums as well. Moving a plant this large to a shadier site is impractical, but being aware that full sun can tax their moisture reserves can help you monitor for drought stress in the future.
https://extension.umd.edu/hgic/topics/botryosphaeria-canker-shrubs
Doublefile Viburnums like this one benefit from even soil moisture - they do not prosper in drought and such stresses can make them more vulnerable targets for canker diseases. Occasional irrigation during hot, dry spells would help to preserve their health.
https://extension.umd.edu/hgic/topics/watering-trees-and-shrubs
Miri
Miri,
Thank you very much for the thorough response. I have followed your instructions and trimmed out the affected branches with the hope that this will promote new growth.
When cutting out the affected branches I noticed the cross section showed large brown areas in the cross section which made me think there was also a bug or systemic problem. I have included photos for your reference. I was wondering if I should also treat the shrubs by watering with a solution of water and BioAdvanced 3 in 1 Insect, disease and mite control to prevent / cure additional issues that might be causing the brown spots on the cross section. Thank You John
Thank you very much for the thorough response. I have followed your instructions and trimmed out the affected branches with the hope that this will promote new growth.
When cutting out the affected branches I noticed the cross section showed large brown areas in the cross section which made me think there was also a bug or systemic problem. I have included photos for your reference. I was wondering if I should also treat the shrubs by watering with a solution of water and BioAdvanced 3 in 1 Insect, disease and mite control to prevent / cure additional issues that might be causing the brown spots on the cross section. Thank You John
This is likely still due to the Botryosphaeria, so trim that stem down even lower (as you can, given the branch crowding at the base). Using a fungicide (including that product) will not help as the fungus is already in the tissues - they work preventatively and are not curative. Physical removal of diseased tissues are more practical and effective here than using a fungicide. Viburnums can sucker from the roots, so if a few main major branches end up dying from Botryosphaeria, new growth still could replace it, even though that growth will take several years to mature.
Miri
Miri
