Sick Lilac - Ask Extension
Lilac hedge has turned brown seemingly overnight. There has been ample rain. Is it diseased? Will it recover next year?
Knowledgebase
Sick Lilac #880144
Asked August 04, 2024, 2:12 PM EDT
Lilac hedge has turned brown seemingly overnight. There has been ample rain. Is it diseased? Will it recover next year?
Chittenden County Vermont
Expert Response
Dear Carol:
Thank you for contacting the UVM Master Gardener Helpline about your lilac and providing photos. We have received similar questions from people throughout the state whose lilacs are exhibiting the same symptoms.
The UVM Extension's plant pathologist notes that pseudocercospora-leaf-spot is a fungal leafspot common in lilacs especially in rainy years. The fungus is able to survive two years in the plant debris that is scattered on the ground. The best and easiest strategy to reduce the disease is to rake and destroy leaves in the fall and prune to open up the bush to air and light. Fungicides are rarely warranted because buds are all set for next year. See the factsheet in the following link: https://yardandgarden.extension.iastate.edu/article/2021/08/summer-foliar-lilac-diseases
We attach links to additional articles that you may find helpful: “What’s wrong with my lilac? Summer Foliar diseases on lilac” published by the University of Illinois Extension:
https://extension.illinois.edu/blogs/good-growing/2021-08-05-whats-wrong-my-lilac-summer-foliar-diseases-lilac which explains the importance of consistently pruning your shrub.
“Leaf Spot on Lilac” published by the University of Missouri Extension: https://extension.missouri.edu/media/wysiwyg/Extensiondata/Pro/PlantDiagnosticClinic/Docs/leaf-spot-on-lilac.pdf which includes information about managing the disease.
The University of Maine Extension offers this article “Bulletin #2169, Pruning Woody Landscape Plants” from the University of Maine Extension that has a link to their video on pruning a lilac: https://extension.umaine.edu/publications/2169e/
We also attach an excellent general resource for reference: https://extension.umn.edu/trees-and-shrubs/lilacs
We hope that this information is helpful. Although the leaves are unsightly, rarely will the fungal leaf spot become severe enough to cause the decline of the plant especially if you practice good sanitation by removing and destroying leaf debris and pruning out dead branches.
Regards,
Pat
Thank you for contacting the UVM Master Gardener Helpline about your lilac and providing photos. We have received similar questions from people throughout the state whose lilacs are exhibiting the same symptoms.
The UVM Extension's plant pathologist notes that pseudocercospora-leaf-spot is a fungal leafspot common in lilacs especially in rainy years. The fungus is able to survive two years in the plant debris that is scattered on the ground. The best and easiest strategy to reduce the disease is to rake and destroy leaves in the fall and prune to open up the bush to air and light. Fungicides are rarely warranted because buds are all set for next year. See the factsheet in the following link: https://yardandgarden.extension.iastate.edu/article/2021/08/summer-foliar-lilac-diseases
We attach links to additional articles that you may find helpful: “What’s wrong with my lilac? Summer Foliar diseases on lilac” published by the University of Illinois Extension:
https://extension.illinois.edu/blogs/good-growing/2021-08-05-whats-wrong-my-lilac-summer-foliar-diseases-lilac which explains the importance of consistently pruning your shrub.
“Leaf Spot on Lilac” published by the University of Missouri Extension: https://extension.missouri.edu/media/wysiwyg/Extensiondata/Pro/PlantDiagnosticClinic/Docs/leaf-spot-on-lilac.pdf which includes information about managing the disease.
The University of Maine Extension offers this article “Bulletin #2169, Pruning Woody Landscape Plants” from the University of Maine Extension that has a link to their video on pruning a lilac: https://extension.umaine.edu/publications/2169e/
We also attach an excellent general resource for reference: https://extension.umn.edu/trees-and-shrubs/lilacs
We hope that this information is helpful. Although the leaves are unsightly, rarely will the fungal leaf spot become severe enough to cause the decline of the plant especially if you practice good sanitation by removing and destroying leaf debris and pruning out dead branches.
Regards,
Pat
