10 yr old lilacs dying - Ask Extension
Our lilac bushes are 10 feet tall and look like they are dying. They are at least 10 yrs old. How can I save them? Brown leaves and dry. We’ve be...
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10 yr old lilacs dying #880098
Asked August 04, 2024, 9:07 AM EDT
Our lilac bushes are 10 feet tall and look like they are dying. They are at least 10 yrs old. How can I save them? Brown leaves and dry. We’ve been watering during no rain and heat.
Eaton County Michigan
Expert Response
There are a few reasons for lilac leaves turning brown. One common one is leaf scorch. Many lilacs are experiencing leaf scorch this year. Saturated soils caused by excessive rains can effectively suffocate and kill portions of the root system. Once the hot, dry summer weather arrives, the plant doesn't have a root system
capable of supporting the vegetation. Leaves will often quickly dry up and remain suspended on the plant.
Another possibility is lilac blight. Lilac blight is extremely common. This disease could be caused by a bacterium Pseudomonas syringae which has leaf darkening, leaf wilting, and leaf dropping. This is largely a cosmetic condition and unless it occurs for several years has no adverse effects. It is associated with wet conditions, as during this summer. This is NOT a fungus; fungicides are of no use. It can be transmitted from one season to the next via leaf debris. Thus, to prevent transmission thorough fall cleanup is essential. See here for
information:
https://extension.umn.edu/plant-diseases/leaf-spot-diseases-trees-and-shrubs#bacterial-leaf-spots-and-blight-1156513
https://yardandgarden.extension.iastate.edu/encyclopedia/lilac-bacterialblight#:~:text=Symptoms%20of%20lilac%20bacterial%20blight,Eventually%2C%20leaves%20may%20be%20killed.
It could be caused by Cercospora or Septoria fungi. The symptoms are small, brown to black spots appearing on lilac leaves that are surrounded by a yellow halo. The leaves will become distorted and drop prematurely. See
https://yardandgarden.extension.iastate.edu/article/2021/08/summer-foliar-lilac-diseases
It is not important which type of blight it is; it should not kill your lilacs. Do not feel that they must be dug up immediately and discarded. They will recover although their blooming may be delayed by a season or two.
There is not much you can do to make your lilacs look normal. The most important thing to do now is to rake up and destroy the fallen infected leaves. This will help prevent the disease from overwintering and re-infecting your lilac next year. Besides cleaning up and removing all leaf debris, some pruning should be done. Many lilacs have not had proper pruning for several years and need some rejuvenation pruning. Here's how to do this:
a) Remove dead wood and volunteer trees and bushes.
b) Cut off 1/3 of the largest stems (approximately up to a third of the plant) just above ground level. The objective is to improve air
movement and circulation throughout the bush. This will help in
decreasing the spread of the disease.
c) Repeat b) for two years. Allow the smaller shoots to grow up, essentially creating an all new lilac.
https://holdenfg.org/blog/rejuvenation-pruning-of-lilac-bushes/
Destroy all plant debris. Do not compost.
Pruning is critical to reducing disease opportunities in multi-stemmed shrubs like lilac. Rejuvenation pruning and can be done annually or every few years. It will open up the shrub, promote better airflow, and give younger growth the room to develop and put on a great flower show.
capable of supporting the vegetation. Leaves will often quickly dry up and remain suspended on the plant.
Another possibility is lilac blight. Lilac blight is extremely common. This disease could be caused by a bacterium Pseudomonas syringae which has leaf darkening, leaf wilting, and leaf dropping. This is largely a cosmetic condition and unless it occurs for several years has no adverse effects. It is associated with wet conditions, as during this summer. This is NOT a fungus; fungicides are of no use. It can be transmitted from one season to the next via leaf debris. Thus, to prevent transmission thorough fall cleanup is essential. See here for
information:
https://extension.umn.edu/plant-diseases/leaf-spot-diseases-trees-and-shrubs#bacterial-leaf-spots-and-blight-1156513
https://yardandgarden.extension.iastate.edu/encyclopedia/lilac-bacterialblight#:~:text=Symptoms%20of%20lilac%20bacterial%20blight,Eventually%2C%20leaves%20may%20be%20killed.
It could be caused by Cercospora or Septoria fungi. The symptoms are small, brown to black spots appearing on lilac leaves that are surrounded by a yellow halo. The leaves will become distorted and drop prematurely. See
https://yardandgarden.extension.iastate.edu/article/2021/08/summer-foliar-lilac-diseases
It is not important which type of blight it is; it should not kill your lilacs. Do not feel that they must be dug up immediately and discarded. They will recover although their blooming may be delayed by a season or two.
There is not much you can do to make your lilacs look normal. The most important thing to do now is to rake up and destroy the fallen infected leaves. This will help prevent the disease from overwintering and re-infecting your lilac next year. Besides cleaning up and removing all leaf debris, some pruning should be done. Many lilacs have not had proper pruning for several years and need some rejuvenation pruning. Here's how to do this:
a) Remove dead wood and volunteer trees and bushes.
b) Cut off 1/3 of the largest stems (approximately up to a third of the plant) just above ground level. The objective is to improve air
movement and circulation throughout the bush. This will help in
decreasing the spread of the disease.
c) Repeat b) for two years. Allow the smaller shoots to grow up, essentially creating an all new lilac.
https://holdenfg.org/blog/rejuvenation-pruning-of-lilac-bushes/
Destroy all plant debris. Do not compost.
Pruning is critical to reducing disease opportunities in multi-stemmed shrubs like lilac. Rejuvenation pruning and can be done annually or every few years. It will open up the shrub, promote better airflow, and give younger growth the room to develop and put on a great flower show.
