Why are Lilac leaves curling? - Ask Extension
I have an established Lilac in my front lawn, whose leaves are curling. General observations:
1. Soil moisture level is good (checked with a moistu...
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Why are Lilac leaves curling? #867565
Asked May 08, 2024, 12:30 PM EDT
I have an established Lilac in my front lawn, whose leaves are curling. General observations:
1. Soil moisture level is good (checked with a moisture sensor and it has been raining in Portland Oregon for weeks now).
2. Checked leaves for aphids-no real signs of it.
3. There are no dark spots or powdery mildew on leaves. Attached is a picture of it.
So, what is causing the curling and how do I fix it? I am planning on pruning it in the next few weeks and looking for ways to fix it.
Washington County Oregon
Expert Response
Thank you for your question. Clear photos of the stems, to see if there are brown spots would be helpful to diagnose the problem. But I suspect that your plant has a bacterial infection described here: https://pnwhandbooks.org/plantdisease/host-disease/lilac-syringa-spp-bacterial-blights
As you can read, pruning off the deformed leaves, pruning the entire plant for more air circulation, and protecting the plant from rain and frost in the spring may help in the future. Since lilacs have 7 other known diseases (all of which have different symptoms than your plant), you can also submit plant samples to the OSU Plant Clinic for diagnosis: https://bpp.oregonstate.edu/how-submit-plant-materials
Good luck!
As you can read, pruning off the deformed leaves, pruning the entire plant for more air circulation, and protecting the plant from rain and frost in the spring may help in the future. Since lilacs have 7 other known diseases (all of which have different symptoms than your plant), you can also submit plant samples to the OSU Plant Clinic for diagnosis: https://bpp.oregonstate.edu/how-submit-plant-materials
Good luck!
I found the culprit. While pruning I found the stem hallowed out and some larva in it. Given the infestation I am planning on removing the plant. So 2 question;
1. I have azaleas next to the lilac. Do I need to worry about them?
2. Any suggestions for replacement plants that are not prone to the borer?
thanks
So sorry! Here are the plants the lilac/ash borer infests: "Lilac (Syringa spp.), ash (Fraxinus spp.), mountain ash (Sorbus) and privet (Ligustrum spp.) are the preferred hosts but other members of the olive family (Oleaceae) may also serve as occasional hosts." https://ag.umass.edu/landscape/fact-sheets/lilac-borer-also-known-ash-borer
I would suggest that you read the following, which has ideas for native plants not susceptible to this pest: https://extension.oregonstate.edu/catalog/pub/ec-1577-gardening-oregon-native-plants-west-cascades
Good luck!
I would suggest that you read the following, which has ideas for native plants not susceptible to this pest: https://extension.oregonstate.edu/catalog/pub/ec-1577-gardening-oregon-native-plants-west-cascades
Good luck!
