Lilac leaves curling

Question: The leaves on my two 6’x6’ French lilac bushes are curling upward, no insects are visible, even when I looked with magnifying glass. It bloomed well, but has gotten worse since blooming. We have had a lot of rain and also significant hail.  There are also brown edges, but no trails from insects that I could see. Could it be from a herbicide drift? I am attaching pictures.

responder: An Ask Extension Expert Replied June 26, 2023, 7:32 PM EDT
response: Hello Eileen, Thank you for your inquiry. I'm sorry to see the issue your lilacs are experiencing. Was any herbicide used on the turf near the lilacs? If so, what herbicide was used? Does the other side of the lilac that is away from the turf show the same cupping of the leaves? Thank you, Allisa LinfieldHorticulture Program CoordinatorCSU Extension El Paso County

responder: The Question Asker Replied June 26, 2023, 8:45 PM EDT
response: Dear Allisa,Thank you for your quick response. The curled leaves seem to be around all sides of the lilac bushes.  A granular weed and feed was applied to the lawn on the west side of the lilac bushes in early spring on March 24 by Integrated Lawn Care. On April 1, they applied a liquid weed killer to the 1-3” river rocks around the edge of  our lawn which includes around the base of the lilac bushes. None of our other shrubbery show any damage, however, and all of them also have the rocks around them that were sprayed. I put in a request to Tall Timbers for an arborist to come out to the house and look at the lilac bushes. Do you think this is a good idea? Thank you for any advice you can give.Eileen LevinOn Mon, Jun 26, 2023 at 5:32 PM Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied July 03, 2023, 3:50 PM EDT
response: Hello Eileen, Again, I'm so sorry to see the extensive damage to your lilacs. Most weed-and-feeds contain 2,4-D which kills broadleaf weeds in turf. Lilacs are quite susceptible to damage from this herbicide, which can volatilize and impact trees and shrubs near the turf. Not all trees and shrubs are as sensitive to this herbicide as lilacs. The distortion of the leaves does look like herbicide damage. Are you able to contact Integrated Lawn Care and ask specifically what weed-and-feed was used? Also it would be good to ask what liquid weed killer they used on the river rock. My guess is they used a contact herbicide on the river rock, meaning that the herbicide only kills what it touches. I would be more concerned about the 2,4-D from the weed-and-feed volatilizing and impacting the lilacs. If it is herbicide damage, then I would not worry too much just yet. It is possible, even likely, that it will leaf out normally next year.  I'm not sure that Tall Timbers will be able to provide any kind of treatment, but most arborists don't charge for a site visit, so it doesn't hurt to have them look at it. I'm sorry I don't have a more reassuring answer for you, but I hope this is helpful.  Thank you, Allisa LinfieldHorticulture Program CoordinatorCSU Extension El Paso County

responder: The Question Asker Replied August 12, 2024, 6:05 PM EDT
response: Hi Alissa,I am sorry it took me so long to get back to you.  Neither Sav a tree or Tall Timbers’ arborist could tell me what was wrong with the lilacs. But I did some research online and this is what I think it might be. Maybe you know more about this disease or if there is any way to treat it. They have a drip on them, so Ithink I should remove it if this is what they are suffering from. They have looked better since the weather has been drier. Thanks for your help. If you have any other ideas,please let me know. Eileen Levi https://hortnews.extension.iastate.edu/phytophthora-shoot-blight-lilacsOn Mon, Jul 3, 2023 at 1:50 PM Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied August 28, 2024, 4:52 PM EDT
response: Hello Eileen, Phytophthora is common in the landscape and could potentially impact your lilac. However, the photo you originally sent did not show the characteristic browning and dieback on shoots. Instead, the leaves looked more cupped and curled, which again, is more a sign of herbicide damage. If it was herbicide damage, then it makes sense that the symptoms improved over time as new leaves grew out. At this point in the season, I would just wait and see if you see these symptoms again next year. Unfortunately, if Phytophthora is the culprit, then the only treatment is to remove the plant and avoid planting other susceptible plants in that spot. If it was herbicide damage, then it is likely that the lilac would leaf out without issue next spring, provided that there is not herbicide applied in that area again.  Best, Allisa LinfieldHorticulture CoordinatorCSU Extension El Paso County