lilacs turning brown -- how to respond or remove?

Question: Hello, my lilac bushes are suffering from a terrible blight or fungus that is causing most of the leaves to turn brown and shrivel up (see pics).  I've noticed the same thing happening to other lilacs in the neighborhood.  I remember this happening a few years ago (four or five maybe?), but the lilacs did fine in subsequent years.  

I am thinking about removing the lilacs but am not sure how.  Do people have to use bobcats or something like that to pull them out of the ground?  And if I do that, can I take them to the community compost facility without spreading whatever this is?  If I can't remove them, is there something I can do to make this less likely to happen next year?

responder: Maureen Graber  Replied August 04, 2024, 9:35 AM EDT
response: Good Morning Barbara,  Thank you for contacting the U of M Extension Service.  Your lilac is experiencing a blight condition. This is now extremely common in the Metro area. Some comments: 1). It could be a blight caused by the bacterium Pseudomonas syringae. Among other things, it is characterized by leaf spots that can lead to leaf darkening, leaf wilting, and premature leaf dropping. Fortunately, this is largely a cosmetic condition and unless it occurs over several seasons, there are no adverse effects. It is associated with wet conditions, which certainly describes our current 2024 season. Because this is NOT a fungal pathogen, application of fungicides will do no good. It can be transmitted from one season to the next via leaf debris. To prevent transmission from one season to the next, thorough fall cleanup is essential. See the following for further information and remedial procedures: 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-bacterial-blight - :~:text=Management of lilac bacterial blight&text=Select varieties that have tolerance,bleach solution between each cut. http://plantclinic.cornell.edu/factsheets/lilacbacterialblight.pdf https://hort.extension.wisc.edu/articles/bacterial-blight/ https://extension.oregonstate.edu/news/how-recognize-treat-avoid-lilac-bacterial-blight 2). It could be a blight caused by either Cercospora or Septoria fungi. The symptoms are small, brown to black spots appearing on lilac leaves. The distinguishing feature of these spots is that they are surrounded by a yellow halo. Inspect your lilac leaves to see if this halo is present. The leaves will also become distorted and drop prematurely. See: https://extension.missouri.edu/media/wysiwyg/Extensiondata/Pro/PlantDiagnosticClinic/Docs/leaf-spot-on-lilac.pdf https://yardandgarden.extension.iastate.edu/article/2021/08/summer-foliar-lilac-diseases 3). It really is not important which type of blight exists; it should not be a fatal situation for 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. However if you are curious as to which type of blight exists, consider submitting plant samples to a diagnostic disease laboratory for an analysis. This would be a definitive way of getting to the bottom of things. Both Wisconsin and Minnesota have excellent labs to do this. Before submitting anything to either of them, call first as to what type of samples should be submitted. Both have a nominal charge for their analysis. See https://pdc.umn.edu/ https://pddc.wisc.edu/clinic-overview/ 4). There is not much you can presently do to make your lilacs attain a normal appearance. Your efforts must be more proactive, thinking ahead to the 2025 season to prevent a recurrence of this blight. Besides cleaning up and removing all leaf debris at this time (August 2024), you could cut out a few stems to open things up. Do this cutting 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. 5). The sites previously mentioned will describe further proactive approaches. In short, they are: a). Remove and destroy infected plant parts, including fallen leaves and pruned branches, to reduce further spread of the bacteria or fungus. Lilacs are tough; they should withstand this removal. b). Prune the lilacs to improve air circulation and remove diseased branches. Make cuts well below the visible symptoms and disinfect (solution of one part commercial bleach to nine parts water) pruning tools between cuts. c). Avoid overhead watering to minimize leaf wetness and reduce the spread of bacteria. Water at the base of the plants. d). Going into the fall, keep your lilacs well-watered and be sure to do a thorough cleanup of all plant debris. It is not necessary to remove the lilacs. This is a link to renewal pruning of lilacs and rejuvination pruning; https://extension.umn.edu/planting-and-growing-guides/pruning-trees-and-shrubs#hedges-and-shrubs-1336763 Yes, the debris can go to the community compost site.  Good Luck!

responder: The Question Asker Replied August 04, 2024, 2:47 PM EDT
response: Thank you so much!  I really appreciate the information and will do my best to do the necessary pruning and cleaning up.  This is a great service.   --Barbara   From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask ExtensionSent: Sunday, August 4, 2024 8:35 AMTo: Barbara Freese <<personal data hidden>>Subject: Re: lilacs turning brown -- how to respond or remove? (#0149837)

responder: Maureen Graber  Replied August 06, 2024, 8:10 PM EDT
response: You are welcome!