Diseased lilac -- witches broom?

Asked May 18, 2020, 4:50 PM EDT

Hi there, I've noticed that one of my lilacs has been showing signs of distress. Odd-shaped, blighted leaves. Could this be Witches Broom or something else? Is there any treatment, and if not, if I remove the shrub, is it safe to replant another there?

Kent County Michigan

5 Responses

Greetings! 1) Looks like you have some frost injury like many in Kent County. Photo #2 looks a little suspicious to me, however and I wondered if any weed-and-feed had been used in the lawn or bed area? Also, the scorching on leaves in the first photo looks a bit like chemical burn as well. Can you provide me with more info about this plant so we can make a more accurate diagnosis?

Hi Rebecca, I first noticed it at the end of the summer last year and trimmed some of the affected areas back. I haven't done any treatment to my lawn or surrounding area/ plants in years. My other lilac (on the south side) is just fine. This one is on the north side of my porch. Please let me know if you'd like any other information. I appreciate your help.

Looks like this lilac might have a bacterial plant disease called lilac blight. Last year, we had a cool, wet, rainy, spring season which favors development of lilac blight, especially if rains follow a late frost or winter injury. And this spring isn't much different. Below you will find a tip sheet from our diagnostic lab that will explain in further detail. You can compare more photos by doing a search on line. PS- remember to disenfect your pruning shears in between each cut, so as not to spread into healthy tissue. https://www.canr.msu.edu/news/bacterial_blight_of_lilac

I cut back the affected areas, but noticed this scale. Is this oystershell scale or blight? If it is oystershell scale, what it the best treatment?

Yes, this looks like oyster shell scale. https://www.canr.msu.edu/resources/oystershell_scale Effective time for control is when spirea is blooming, which should be very soon. https://www.canr.msu.edu/news/using_horticultural_oils_on_landscape_plants