Lilac Bush Dying?

Asked September 17, 2016, 7:51 PM EDT

I Have a 4 Year old Common Purple Lilac Bush, It just bloomed this year for the first time, now seeing a stalk with brown leaves & another stalk nearby with yellowing leaves. The third picture is of the green leaves, I am assuming this coloring on the green leaves is mold due to the wet conditions Mother Nature has given us this year,I am not assuming the mold is fatal but I am concerned with the other areas. What can I do to make sure this plant lives a long happy life?

Hennepin County Minnesota

1 Response

Thank you for the question. You are correct about the mold spots-they aren't a big concern and the shrub should tolerate it well. However, the dead brown branch, along with the nearby yellowing branch are suspicious for verticillium wilt. Verticillium is a common soil borne fungus that can be a problem for woody ornamentals like your lilac.
Other causes for what you are seeing could be herbicide damage that may have drifted in, mechanical factors like weed whip or lawn mower injuries, and adverse environmental conditions (too hot, too dry, too wet, etc.). A sign that may may help tip the diagnosis in the direction of verticillium is streaking of the wood. On a branch that has died, peel back the bark and check for streaks. It is risky to make a diagnosis on the basis of photos, so read more about it here:

If it is verticillium wilt, the shrub may recover and experience bouts of recurrence or the disease may move through the plant quickly, killing it. What you can do now is to remove the dead branches and discard in the trash to avoid spreading the diseases. Water well until the ground freezes and mulch around the base of the lilac, keeping the mulch away from the trunk.
You might consider sending a sample to the University Plant Diseases Clinic for definitive diagnosis:

Check out our self-diagnostic program here: Your shrub looks very similar to the lilac examples under the 'dead and dying branches' link.

Good luck with your tree and thank you for contacting Extension.