Lilac Bushes
Q.

Should I prune lilac branches that have leaf blight in the fall, or wait until spring?

Zone 19301 | Anonymous added on October 22, 2019 | Answered

I have a large Korean lilac bush, which I pruned some this summer. It had produced very few blooms and had become overgrown. About mid-October I noticed that the leaves were turning brown, curling up and falling off. By the end of October all the leaves are on the ground. It looks like leaf blight and I read that I should prune 6 inches below the infected branches. It is hard to tell where the infection is (maybe it's not leaf blight). Should I just remove the leaves and wait until spring to prune or do it now (late Oct)? Is there some other disease which would cause this?

A.
A.Answers to this queston: Add Answer
GKH_Susan
Certified GKH Gardening Expert
Answered on October 23, 2019

It may be bacterial leaf blight. You can get a definitive diagnosis by contacting the cooperative extension office near you.

Since the leaves have dropped, be sure to remove them and discard in the trash. In the spring, if new shoots turn black and droop, prune the branch back several inches above the infected area.
Here is more information about blight management.

https://hortnews.extension.iastate.edu/lilac-bacterial-blight

https://www.gardeningknowhow.com/ornamental/shrubs/lilac/common-lilac-problems.htm

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