Our wet spring has caused a few problems this year. We are getting a lot of questions about possible lilac blight.

There are two kinds of blight: Bacterial blight pseudomonas syringae pv.syringae and Ascochyta blight ascochyta syringae.

I can’t say for sure what kind of blight you have but the treatment is the same. There is nothing to be done this year to treat your shrubs but clean up throughout the summer and into the fall is essential.

The effect is mostly cosmetic and will not kill your lilacs unless they suffer for several successive years.

You can send the pruned branches to your local compost. Do not compost them at home as a small home pile will not get hot enough to kill the pathogens.

https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/lilac/leavesblotches.html

https://extension.oregonstate.edu/news/how-recognize-treat-avoid-lilac-bacterial-blight