Hi Katherine,

Many lilacs are getting bacterial blight this year. Here's some helpful web pages:

https://yardandgarden.extension.iastate.edu/encyclopedia/lilac-bacterial-blight

http://plantclinic.cornell.edu/factsheets/lilacbacterialblight.pdf

If you don't think this is blight, this page may help you narrow the cause:

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

The only way to determine if this is blight is to have a sample of the plant tested. The Plant Disease Clinic at the U of M does this, but for a price. You can find more information here:

https://pdc.umn.edu/

Both of the links above suggest ways to manage the disease, including raking up and disposing of fallen leaves and pruning to open up the plants and allow better air circulation.

Good luck.

My lilacs in this area were damaged by reroofing my home last Fall.  Also, the amount of watering this Spring/Summer is not in my control.

Given that I will not be using any chemicals, is the best option to pull out the diseased lilacs so this does not spread?

Hi, 

That’s up to you. Without a sure diagnosis, which will come only through an expensive test, I can’t make a recommendation beyond what’s in the above websites.

This blight is all over Minnesota this year. I’m not sure leaving your lilacs alone will contribute to spread. But you should do what you’re comfortable with.

Thanks.