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Lilac blight #877973

Asked July 19, 2024, 6:44 PM EDT

100 year old lilacs have blight. Leaves look burnt and falling off. Articles say prune and burn but that would pretty much destroy the bushes. Options? What do I do with leaves? Is compost ok? Should I "scrub" ground below to remove leaves? Would hate to lose them as 15' tall with great gnarly trunks.

Ramsey County Minnesota

Expert Response

I'm not sure what blight or what article you are referring to. Lilacs get a number of diseases, which vary from nuisance to deadly. So you should be certain of your diagnosis. Without photos, I can't help.  Here are a couple of diagnostic sites:
https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/lilac/
https://yardandgarden.extension.iastate.edu/article/2021/08/summer-foliar-lilac-diseases

And here is a link to the plant disease clinic:
https://pdc.umn.edu/submit-sample
Dennis in St. Louis Park Replied July 20, 2024, 4:46 PM EDT
Thanks for responding. I am attaching photos. Today I noticed the bark has a fungus like covering on some branches.



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From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>>
Sent: Saturday, July 20, 2024 3:46:52 PM
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Subject: Re: Lilac blight (#0147891)
 
The Question Asker Replied July 20, 2024, 6:07 PM EDT
The fungus looks like lichen, which I would expect to see on a 100 year old lilac.  Sorry, but the "blight" I can't identify.  There are a lot of lilacs suffering from the excessive moisture this year and there are a number of diseases.  The only way to tell what yours has so you can treat it properly is a lab test. I suggest you send a sample to the plant disease clinic (link in my first post). The disease might be pseudocercospora (which is mentioned in one of the links in my first post):
https://yardandgarden.extension.iastate.edu/encyclopedia/lilac-pseudocercospora-leaf-spot

If you want to avoid the lab test, then clean up fallen leaves and wait and see.
Dennis in St. Louis Park Replied July 21, 2024, 4:39 PM EDT
Thanks. I will get it tested.

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From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>>
Sent: Sunday, July 21, 2024 3:39:56 PM
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Subject: Re: Lilac blight (#0147891)
 
The Question Asker Replied July 21, 2024, 7:26 PM EDT

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