Chinese elm, black spots on leaves


I acquired this elm from a greenhouse late last summer. It had about ten leaves when I got it. It responded well. I wintered it in non-heated greenhouse. We had a really mild winter so I treated everything with mancozeb in early spring.

Unfortunately, these black spots are taking over but I don’t think it’s Anthracnose.

Any ideas? Do I need to prune all infected leaves?

Thank you.

Can you rub the black spots off? If so, can you get a look at them with a magnifying glass. Actually looks like a type of scale, but hard to say from the pic without a closer look. If that’s the case I’d say remove infected leaves then treat.

No, I can’t scrape it off. It’s like tar on the leaves. Here is a closer picture.

Ewww! Sorry, but I’m no help with that. Should probably still remove the leaves that are affected to try to at least slow the spread. Hopefully someone who has seen that before will chime in. The closeup pic will probably help. Good luck.

Thanks for the advice. I pruned all infected leaves. We’ll see what happens.

Update. I defoliated the tree, treated it with Malathion (since I had already treated with Mancozeb in the Spring), and put it my recovery area in dappled light under the maples. The poor tree had about 5 leaves left. But…

Thanks for your advice.

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Yea! Love a happy ending!

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