What is this on our leaves? - Ask Extension
Hello,
At the beginning of leafing out this year some of the leaves on our trees had some black spotting. We've had two different opinions on whethe...
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What is this on our leaves? #921376
Asked November 04, 2025, 11:40 AM EST
Hello,
At the beginning of leafing out this year some of the leaves on our trees had some black spotting. We've had two different opinions on whether there is a problem. We usually use these leaves as mulch on our planting beds and would like to know:
1. Do our trees have a problem?
2. Can we mulch these leaves for our planting beds?
I have attached a photo.
Thank you!!
craig
Multnomah County Oregon
Expert Response
Hi Craig and thanks for your question about using your leaves. This looks like a classic case of anthracnose (see attached article). As you will see, you should not use the leaves in compost or as mulch. They should be trashed or burned if possible.
Other controls listed are:
Sorry it's not better news,
Other controls listed are:
- Rake up and destroy fallen leaves.
- Remove and destroy twig cankers during dormant pruning.
- Time irrigation to minimize the time leaves are wet.
Of course we can't control the timing of the rain, but there is one product recommended for home use to spray next spring:
Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water.
https://pnwhandbooks.org/plantdisease/host-disease/maple-acer-spp-anthracnoseSorry it's not better news,
Hello,
We typically use our blower as a vacuum and vacuum up the leaves. But the leaves go through blades inside the vacuum before going into the bag. Can we still gather the leaves this way? Or is it possible that some of the fungus can make it out and spread the fungus?
Thank you!
craig
From: ask=<personal data hidden> On Behalf Of Ask Extension
Sent: Tuesday, November 4, 2025 9:32 AM
To: Craig Cedros
Subject: Re: What is this on our leaves? (#0191292)
Hi Craig- The fungus is in the soil and air anyway, so it won't matter if you use the blower to capture the leaves. If you use it for other leaves that you want to mulch, you might run some good leaves through it first to "clean it" out.
Many maple trees are having this same problem. It is often acerbated by weather events. Hopefully the tree will be able to recover.
Many maple trees are having this same problem. It is often acerbated by weather events. Hopefully the tree will be able to recover.
