Black mold on some leaves of magnolia bush

Thank you for writing.
Although you did not send a picture, I am reasonably sure this is sooty mold, explained here. https://extension.unh.edu/blog/2018/07/why-are-leaves-my-magnolia-turning-black-attracting-wasps
The problem is that if it is caused by magnolia scale, this can turn into a very serious problem very quickly.
I would like a close up picture of a couple leaves and a careful search and photograph of magnolia scale.
https://hort.extension.wisc.edu/articles/magnolia-scale/

Steve Miles, Master Gardener, Hennepin County, (I am a volunteer human being: not a bot, not AI). I'm an avid gardener but not a degreed or certified horticulturist or arborist. I will do much better if you also send a photograph. I like follow-up questions. The University' garden soil tests are excellent. https://soiltest.cfans.umn.edu/testing-services/lawn-garden This is how to find a tree expert. https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional A Directory of ISA certified arborists is at https://certificates.directory.isa-arbor.com/ The Minnesota Landscape Arboretum is a wonderful place to see and learn about plants that grow in Minnesota. https://mngardens.horticulture.umn.edu/minnesota-landscape-arboretum Ask a Master Gardener is a public service of the University of MInnesota's Extension Division. Please donate if we make you happy. https://give.umn.edu/gardener Replied August 17, 2026, 4:55 PM EDT

Ugh, you were spot on. Within a day, the shrub was heavily infested with magnolia scale. I pruned a few branches and tried to remove all the scale I could see.

Is there something I should spray on the magnolia shrub now?

Thank you, Laura Anderson

The Question Asker Replied August 18, 2026, 7:31 PM EDT

Sorry to hear that I was correct.
Take a garden hose, turn to the tightest most fierce jet that you can and blast them but do not blast those critters onto other magnolia.
Send me a before and after picture,

Steve Miles, Master Gardener, Hennepin County, (I am a volunteer human being: not a bot, not AI). I'm an avid gardener but not a degreed or certified horticulturist or arborist. I will do much better if you also send a photograph. I like follow-up questions. The University' garden soil tests are excellent. https://soiltest.cfans.umn.edu/testing-services/lawn-garden This is how to find a tree expert. https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional A Directory of ISA certified arborists is at https://certificates.directory.isa-arbor.com/ The Minnesota Landscape Arboretum is a wonderful place to see and learn about plants that grow in Minnesota. https://mngardens.horticulture.umn.edu/minnesota-landscape-arboretum Ask a Master Gardener is a public service of the University of MInnesota's Extension Division. Please donate if we make you happy. https://give.umn.edu/gardener Replied August 18, 2026, 8:48 PM EDT

Black mold on some leaves of magnolia bush #942706

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