Native Plants

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Friday - November 21, 2008

From: Caledonia, MI
Region: Midwest
Topic: Pests, Trees
Title: Black coloration on Star Magnolia is probably sooty mold.
Answered by: Jimmy MIlls

QUESTION:

I have a star magnolia where 90% of the bark has turned black. It almost looks burned. The tree has decent buds set for next spring. What is causing the bark to turn black?

ANSWER:

The black coloration on your Star Magnolia is most likely due to sooty mold. Sooty mold is a fungus that grows on a sweet substance called honey dew. Honey dew is secreted by scale insects and aphids that feed on trees. If your Magnolia hasn't lost all of its leaves yet, you can probably find the sooty mold on the foliage as well. You should also look for scale insects clinging to the twigs of your tree. The sooty mold fungus is non-parasitic and probably will not damage the plant, but it is unsightly. The scale insects, on the other hand, are a problem that needs some attention.

I'm including links to four web sites that will make you more knowledgeable about Magnolia scale as well as sooty mold.

Magnolia Scale: Penn State University College of Agricultural Science and the Univeresity of Wisconsin Extension Service.

Sooty mold: University of Vermont Extension Service, and the University of Hawaii Extension Service

Another source of information closer to home would be to contact your County Extension Agent