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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Thursday - September 23, 2010

From: San Marcos, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Sooty mold on Sophora secundiflora in San Marcos, TX.
Answered by: Jimmy Mills

QUESTION:

Dear Mr. SP, We have a Sophora secundiflora that is suffering with very black mold or fungus on most of its leaves. Last year, I washed it leaf-by-leaf with soapy water but it's getting too big to continue that. The tree right next to it shows no sign of the problem. The cover is so thick that the tree, except for new growth, looks black. Any suggestions?

ANSWER:

What you are experiencing is an attack of sooty mold on your your Mountain Laurel. The sooty mold is a fungus, and while it  isn't particularly harmful to your plant, it is unsightly. The fungus is growing on honey dew which is a sticky substance that is being excreted by aphids or other scale insects as they feed on your plants. Since the aphids are so small, they are often not noticed until the sooty molds tips you off to their presence. If the sooty mold becomes thick enough, it can prevent leaves from receiving adequate sunlight.

Here are three sources of information about this problem. The University of California at Davis Integrated Pest Management Program has two good articles; one on sooty mold, and one on aphids. This article from the USDA tells how to recognize and control sooty mold.

 

 

 

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