Black soot on my citrus trees - Knowledgebase Question

Jacksonville, Fl
Question by lawpatricia
November 23, 2009
I have some kind of black soot covering the leaves of my citrus trees.Part of it will wash off with a high powered nozzle but some of it remains and the rest kust comes back.Is it some kind of mildew and how do I get rid of it?

Answer from NGA
November 23, 2009


If the black substance is shiny and can be scraped off with a fingernail, or washed off with water, it is sooty mold. This substance is the result of insect feeding higher up in the plant. As insects such as aphids feed, they exude a sticky substance called honeydew. There is just enough sugar content in the excretion to grow mold and the substance is then called sooty mold. Insecticidal soap is effective against aphids so once you get the aphid population under control you shouldn't have any more problems with sooty mold. Other insects can feed on citrus leaves so carefully check the undersides of the leaves and the petioles where the leaves meet the stems. Scale or mealybugs might be present. Best wishes with your tree.

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