Crepe Myrtle Turning Black

Why are the stems and leaves on my Crepe Myrtles turning black?

Aphids and azalea barkscale feed on the sugars produced by Crepe Myrtles. The insects’ digestive systems do not process all of the material they eat. The undigested sugars pass through the insectsand are deposited on the leaf orstem where the insects are feeding. This excretion is called honeydew. Honeydew has a high sugar content and is sticky to the touch. Honeydew is a perfect medium for the growth of black sooty mold. This black mold is what you are seeing on the twigs and limbs of Crepe Myrtles. To eliminate the black sooty mold, it is necessary to stop the production of honey-dew. To eliminate the honey-dew it is necessary to managethe insects producing it. Azalea bark scale can be managed with appropriately timed applications of horti-cultural oi l . We are alsoexperiencing great resultsmanaging aphids, azalea barkscale, and thus sooty mold,with the systemic insecticide,Merit®. A single soil injectionapplication between late winterand early spring provides ayear’s management. The Crepe Myrtles also benefit from the soil injection process, which includes fertilization and soilaerification. Your arborist candesign a management programthat best meets your needs.

by Chris Brewer – I.S.A. Certified Arborist

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