|For the last 3 years, my crepe myrtles have developed some sort of disease or pest infestation that turns the leaves and branches black and prevents the tree from blooming. We have used dishwashing liquid to clean them as well as other chemical treatments but it continues to come back. We have had to cut the trees back to the ground each year hoping to get rid of it but it keeps coming back.
|Answer from NGA
June 30, 2010
|The black is called sooty mold and it is the result of insects feeding on the leaves - in this case, probably aphids. When aphids feed they excrete a sticky substance called honeydew. When the honeydew ages it turns black. You'll need to stop the aphid feeding in order to get rid of the honeydew. It's difficult to get coverage on a tree but you can try spraying with insecticidal soap to take care of the aphids or you can use a systemic (Bayer Advanced systemic) to help protect your tree. Hope this helps and you see a big improvement next spring.
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