The Q&A Archives: Black Excrement On Monarda And Dahlia Leaves

Question: I see tiny black (well-formed) spots on my monarda and dahlia flowers and leaves. These look like excrement left behind by something that is also eating the leaves. Do you know what the pest could be and how I can treat the same?

The black spots are on the leaves and don't look like they are part of the leaf. This is why I don't think it's any kind of fungus rot.

Answer: That does sound like a sign of some insect, but it's difficult to say what it might be. I suggest you continue monitoring the leaves--look carefully underneath and on stems in the area where the black spots are and you should be able to find the culprit. You might want to try using a magnifying glass and check at night for nighttime eaters. When you find the insect, send another question to the Q&A site (not my email address) with its description, as well as a description of the damage to the leaves. Then we can suggest an appropriate control. Good luck!

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