Dorene, here's the response to your question:

Thank you for writing.  That appears to be a purple lichen, brought out by the rain.  It should disappear when things dry out.  Lichens rarely damage a plant.
You could try using a macro lens to an extreme closeup.  Or you could send a sample to the University of MN Plant Disease clinic.
https://pdc.umn.edu/

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Steve Miles  Master Gardener, Hennepin County MN (Not an AI Bot)

I am always happy to receive follow-up questions if I do not fully address your question.
Sterilizing pruning tools prevents disease. https://extension.umn.edu/planting-and-growing-guides/clean-and-disinfect-gardening-tools

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