What are those black spots on my hydrangea (hosta/lilac/crape myrtle) leaves?

It is probably cercospora leaf spot, a common disease on many ornamental plants. Recommendations are to practice good clean-up and sanitation, use a soaker hose instead of overhead watering, apply fungicide appropriate for cercospora leaf spot in early spring — it’s not effective to cure already affected parts of the plant. Treat every 10-14 days while new growth is emerging. This disease is usually cosmetic and rarely kills the plant. In the future, you may want to select varieties that are resistant.

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