Answer: Without seeing the plant, it's difficult to diagnose the problem. Mock Orange is susceptible to bacterial blight, which can show up as rusty colored areas on the leaves. I'd prune away the affected leaves and avoid overhead watering. If the spots show up again, you can use a fixed copper spray to help control the disease. Lilacs are also susceptible to bacterial blight so if your mock orange is planted near an infected lilac, they can reinfect one another. Best wishes with your garden!
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