Answer: Ants don't cause any harm to the buds -- they are simply drawn to the sweet droplets of moisture exuded by the buds. Your peonies may have a fungal disease, but my guess is that they are infested with thrips -- tiny insects that burrow into buds and drink their juices. Thrips are especially a problem on light-colored blooms, and not just peonies. They also damage roses, hollyhocks, and gladiolas, among others.
If you have any of the fallen buds, take a closer look to see if you can identify the symptoms of thrips -- pale, desiccated tissue and dark fecal matter. The bugs themselves are hard to see because they're tiny, and the adults flit away as you approach. You can control thrips by applying insecticidal soap sprays frequently to the unopened buds. A neem-based repellent may also work to keep the thrips at bay. Thrips usually attack plants that are drought-stressed. If your peonies are growing in a well-drained, sandy soil, add some compost to the area, keep them mulched and well watered. Add a fresh layer of compost every spring. During the summer, spritz them monthly with a seaweed fertilizer solution to keep them growing vigorously.
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