In your situation, I first recommend getting a positive I.D. of the pest, because that's the only way to choose a truly effective solution. The possible culprits are aphids, which are tiny, soft-bodied pests that tend to congregate in masses on buds and new growth. First spray them off with a strong blast from your garden hose. Aphids can be controlled with insecticidal soap or neem spray as directed on the product label, both of which are friendlier to the environment than chemical options. Test any product on a few leaves before treating and entire plant to make sure the product isn't harmful to your plant.
I hope this information is helpful for the future. Good luck!
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When singular and plural spellings differ, as in peony and peonies, try both.