Answer: If there is no damage on the leaves, watch the flowers as they unfold. It is possible that a bud worm is munching on the flower inside the bud and the damage is already there as the petals unfurl. If so, there may be no way to stop the damage other than closely inspecting the unopened buds and pinching off any that have a tiny worm hole in it. By picking and destroying these flower buds you'll kill the larva, preventing it from becoming an adult to lay eggs on your flower buds. The only other insect that might damage the flower petals are slugs. They aren't interested in the hairy leaves or stems but love the soft petals. You might try scattering some iron-based slug killer around the base of your plants.
Best wishes with your petunias!
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