Answer: There are no pests specific to petunia petals so only two possibilities come to mind: cutter bees, which leave little half-moon shaped notches in leaves and sometimes flower petals, or slugs. Snails or slugs feed at night so it isn't likely you'll see them during the day. You might venture out after dark with a flashlight to see if you can find the culprits. If so, handpick them, or set traps by inverting a clay pot in your garden and propping it up with a few stones. Slugs will hide in the pot and in the morning you can dispose of them. Good luck with your petunias!
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