Aphids!. The ants are atttracted to the aphids which they 'milk' for the honeydew which the aphids secrete. The ants will even move aphids from plant to plant to keep the supply going. Kill the ahids and find the ants nest and get rid of it. The damage to the Paeony is by the aphids.

I've had this problem too and no sign of aphids. The buds are still tight so I sprinkle them with ant powder. I did this last year too and the flowers came out fine, it doesn't seem to affect the plant.

Ants also remove the resin from Paeony buds and this helps the buds open.

thanks for the suggestions.there are no aphids on the peonies so i will try the ant powder on the buds and see what happens

Oh, maybe the ants are useful after all. I always think bad of them when I see them, I need to think more!!