Brown buds that fail to open on peonies and some roses, especially the white and pink flowered varieties are likely the result of Botrytis Blight also known as Gray Mold.
This fungal disease is most common in cool rainy as well as humid weather. The disease attacks a variety of ornamental and edible plants and often is specific to the plant part infected.
The bud blast and flower blights we see here may also occur on mums, dahlias, dogwood, geraniums, hydrangea, marigolds, and sunflowers.
Look for the fuzzy gray growth and small black specs on the dead tissue.
Remove infected parts and place in a paper bag for disposal. And don’t compost. Only clean up during dry weather as moisture helps spread the blight.
Ongoing sanitation, fall clean up and better weather is usually enough to keep this disease under control.