More information on the fungal disease that causes brown rot can be found at the Online Guide to Plant Disease.
On callery type pears, flowers are not infected as frequently as the leaves. In Prunus, infected flower parts turn light brown and may develop areas of buff-colored (M. fructicola) or gray (M. laxa) spores. Infected petals may look water soaked, which can be mistaken for frost injury. Flowers generally collapse as the fungus invades through the pedicel. Infected flowers often adhere to twigs and spurs through harvest or even winter.