Preventative fungicide sprays applied early in the season help to suppress a recurrence of Brown Rot, and it's critical to also remove any fallen (or still attached to twigs) old, mummified fruit from last year, which harbors infectious spores. You can learn more in the pages linked below, which includes a preventative spray guide produced by Virginia Tech:

• Growing Stone Fruits in a Home Garden - Cherries, Peaches, Plums
• Brown Rot on Tree Fruit in the Home Orchard (PDF) -- Purdue
• Home Fruit Disease and Insects (PDF) -- Virginia Tech (you can keyword search this long document for Cherry and/or Brown Rot to find that specific information)

When to start applications -- and how often to re-apply a spray -- will depend on the particular fungicide used, so you can check the label information of any product under consideration in addition to the VA Tech guide above. In years with sufficient rain, the fungus that causes Brown Rot begins to be active when the flower buds are in the "pink stage," or showing some color as they get ready to open. Before buds begin to swell is the time to begin sprays, which given the current weather is probably going to be in the first half of this month, as edible (and flowering) cherries tend to bloom around early April in a typical year.

Miri