Thank you for the image. It reveals that your cherries have a common disease, Brown Rot Blossom Blight and Fruit Rot. This year, the frequent light rains have been especially favorable for this disease among the various Prunus species.
Treatment has two required phases: 1.) Cultural and 2.) Chemical.
1.) Cultural management is the only helpful thing possible you can do this year.
a.) Collect all affected fruit, both on the tree and on the ground; discard in the trash.
b.) Some affected fruits (called mummies) will dry and cling to the tree through the winter. Remove, and discard, them when you see them because they are a major source of infection spores the following spring.
c.) Prune out dead twigs and branches during dry weather in the summer.
2.) Chemical treatment consists of an annual spray to minimize recurrence of the disease. Mark your calendar for bloom time next spring.
Four products are available to home gardeners. Choose from the following, then read and follow label directions to apply:
- Bonide Captan 50 WP
- Ortho MAX Garden Disease Control
- Infuse Systemic Disease Control
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens.
Apply fungicides during the bloom period at early popcorn (red bud, pink bud, or green tip), full bloom, and/or petal fall to control the blossom blight phase.
If the tree is too large for you to easily spray, consider hiring a pest control company as they will have the appropriate equipment.