While cherry trees can certainly be beautiful while in full bloom, the homeowner stuck with cleaning up the fallen blooms and later, dealing with the flies that are drawn to the ripening fruit, may not be as enamored with the beauty of the blooming trees as are others. The only way to stop your tree from blooming and drawing flies, is to remove the buds before they have a chance to bloom out.
Monitor your tree for flowering bud formation. This should occur in early to mid spring for most cherry varieties, depending on your local weather conditions.
Prune all new growth with flowering buds before the buds have a chance to open completely. Use a ladder to reach buds in the higher branches. Pick up the cut branches with their buds and discard.
Watch for buds that you missed with your pruning. Use a garden hose with a high pressure nozzle to knock down any blooms that open. No blooms--no fruit. No fruit--no flies that are attracted to the fruit.