Prune and fertilize peach trees in spring. Inspect your peach trees for brown, blighted or infected blossoms or shoots with brown, gummy cankers. Prune branches to remove any blossoms or cankers that may spread brown rot. Prune healthy branches to increase air circulation and light, both of which can help prevent brown rot. Fertilize around the tree with 12-12-12 fertilizer in early spring to keep trees well nourished and capable of fighting brown rot.
Spray peach trees with fungicide in spring just after the buds begin to turn pink. Apply immunox according to the label's directions. Adjust the application amount depending on the size of your orchard. Remember that fungicides must be applied prior to the appearance of brown rot to be effective.
Apply fungicides to the peach tree throughout the season before harvest. Alternate or mix immunox with captan or sulfur according to the product's directions to prevent trees from developing resistance to immunox. Continue to apply fungicides as directed until one week prior to harvest.
Thin mature peaches so that they do not touch each other. Remove any exceptionally small fruit. Pick up and dispose of any unused peaches if they are thinned after the pit has hardened. If the pit has not yet hardened, fruit can be left on the ground and will decompose quickly without exacerbating brown rot fungus.
Remove all fruit from the tree after the final harvest. This can prevent twigs from becoming infected with brown rot during dormancy.