Why Are My Cherries Going Brown and Rotting on the Tree?

Cherries that turn brown and begin rotting while still attached to the tree — particularly in the weeks before and during harvest — are almost certainly affected by brown rot, a fungal disease that is one of the most widespread problems in cherry orchards worldwide. Brown rot can destroy a large proportion of the crop very rapidly, especially in warm, humid conditions, and the speed at which it spreads from fruit to fruit makes prompt action essential.

Identifying brown rot

Brown rot (Monilinia laxa and M. fructicola) begins as a small brown spot on the fruit surface, typically spreading from a wound, crack, insect entry point or damaged area. The brown discolouration spreads rapidly through the flesh, and within a day or two small white or cream-grey pustules of fungal spores appear in concentric rings on the surface. The fruit softens completely, shrivels and may either drop or remain mummified on the tree through winter, where it acts as a reservoir for the following season's infection.

Conditions that promote brown rot

Warm, humid weather in the weeks leading up to harvest creates ideal conditions for brown rot. Cracked fruit — from rain following a dry period — provides entry points for the fungus and dramatically accelerates infection. Trees with dense, overcrowded canopies where air circulation is poor and drying after rain is slow are consistently more affected than well-pruned, open-canopied trees. Birds and insects feeding on fruit also create entry wounds that allow the fungus to enter.

Removing infected material

Remove every affected fruit you can find as soon as you see it. This means fruit on the tree, fallen fruit on the ground, and any mummified fruit left from previous seasons. The spore clusters on brown rot-affected fruit are a direct source of ongoing infection — each one releases millions of spores in humid air. Do not compost infected fruit — bag and bin it. Clear fallen leaves from under the tree in autumn, as spores also overwinter there.

Improving air circulation

Open, well-thinned canopies dry faster after rain and are consistently less affected by brown rot than congested ones. Prune crossing and inward-growing branches during summer pruning to create a good open structure. Avoid encouraging lush, dense growth with excess nitrogen feeding.

Fungicide as a last resort

Where brown rot is a persistent annual problem, a copper fungicide spray before flowering and again after petal fall reduces spore load. In commercial orchards specialist fungicides are used, but in home gardens good hygiene and canopy management are usually sufficient.