Why Does My Apple Have Brown Patches Inside the Fruit?

Cutting open a perfectly good-looking apple to find brown, discoloured or soft patches inside — when the exterior appeared completely normal — is a common and confusing problem. The internal browning is invisible until the fruit is cut, making it difficult to detect during harvest or inspection. Several different conditions cause internal apple browning, and identifying which one is responsible determines the right response and tells you whether the fruit is still usable.

Bitter pit — calcium deficiency disorder

Bitter pit produces small, brown, slightly sunken cavities in the flesh, concentrated just below the skin surface on the shoulder end of the fruit. Affected flesh tastes bitter. It is caused by insufficient calcium reaching the developing fruit — not necessarily low soil calcium, but disrupted calcium transport caused by uneven watering, excessive nitrogen or potassium fertiliser, or irregular fruit development. Foliar calcium sprays (calcium nitrate or calcium chloride) applied at fruitlet stage and repeated several times through fruit development significantly reduce bitter pit incidence.

Core rot (mouldy core)

Core rot is caused by fungi entering the fruit through the open calyx end (the remnant of the flower at the base of the fruit) and growing inward toward the core. The flesh around the core develops brown, often mouldy areas while the rest of the fruit looks and feels normal. The calyx end is the entry point — varieties with an open calyx tube are most susceptible. Affected fruit is safe to eat if the brown area is removed, but core rot spreads in storage, so use affected fruit promptly.

Storage breakdown (internal browning)

Apples stored in conditions that are too cold (below 2°C for many varieties), too warm, or with incorrect atmospheric composition can develop internal browning — a physiological condition where the fruit's cells die and turn brown while the skin remains intact. This is a storage disorder rather than a disease. Store apples at 3–4°C (never frozen), in a cool but not freezing environment, and check regularly.

Codling moth damage

Codling moth larvae create a tunnel leading from the skin surface to the core. The tunnel and surrounding flesh show brown discolouration. Unlike bitter pit or core rot, codling moth damage is a clearly defined tunnel, often with frass, leading directly to the seed cavity.