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Navel Orange Internal Black Rot: Alternaria Fruit Rot

Identifying Black Cavity in Navel Orange

A perfect-looking navel orange with a 1-inch black area inside near the rind has Alternaria fruit rot (black rot)—a fungal disease affecting the fruit interior.

Alternaria Fruit Rot Facts

Primarily attacks lemons and navel oranges.
Fungus (Alternaria alternata) enters at stylar end (navel) or through micro-cracks.
Develops internally—exterior looks perfect.
Makes affected portion inedible (toxic metabolites possible).

Prevention in the Grove/Garden

Consistent irrigation: Drought stress predisposes fruit. Never let trees dry out.
Balanced nutrition: Adequate Ca, B, K strengthen rind integrity.
Sanitation: Remove all dropped/mummified fruit. Prune for air flow.
Post-harvest handling: Avoid bruising. Cool promptly.

About "Atomic Grow" Claims

Products claiming to "raise brix to prevent fungal rot" lack scientific validation for Alternaria control. Proven cultural practices above are the standard.

One affected fruit ≠ tree problem. But if recurring, review irrigation and nutrition.

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