Why Do My Apples Have Bitter Pit Brown Spots Inside?

Small, brown, slightly sunken pits in the flesh of apples — concentrated just below the skin, particularly toward the calyx (flower) end of the fruit — with a noticeably bitter or off taste at the affected spots, are the defining symptoms of bitter pit. Bitter pit is not caused by a pest or pathogen but by a physiological disorder: a localised calcium deficiency in the developing fruit flesh that causes cells to die and form the characteristic cavities. The disorder develops in the fruit during the growing season but symptoms may not be fully visible until storage.

Why calcium deficiency occurs in the fruit

The soil may not be low in calcium — bitter pit frequently occurs in soil with perfectly adequate calcium levels. The problem is calcium transport within the tree. Calcium moves through the tree primarily in the water stream (xylem flow), and developing fruit has very low transpiration — it draws relatively little water compared to leaves. During periods of drought stress, uneven watering, or when the crop is very large, the competition between fruit and leaves for the available calcium supply is won by the leaves (which transpire actively and draw calcium constantly). The fruit receives insufficient calcium to maintain normal cell function in its outer layers.

Foliar calcium sprays — the primary prevention

Apply calcium nitrate or calcium chloride solution (0.4–0.6% concentration) as a foliar spray directly onto the developing fruit, starting three to four weeks after petal fall and repeating every two to three weeks through fruit development — typically four to six applications through the season. This delivers calcium directly to the fruit surface and bypasses the soil-to-root-to-fruit transport pathway entirely. This is the most reliable prevention available. Calcium chloride is slightly more effective at reaching the fruit but may cause skin russeting on some varieties — test on a small area first.

Watering and irrigation consistency

Consistent soil moisture prevents the drought stress that disrupts calcium transport. Mulch deeply and water regularly during dry periods from fruitlet set through to harvest. Irregular wet-dry cycles are the most common management factor that exacerbates bitter pit.

Susceptible varieties

Cox, Bramley, Jonagold and Egremont Russet are among the most bitter-pit susceptible varieties. Varieties with large fruit are more susceptible than small-fruited types — larger cells are more calcium-hungry.