Bitter pit: how to recognise and treat it

Deficiency

Bitter pit — Photo: Rasbak, CC BY-SA 3.0, Wikimedia Commons

Symptoms

Small sunken spots on the apple skin, mostly towards the blossom end, that darken to brown.
The flesh under the spots turns brown, dry and spongy.
Spots may show just before harvest but often appear only after storage.

Organic treatment

Keep soil moisture steady by watering during dry spells.
Cut back on nitrogen feeding and heavy pruning, which push leafy growth that takes calcium from the fruit.
Pick at proper maturity, not too early, and cool the fruit promptly after harvest.

Chemical treatment

Foliar sprays of calcium chloride or calcium nitrate about once a month through summer; follow the label dose.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Expect more bitter pit on susceptible cultivars such as 'Granny Smith', 'Honeycrisp', 'Jonathan' and 'Golden Delicious'.
Thin fruit moderately; overthinning leaves fewer, larger apples that pit more.
Avoid a light crop on a vigorous tree, as young and heavily pruned trees are most affected.

Plants it affects

Apple

Sources

Figures checked against these sources.