Bitter pit

What you see

Small sunken dark pits in the apple skin, with corky brown dry spots in the flesh beneath, usually worst at the calyx end. Often appears only after several weeks in store on fruit that looked perfect at picking.

Conditions

Big fruit on a young, vigorous, heavily pruned tree in a dry season. Calcium moves only in the transpiration stream and fruit transpires poorly, so it is a distribution failure, not a shortage in the soil.

Treatment

Nothing can be done to affected fruit - it is safe to eat, just cut out the pits. Foliar calcium sprays through summer help the following crop.

Prevention

Water evenly through summer and mulch. Avoid heavy winter pruning and heavy nitrogen, both of which push vigorous growth that competes with fruit for calcium. Thin the crop so fruit does not grow oversized.

Months: July, August, September, October, November

Plants

Apple, Pear

Remedies

Mulch, Seaweed extract

The thing people get wrong

Adding lime to the soil is the standard response and it almost never helps, because the soil usually has plenty of calcium - the problem is getting it into the fruit. The counter-intuitive fix is to make the tree less vigorous: less nitrogen, lighter pruning, steady water. A hard-pruned, well-fed young tree carrying a few enormous apples is the perfect recipe for it.