Q I’ve been told that my apples have bitter pit. What is this?
A Bitter pit is a physiological disorder that only affects apples. It causes small, dark, slightly sunken patches on the skin and brown specks in the fruit.
Caption: Bitter pit causes marks on the skin and flesh
Q What causes this problem?
A A lack of calcium, perhaps because there’s not enough calcium in the soil, but, more often, it's linked to lack of water or a very heavy fruit crop. These two factors can mean that not enough calcium is carried to the fruit, so it doesn’t develop properly.
Q Can I still eat the apples?
A Yes, although if the bitter pit is extensive the fruit may be unpalatable. Fruit with bitter pit does not store well, as the damaged areas tend to rot.
Q Can it be cured?
A You can’t cure it once the apples are damaged, but you can help to prevent it in future seasons. First, try improving the tree’s water supply. Mulch in spring, when the soil is moist but not saturated. Our tests show that black polythene or grass clippings are very effective. If you dislike their appearance, cover with chipped bark.
In very dry spells, when soil is still dry 30cm down, water at the rate of 20-50 litres weekly per tree, depending on the size of the tree. Repeat this until there is a good downpour. Combine this with summer pruning and fruit thinning to reduce the size of the crop.
If your soil is acid, add enough lime to raise the pH to about 6.5. If this doesn’t do the trick, spray the tree with calcium nitrate solution (50g per 5 litres) every three weeks from late July to late October.
Q Does this happen to all apples trees every year?
A Bitter pit doesn’t usually occur every year, but some varieties are more susceptible than others. Young vigorous trees are often worst affected. Avoid the most susceptible varieties such as 'Bramley's Seedling', 'Cox's Orange Pippin', 'Crispin' ('Mutsu'), 'Egremont Russet', 'Gala', 'Golden Delicious', 'Jonagold', 'Jupiter', 'Merton Worcester' and 'Newton Wonder'.