Prevention and control Bitter pit can usually be prevented with careful management. The aim should be to maintain conditions that allow steady, uniform growth throughout the season as this will avoid rapid fluctuations of calcium in the trees. Keep the tree mulched, applying the mulch early in the season when soil moisture levels are still high. In very dry seasons, irrigate to stop the soil drying out. These include Bramley's Seedling, Edward VII, Newton Wonder and Merton Morcester.
Commercial growers provide extra calcium to the fruit by using a foliar spray or post-harvest dip.
This is not a very practical method for the domestic gardener as the spraying, with calcium chloride, needs to be very thorough and carried out every 10 days from June onwards to be effective. There is evidence that summer pruning can be beneficial as it reduces competition for calcium between fruit and shoots. It should be done in August when extension growth has slowed down and terminal bud formation is visible. When late summer pruning is practised only minimal winter pruning is required. Cut out all vertical one year old shoots, i.e. any upward or downward pointing shoots.