Bitter Pit

Abstract

Bitter pit is evident on affected fruit, particularly apples, as small sunken pits in the skin under which the flesh is dead, brown and bitter (Figs. 7.1 and 7.2). These are most commonly noticed first at the calyx (flower) end of the fruit and progress toward the peduncle (stalk). As more cells die the flesh of affected fruit gradually turns brown, progressing from beneath the skin towards the core. Sometimes fruit becomes irregular as the disease distorts it. Cobb (1903) referred to this as ‘stigmonosis’, a term later also used by McAlpine (Fig. 7.3). As the extent of dead cells increases the fruit becomes inedible and of no use in any other way. For reasons still not fully understood, the incidence of the disorder increased dramatically over the last decades of the nineteenth century. In part this may have been due to the gradual depletion of certain soil minerals and increases in soil acidity. The condition often severely limited the commercial yield of trees of susceptible cultivars, especially if lightly laden with oversized fruit. The incidence of bitter pit was increased by picking fruit before it was fully mature, and by not storing it under cool conditions. When apparently sound fruit was picked and sent to market, there was still little guarantee that it would be edible after a month in local storage or shipment to Europe. Fruit with bitter pit was unsaleable. In 1910, McAlpine (1910a) reported a trial at Burnley in which, at harvest, 67.5 % of fruit was pitted and after a further 26 days in storage, 90.7 % was pitted and unsaleable. This was not uncommon in localities where the incidence of bitter pit was high and the most susceptible varieties were grown. It was disastrous for orchard businesses reliant on varieties such as Cleopatra or Annie Elizabeth in localities conducive to bitter pit.