It is also likely, however, that irreversible damage to organelles and membranes may occur due to excessive thermal injury before these visible symptoms. In some years, it appears the fruit is conditioned by gradual climatological change to tolerate the imposed heat stress, whereas in other years a sudden change in weather may bring about the injury quite suddenly. Bitter pit of 'Fuji' apple. Areas of brown, dry tissue developing initially in the flesh are characteristic of bitter pit. Affected areas are usually most numerous towards the calyx end of the fruit.
Symptoms can appear prior to and following harvest.
The disorder results from low fruit calcium content relative to potassium and magnesium concentrations. Fuji' is most prone to development of this disorder when light crops of large fruit are produced on young trees. Bitter pit incidence can be reduced by management practices that result in regular annual cropping, vigor control and harvest at proper maturity. Postharvest calcium treatments can also minimize the disorder, but water sanitation is critical to avoid fruit inoculation with disease organisms. Controlled atmosphere storage can also reduce bitter pit incidence.