Market Diseases of Apples, Pears, and Quinces: Internal Breakdown

Internal breakdown caused by old age

Internal breakdown hastened by water core

Senescent breakdown, Jonathan

Mealy breakdown, Tesaurus

Mealy breakdown, Gala

Mealy breakdown, Gloster

Mealy breakdown, Braeburn

Market Diseases of Apples, Pears, and Quinces
Internal Breakdown

Occurrence and importance
Internal breakdown occurs in apples grown in all of the fruit-growing sections of the United States. It has been observed most often in Jonathan, Northern Spy, Stayman, Rome Beauty, Wagener, and certain summer varieties that quickly become overripe; but Delicious, Yellow Newtown, Baldwin, and Rhode Island Greening are also frequently affected. The incidence of internal breakdown varies from year to year, apparently being affected by preharvest growing conditions. The disorder can cause heavy losses during the storage season, particularly in large and over-mature apples. Its appearance on the market is spotty. Since apples normally have to be cut to detect internal breakdown, the consumer doubtless sustains indeterminate losses each year.

Symptoms
The disease is characterized by breakdown and browning of the apple flesh (top photo). It may be restricted to one side or to tissues around a bruise but may also involve the entire fruit. Sometimes an outer shell of healthy flesh about 1/4 inch thick surrounds a brown zone that in cross section extends inward in roughly triangular patches as far as the vascular bundles or a little beyond, next to this is another zone of healthy flesh, and in the flesh at the core is a second area of brown. The condition just described is especially common in Jonathan and Delicious. The riper side of the apple is affected more often than the greener side and the calyx half more often than the stem half. The skin of affected fruits may be normal, or dull and dark, and in later stages of the disease it sometimes becomes cracked.

Internal breakdown is sometimes mistaken for freezing injury. The browning associated with freezing injury may occur anywhere in the apple and is independent of maturity. Bruises on frozen fruits extend radially into the deeper tissues. On the other hand, internal breakdown at a bruise rarely assumes a radial direction but includes more of the surrounding tissues and is mealier.

Causal factors
Internal breakdown occurs most often on large, over-mature apples. It is also favored by delays in harvest and in cooling and by storage at temperatures above those recommended for the variety.

Internal breakdown indicates the approaching end of the storage life of apples when they are not affected by fungus rots. It may, however, occur earlier than normal as a result of unfavorable growing conditions or certain handling or storage practices and may follow water core (second photo), freezing, or bad bruising.

Control measures
The little that can be done to control internal breakdown after picking is best done by placing fruits promptly in cold storage at 31° to 32 °F. Fruits with a decided tendency toward breakdown cannot be relied on for late keeping even in cold storage. Seriously water-cored fruits should be marketed as soon as possible.