The Physiological Disorders section of the card set includes most the common disorders of physiological origins found during the sorting and packing of Washington apples. Bitter pit, scalds and lenticel conditions are just a few of the items presented in this section. The upcoming revision of the Defects & Disorders Guide may include additional forms of physiological disorders such as emerging conditions or reclassified disorders. To navigate directly to the pest damage of interest use the links below this text block. The card images shown on this site are slightly modified from their original form to accommodate web formatting. Any reproduction of the card images or content without permission is in violation of WSU Copyright policies.
Bitter pit Superficial scald Senescent scald Core flush Internal breakdown Braeburn browning Watercore Lenticel breakdown Lenticel blotch pit CO2 injury Chlorine burn Chilling injury Humidity disorders
Bitter Pit (BP) is a disorder that begins in the orchard and is related to low calcium. Effected cells gradually die, but fruit may show no sign externally at harvest. Early external symptoms begin as slightly water soaked spots or patches, later developing into darker, sunken spots as the tissue below dies and begins to desiccate. Below the skin, the affected flesh is brown and corky, which distinguishes BP from other disorders. This disorder is easily confused with stinkbug damage or lenticel blotch pit. The symptoms are usually on the lower half of the fruit, unlike stinkbug damage. However, in severe cases the spotting may extend to the upper half as well.
Superficial scald is a very common post-harvest disorder. The appearance and severity depend on the susceptibility of the variety with Granny Smith and Red Delicious being among the worst affected. The skin of the affected fruit turns brown in patches, especially on the shaded side and may become rough. Only the surface of the fruit is effected with the flesh remaining firm and of eating quality. The margins between normal and affected skin are diffuse. Browning develops rapidly once the fruit is moved from cold storage to room temperature.
Senescent scald appears as brown patches on the skin that may become sunken and rough with distinct margins, often ribbon like. Unlike superficial scald, senescent scald usually appears on the sun exposed side of the fruit and on late harvested fruit. Golden Delicious and late harvested or over-stored fruit may be susceptible to senescent scald. Unlike superficial scald, the interior of the fruit may have brown flesh and have internal breakdown.
Core flush, a form of senescent breakdown is common in Granny Smith, Braeburn and other apple varieties. The core area turns pink then brown. The discoloration starts near the core and extends with wedges of brownish tissue outward. The discoloration may circle the core partly or completely. The affected tissue is moist and softer than unaffected tissue. In severe cases it may extend just below the skin. There is no exterior symptom.
Over-mature and large fruit are highly susceptible to internal breakdown. Internal breakdown is characterized by flesh browning and breakdown. Internal symptoms may be restricted to one side of the fruit, or involve the entire fruit. Often there is a 1/4 inch ring of healthy flesh surrounding the affected tissue. The sun exposed side or the calyx end is more often affected with the rest of the fruit normal. The skin of affected fruits may be normal, or dull and dark, and in later stages of the disorder it sometimes becomes cracked.
The apple variety Braeburn is susceptible to an internal disorder called Braeburn browning disorder (BBD). At harvest, this disorder has the appearance of light to dark brown areas similar in nature to watercore, but occurring without pattern anywhere in the flesh. Symptoms of BBD developing in storage include tissue browning resembling the internal cavities caused by CO2 injury. However, BBD is thought to be related to late harvest.
Water core appears as water soaked areas of the flesh first associated with vascular bundles. In severe cases, the effected tissue may spread covering large areas of the flesh. In these instances, watercore is externally visible by the appearance of translucent skin blotches on lighter pigmented apples, or as very dark patches on darker fruit. In mild cases, watercore will disappear (sugar re-absorbed) early on during cold storage. However if severe enough, watercore may develop into internal breakdown (watercore breakdown).
Lenticel breakdown is a physiological disorder effecting the surface of apples. Before the packing, there is little evidence of a problem; however, within a few days of packing, symptoms appear as dark brown pits in the fruit skin around the lenticels reducing marketable yield. It usually occurs on the less sun exposed side and along color margins. Early symptoms appear as small dimples. As firmness decreases, pits grow in size and depth. The flesh is not deeply effected except for a possible cavity directly under the pits. Lenticel breakdown is easily confused with lenticel blotch pit. A dye test has been developed to help determine fruit susceptibility to this disorder at harvest.
Lenticel Blotch Pit
Lenticel blotch pit is similar in appearance to both lenticel breakdown and bitter pit. Lenticel blotch pit has irregular patches around the lenticels, unlike the more defined circles found in lenticel breakdown; and are usually near the calyx end as in bitter pit, or on the more sun exposed side of the fruit. Unlike lenticel breakdown, the flesh browning may extend deeper, as with bitter pit, and will likely increase and deepen after harvest. Hastening ripening will increase symptoms.
Carbon Dioxide (CO2) Injury
If the carbon dioxide (CO2) level is too high during controlled atmosphere (CA) storage both external and internal injury symptoms may occur. External injury resembles snowflake-like patches which may join to form one very large patch. Internal symptoms appear as discolored areas within the vascular bundles. The tissue may be brown and develop pockets. A noticeable aroma of fermentation may be present when CA storage is opened, or the fruit is cut.
Sodium hypochlorite (chlorine bleach) is commonly used in dump tanks as a disinfectant. It is important that the chlorine concentration be monitored. If the concentration is too low the tank water no longer works to disinfect. However, if the concentration is too high the fruit can be burned.
Fruit stored below their tolerance point may show a variety of symptoms depending on the cultivar, temperature and duration of storage at the adverse temperature. Symptoms may vary from browning of the skin to deep flesh browning and translucency. Dry internal cavities and flesh browning may also develop. Fruit also may have a bitter taste and smell of fermentation upon cutting.
Excess or too low humidity can have a detrimental effect on fruit during storage. If the humidity is too high the cells swell and expand to the point where the tissue cracks. Too low humidity causes dehydration of the tissues leading to shriveling.