Tree Fruit Research & Extension Center

Cullage Assessment & Education

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Quick Identification Guide to Apple Postharvest Defects & Disorders Cards

Physiological Disorders

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. At a later date more cards may be developed for this section which would include any emerging or reclassified disorders. For ordering information vist the Additional Information section of the Introduction. The cards shown below are slightly modified to accomodate web formatting. Figures may appear fragmented in some browsers. Please report viewing problems here. Any reproduction of the card images or content without permission is in violation of WSU Copyright policies.


PHYSIOLOGICAL: Bitter Pit  

Bitter Pit (BP) is a disorder that begins in the orchard and is related to low calcium. Affected 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 stink bug damage or lenticel blotch pit. The symptoms are

usually on the lower half of the fruit, unlike stink bug damage. However, in severe cases, the spotting may extend to the upper half as well.

Figure 1: A Granny Smith showing spots which are larger and more diffuse with irregular edges.

Figure 2: A Golden Delicious with the more common pinpoint-type spots.


PHYSIOLOGICAL: Superficial Scald  

Superficial scald is a very common postharvest disorder. The appearance and severity depends 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 affected, 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.

Figure 1: Superficial scald appears as brown rough patches on this Granny Smith apple.


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PHYSIOLOGICAL: Senescent Scald  

Senescent scald appears as brown patches on the skin that may become sunken and rough with distinct margins, often ribbonlike. 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.

Figure 1: Golden Delicious fruit showing senescent scald after cold storage.


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PHYSIOLOGICAL: Core Fush  

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 partially 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.

 

Figure 1: Core flesh starts to turn pink.

Figure 2: The pink gradually turns brown.


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PHYSIOLOGICAL: Internal Breakdown   

Overmature 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 1/4th 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.

Figure 1: Overmature Granny Smith apple with extensive internal breakdown with only slight bruiselike discoloration on one side of the outer skin (right side).


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PHYSIOLOGICAL: Braeburn Browning   

 

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.

Figure 1: Sliced Braeburn apples show the progression of severity of BBD.


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PHYSIOLOGICAL: Watercore   

Watercore appears as water-soaked areas of the flesh first associated with vascular bundles. In severe cases, the affected 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 reabsorbed) early on during cold storage. However, if severe enough, watercore may develop into internal breakdown (watercore breakdown).

Figure 1: A Granny Smith apple showing the clear skin blotches on the slice, exposing the water-soaked flesh beneath.

Figure 2: When the fruit is cut crosswise, a pinwheel pattern of water-soaked flesh is exposed. In severe cases, the tissue will turn brown as it breaks down and decays.


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PHYSIOLOGICAL: Lenticel Breakdown   

Lenticel breakdown is a physiological disorder affecting 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 affected 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.

Figure 1: Gala apple showing moderate lenticel breakdown symptoms.


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PHYSIOLOGICAL: 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.

Figure 1: Fuji apple showing lenticel blotch pit on the lower half of the fruit.

Figure 2: Cutting through a blotch exposes corky tissue browning similar to bitter pit.


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PHYSIOLOGICAL: Carbon Dioxide 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 snowflakelike 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.

Figure 1: A Golden Delicious apple with external CO2 injury showing irregular (snowflakelike) margins.

Figure 2: Internal CO2 damage with brown flesh and pockets.


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PHYSIOLOGICAL: Chlorine Burn   

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.

Figure 1: The stem bowl and calyx are susceptible to burning because they fill with water, increasing the exposure time to the chlorine.

Figure 2: In cases of elevated chlorine concentration in the tank water, the entire fruit surface is vulnerable to chemical burning.


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PHYSIOLOGICAL: Chilling Injury   

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.

Figure 1: A Red Delicious apple showing external browning and skin translucency.


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PHYSIOLOGICAL: Humidity Disorders   

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.

Figure 1: A Golden Delicious apple showing cracking at the lenticels. If conditions are severe enough, the cracks will expand, resulting in large, deep, branching cracks extending across the fruit. Often the cracks will become infected, and the fruit will decay.

Figure 2: The Gala shown here was stored at too low relative humidity and became shriveled.


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