Tree Fruit Research & Extension Center

Cullage Assessment & Education

Apple Postharvest Disorders

Introduction

Before fruit are packed for market they must undergo sorting for size, and other general quality factors, as well as for defects. The fruit removed during sorting are referred to as Culls. Although most of the fruit are usually culled for failing to meet grade standards (size or shape, color, sugar, firmness), many of the fruit have defects. The defects may be due to disease agents, physiological disorders, insect feeding, or mechanical injuries. Cull analysis is the process in which the cull fruit are scored for the defects they have. This can be a frustrating task because many of the defects can be difficult to identify. Some defects look different depending on the cultivar or severity of symptoms; some defects only appear on certain cultivars; some defects look very similar making it hard to differentiate; and sometimes there are more than one defect (more often than not) that may change or hide each other's appearance.

Unfortunately, there aren't many identification guides available in print or on the web to assist with visual identification. There are several references on the web that give excellent written descriptions of the defects along with possible causes, but no, or poor images. Web page is intended to be an image gallery to assist with a 'best guess' identification. I would suggest following up the identification with the written references for confirmation. Apple pathogens are not included here but I have a link to Dr. Xiao's pathology page in the left hand column. Also to the left is a link to Dr. Schaeder's Fruit Finish reference that covers sunburn and related disorder in much more detail. At the end of this page are references, both online links and written citations, to aide in disorder identification.

Nutritional Disorders - External

In general, Nutritional Disorders have a Pre-harvest origin and are mostly due to a mineral imbalance within the tree. This can be caused by improper fertilization, pruning practices, weather, irrigation, disease, or other stress inducing factors in the orchard. With so many factors, there is no easy fix. Diagnosing the fruit disorder is the first step in correcting orchard practices.

 

Bitter Pit

bitter pit GS

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bitter pit GS slice

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Symptoms:

The images above are two examples of how Bitter Pit (BP) may appear. Notice that in both cases the spots or blotches appear on the lower half of the fruit. However, in highly susceptible varieties, the symptoms may extend up to the fruit shoulders. In the first example, the spots are larger and more diffuse with irregular edges compared to the second example with more pin-point type spots. In both cases the spots are slightly sunken. Below the skin, the flesh is darkened and corky, which distinguishes BP from other disorders. This disorder is easily confused with stinkbug damage. See the link: Commonly Misidentified Disorders for a comparison of BP and Stinkbug damage. Bitter Pit actually develops pre-harvest effecting small areas of cortical tissues at the terminals of vascular bundles. The affected cells gradually die, but fruit may show no sign externally at harvest. Early external symptoms begin as slightly water soaked in appearance, later developing into darker, sunken spots as the tissue below dies and begins to desiccate.

Possible Confusion:

Stinkbug feeding; Drought Spot.

Susceptible Varieties:

Bitter Pit can affect all apple varieties.

Possible Causes:

Bitter Pit is associated with the following orchard conditions: unusually warm temperatures and periods of water stress while fruit matures; early (immature) picking; large fruit size because of low crop load; excess tree vigor; excessive thinning; high levels of Potassium and Magnesium relative to Calcium concentration within the fruit; delaying cooling after harvest; and high storage temperatures.

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Jonathan Spot

Jonathan Spot

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Symptoms:

Jonathan spot is usually associated with the lenticel. In the early stages, or on certain varieties, Jonathan spot appears as small brown or black spots about 1/8th of an inch around and including the lenticel. The spots may further enlarge with the affected skin turning very dark on red or blushed fruit, or yellow to light brown on yellow or green skinned fruit. As spots grow they may merge forming off-colored, irregularly shaped patches. The lenticel itself is darker than the surrounding area and sunken. The area around the lenticel may also be slightly sunken, but generally the discolored area does not extend into the flesh.

Possible Confusion:

Lenticel Spot; Bitter Pit; Storage Scald; Ammonia injury.

Susceptible Varieties:

This disorder was first identified in Jonathan, but has also be observed in Gala, Golden Delicious, Fuji, Braeburn, Red Delicious, and Jonagold.

Possible Causes:

Advanced maturity at harvest; low calcium concentration; delayed post-harvest cooling; higher temperature excels appearence.


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Lenticel Blotch Pit

Symptoms:

Lenticel Blotch Pit appears as slightly sunken, dry lenticel spots that may may join to form blotches.

Possible Confusion:

Jonathan Spot; Bitter Pit; Lenticel Breakdown; Carbon Dioxide injury.

Susceptible Varieties:

Lenticel Blotch Pit has been observed on several varieties including: Fuji, Gala, Braeburn, Granny Smith, Golden Delicious, Red Delicious, Honey Crisp, and Cameo.

Possible Causes:

This disorder is thought to be caused by low calcium concentrations and increased by delayed harvest.

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Storage Disorders - External & Internal

Superficial Scald

Superficial Scald

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Symptoms:

Appearance and severity depend on the variety of apple. Effected fruit show a browning of the skin, most noticeable on the uncolored (shaded) side of the fruit. Only the skin is affected; flesh may be firm and of eating quality. The margins between affect and normal skin are diffuse. Browning will develop rapidly upon removal from extended storage. Symptoms become obvious and will intensify when moved to a warmer temperature.

Possible Confusion:

Carbon dioxide (CO2) injury.

Susceptible Varieties:

Granny Smith and Red Delicious are most susceptible, but it has also been noted in Braeburn, Fuji, Pink Lady and Cameo.

Possible Causes:

Superficial scald is primarily due to picking the fruit too early followed by extended storage. Generally, this type of scald does not develop on fruit stored for a short period of time.


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Senescent Scald

Symptoms:

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 is on the sun exposed side of the fruit and on late harvested fruit.

Possible Confusion:

Superficial Scald.

Susceptible Varieties:

Golden Delicious and over-mature fruit.

Possible Causes:

Delayed harvest (over-mature); poorly cooled; stored too long.

Senecent Scald

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Core Flush

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Symptoms:

Core Flush manifests as a pinkish to dark brown discoloration emanating from the core with wedges extending into the flesh. The discoloration may be in a full circle around the core, or only partly around. The discoloration is between the outside of the core extending to inside the vascular bundles, but may extend beyond. The tissue is moist and softer than the unaffected flesh. Depending on severity, only the core area may be effected, or it may extend out to slightly below the skin. There may be no visible sign of Core Flush looking at the exterior of the fruit. The symptoms of Senescent Breakdown can be similar, but is usually associated with over-mature fruit and may develop early on in storage.

Possible Confusion:

Senescent Breakdown

Susceptible Varieties:

Especially Granny Smith, but also: Fuji, Braeburn, Golden Delicious, Red Delicious, Honey Crisp and Jonagold.

Possible Causes:

May be related to excessively low storage temperature.


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Watercore

watercore

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watercore RD

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Symptoms:

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, water core is externally visible by the appearance of translucent skin blotches on lighter pigmented apples, as shown in the Granny Smith apple above left and center, or as very dark patches on darker fruit, as seen on the Red Delicious apple above right. In mild cases water core will disappear (sorbitol re-absorbed) early on during cold storage. If severe enough, water core may develop into internal breakdown (watercore breakdown).

Possible Confusion:

Internal Browning

Susceptible Varieties:

Fuji and Red Delicious; as seen in: Granny Smith and Cameo.

Possible Causes:

Watercore develops in the orchard and is thought to be caused by high day temperatures followed by low night temperatures during the final maturation of the fruit when total soluble solids are high. Under these conditions sorbitol-rich cell sap leaks into the intercellular spaces.


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Lenticel Spot

lenticel spot

Symptoms:

Lenticel Spot appears as small brown lenticel spots with superficial necrosis. The condition is worse when stored under low relative humidity.

Possible Confusion:

High humidity cracking

Susceptible Varieties:

None specified

Possible Causes:

Lenticel spot has been observed in uncontrolled storage conditions, but the actual cause is unknown.

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Storage Disorders - Atmosphere

During controlled atmosphere (CA) storage it is important to maintain the correct levels of oxygen(O2) and carbon dioxide (CO2) to prevent fruit injury. If CO2 levels are too high or O2 levels are too low, or if both condition exist external and/or internal breakdown can occur. The severity and type of symptom depend on the levels and the length of time the fruit are exposed to the adverse conditions. Apple variety can also determine severity.

High Carbon Dioxide (CO2) Injury

Symptoms:

Both external and internal symptoms may occur. External damage symptoms resemble snowflake-like patches which may join to form one very large patch. Pictured to the right is an example external damage to Golden Delicious. The damage here is restricted to external browning with irregular (snowflake-like) margins. Internal symptoms appear as discolored areas within the vascular bundles. The tissue may be brown and develop pokets. A noticeable aroma of fermentation may be present when CA storage is opened, or the fruit is cut.

Possible Confusion:

Superficial Scald; CO2 injury doesn't continue to darken as does scald; Low O2 injury does not develop pockets.

Susceptible Varieties:

All varieties are susceptible.

Possible Causes:

CO2 levels too high during CA storage.

co2 injury

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Chilling Injury

chilling injury

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Symptoms:

Fruit stored below their freezing 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 may also develop. Fruit also may have a bitter taste and smell of fermenttaion upon cutting. Pictured here is an example of Red Delicious showing browning and skin translucency.

Possible Confusion:

Superficial Scald

Susceptible Varieties:

All varieties are susceptible.

Possible Causes:

Temperature too low during CA storage.


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Relative Humidity Disorders

Low Humidity Syptoms:

Shriveling can occur when the relative humidity during storage is too low as seen with the Gala apple shown above. This is caused by cellular desiccation.

High Humidity Symptoms:

Cracking is caused by too high relative humidity during storage. This is due to swelling of the cells. The Golden Delicious apple shown above cracked from the lenticels. However, often the cracking can be more dramatic with a single deep branching crack extending across the fruit.


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Sunburn Disorders

Sunburn Browning

Symptoms:

Sunburn Browning is the most common form of sunburn. The symptoms appear as a yellow, brown or dark tan spot on the sun exposed side of the apple.

Causes:

This disorder is induced by ultraviolet-B radiation from sun light along with temperature. Desiccated lenticels may also be present in the sunburned area depending on severity. Two examples of sunburn are shown above: Granny Smith (left) and Red Delicious (right).


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Sunburn Necrosis (formerly: Sun Scald)

Symptoms & Causes:

Sunburn Necrosis is heat-induced while the fruit is on the tree. Like Sunburn Browning it occurs on the sun exposed part of the fruit, but UVB is not a major factor. When the fruit surface temperature exceeds 126 degrees F for as little as 10 minutes, skin cell death occurs resulting in a dark brown or black (necrotic) spot that appears later. Cracking of the affected area is common. Shown above are three examples of Sunburn Necrosis: Granny Smith (left), Red Delicious (center), and Gala (right).


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Photo-oxidative Sunburn (formerly: Type 3 Sunburn)

Symptoms & Causes:

Apples that are suddenly exposed to sunlight after growing in shade, as would occur with hand thinning or late season pruning, may develop Photo-oxidative Sunburn (POS). Unlike the previously mentioned sunburn forms, POS is neither surface temperature, nor UV-B dependant. In addition to happening on the tree, it can also occur after harvest if apple bins are left sitting out in the sun in the field , on a truck, or at the packing dock. Symptoms of POS varies by severity, but in general,it manifests as a brown patch surrounded by bleached skin tissue. Two examples of POS are shown above: Granny Smith (left) and Red Delicious (right).


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References

Web Links

UC Davis Physiological Disorders Fact Sheets
Agri-Food Canada - Apple Disorders
Agri-Food Canada - Postharvest Disorders of Apples & Pears,
Market Diseases (& Disorders) of Apples, Pears, & Quince

 

Library References

V.F. Pierson, M.J. Ceponis & L.P. McColloch. 1971. Market Diseases of Apples, Pears, & Quince. Agricultural Handbook No. 376. USDA/ARS. Washington, D.C. USA. 131 pp illus. (Out of print. See link above for web copy.)

G.J. Eksteen & J.C. Combrink. 1987. Manual for the Identification of Post-harvest Disorders of Pome & Stone Fruit. Fruit & Fruit Technology Research Institute, Stellenbosch, South Africa. 42 pp illus. (Out of print, but some copies are around.)

M. Meheriuk & W.J. McPhee. 1986 (reprinted). Postharvest Handling of Pome Fruits, Soft Fruits, & Grapes. Agricultural Canada Publication 1768/E. Agriculture& Agri-Food Canada. Ottawa, CANADA. 51 pp illus.

B.B. Beattie, W.B. McGlasson & N.L Wade. 1989. Postharvest Diseases of Horticultural Produce Vol. 1.: Temperate Fruit.NSW Agriculture & Fisheries. CSIRO. AUSTRALIA. 84 pp illus.

A.L. Jones & H.S. Aldwinckle. 1990. Compendium of Apple & Pear Diseases. APS Press. St.Paul, MN. USA. 100 pp illus.

A. L. Snowdon. 1990. A Color Atlas of Post-Harvest Diseases & Disorders of Fruits & Vegetables. Vol. 1: General Introduction & Fruits. CRC Press, Inc. Boca Raton, FL. USA. 302 pp illus. (Applicable pages: 7-24; 30-33; 203-216.)

M. Meheriuk, R.K. Prange, P.D. Lidster & S.W. Porritt. 1994 (revised), Postharvest Disorders of Apples & Pears. Agricultural Canada Publication 1737/E. Agriculture& Agri-food Canada. Ottawa, CANADA. 67 pp illus.

M. Giraud, P. Westercamp, C. Coureau, J-F. Chapon & A. Berrie. 2001. Recognizing Postharvest Diseases of Apples & Pears. CTIFL. Paris, FRANCE. 100 pp illus. (French with English captions)

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