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Apples: Why Are Some Brown Inside (But look Good Outside)

Have you bought apples (especially Fuji) that look great and when you get them how and cut them open, you find they are brown or have brown spots inside? This is becoming a more common problem, and unscrupulous (or simply incompetent) middlemen may be at the heart of it. It has to do with how the apples are stored after they are harvested.

Storage-Caused Browning, CO2 damage:

If the apple looks great on the outside, no brown spots, blemishes, etc. – but is brown inside

In this case, the most common problem is due to how the apples were handled in storage after being harvested. UC Davis tells us:

Internal browning, thought to result from CO2 injury, has been reported in Fuji, Cox’s Orange Pippin, Braeburn and Jonathan apples. The disorder is associated with later harvested, large, and overmature fruit and with CO2 concentrations in storage. Higher concentrations of CO2 result in greater incidence and severity of internal browning. Incidence and severity of this disorder varies season to season and orchard to orchard. The reasons for this variability are unknown but some have suggested an association with cool, wet weather and high nitrogen fertilization

This makes sense to me. I bought 3 bushels of Fuji’s in late September 2019 at the farmers market. They were exceptionally large (the size of softballs or grapefruit), and looked and felt perfect on the outside. When I cut them out, 1/3 to 1/2 of them looks like this:

When you look at this photo, understand that I took this picture with 90 seconds of cutting these apples. This is NOT due to air exposure, where apples brown after being cut and exposed to oxygen. That takes longer than a minute or due, this is how the apples look the moment they are cut open.

I cut a piece of the white portion of one of these apples and tasted it. It had a mealy, mushy texture and tasted bland.. not bad, but simply flavorless.

The degree of browning varied from faint brown to quite dark.

Firm Flesh Browning

Empire and McIntosh apples and presumably, Fuji, are susceptible when they are stored for too long in cold temperatures. It looks a lot like the browning caused by CO2issues (shown above), affecting the core and flesh. A key difference is there is no clear boundary between the afflicted flesh and the undamaged areas; they blend together. U of Maine says that it occurs more frequently when the apples are harvested late (for the variety) and a storage compound, 1-MCP, is used.

Soggy Breakdown caused by too cold storage

The University of Maine has a page that shows and explains several apple browning problems, including “Soggy Breakdown.

They tell us:

Soggy breakdown is an internal chilling injury that develops when susceptible varieties of apple are stored at a temperature below their tolerance. For Honeycrisp, temperatures below 37ºF can induce this disorder. Browning develops in the outer cortex. Severity of symptoms range from small brown spots in the cortex to a complete ring of browning around the entire apple that usually does not extend to the skin. There is usually ring of unaffected tissue just inside the skin. In Honeycrisp, it often co-occurs with soft scald. Conditioning the fruit before placement in cold storage does not consistently prevent soggy breakdown and in some cases, can make it more severe. It is recommended that Honeycrisp be stored at temperatures of 37 to 38ºF.

Ordinary Browning

Compare the CO2 issue above with ordinary browning , or “enzymatic browning.” When you cut open an apple, the flesh is first now exposed to oxygen. An enzyme in the apple called polyphenol oxidase (PPO) starts to oxidize compounds in the apple’s flesh called polyphenols.

The oxidized polyphenols are transformed into “o-quinones” , which then react with amino acids in the apples to produce the brown color.

Some apple varieties have more of the enzymes and the polyphenols which means they brown more. Some new varieties have been bred to have lower levels of these compounds and stay white after cut. The browning does not affect flavor or even texture. Sure, if you leave cut apples out for a day, that would, but that’s due to actual rotting, not a simple enzymatic color change.
This enzymatic browning also occurs in other fruit, most noticeably bananas, pears and eggplants.

If you want to keep enzymatic browning to a minimum, see this page for simple tips that work!

At right is a photo of ordinary air-exposed browning, top a fresh cut Fuji apple and bottom the same slice, 20 minutes later.

See this page for a time lapse set of photos showing how an apple slice browns once cut.

Both slices are perfectly fine to eat!

Other causes of apple browning problems

Apple maggot damage

If a female apple maggot lays an egg in a growing apple, it leaves a dimple or small spot where the egg is laid. Once the egg hatches, the maggot eats some of the apple flesh. This causes brown spots inside the apple. The apple maggot leaves the apple (so you won’t find one inside, just the brown damaged flesh).

Bitter Pit

Bitter pit shows up as recessed small brown divots in the outside surface of the apple, sort of like the dimples on a golf ball, but dark brown in color. There are also brown spots inside the apple’s flesh. It is caused by a calcium deficiency in the fruit and can appear while the fruit is still on the tree or appear within the first month or two of cold storage. Most susceptible varieties include Honeycrisp, Northern Spy, Gravenstein, Grimes Golden, and Baldwin and to a lesser degree Golden Delicious. Red Delicious, Gala, and Winesap and more resistant. See this page for photos.

Soft scald

Another chilling disorder that affects Honeycrisp, Golden Delicious and McIntosh apples when they are stored at temperatures below their tolerance. It looks like a blister or light brown discoloration of the skin and then can become dark, affect the flesh beneath and eventually produce fungal decay.

Superficial scald

This damage DOES affect the outside, causing visible browning when certain apple varieties are stored longer than three months in cold storage. Brown splotches develop on the green side of the apple, and will continue to grow in size when the apple is held at warm temperatures. It is also associated with early harvest date. Cortland, Red Delicious, McIntosh, and Granny Smith are most susceptible.

Senescent breakdown

This is simply due to the apple being too old, stored for too long. How long is too long varies from one variety to the next. Fuji’s store well, but Macoun shows signs with 2 months. All varieties will eventually develop senescent breakdown if stored long enough. Commercial apple stores use the proper temperature (which is specific top each variety), harvesting at proper maturity, a controlled atmosphere (e.g., CO23 levels) and, in some cases the use of a compound called 1-MCP to delay it.

What can you do with browned apples?

If the apples look ok when you cut them, and start to brown only after being cut; they’re fine – THAT IS NORMAL!

But for the apples that are brown inside when you cut them open, there’s not much you can do. I wouldn’t use them,, First off, they taste awful! They may not be harmful to eat, but what’s the point if they taste bad?

How can you prevent browning of apples at home?

The normal browning CAN be easily reduced or eliminated; see this page.

  1. University of California at Davis –
  2. University of Maine Cooperative Extension – Lots of good example photos here and explanations of causes
  3. University of Minnesota – Apple Maggots
  4. Pacific Northwest Pest Management Handbooks – Bitter Pit

Apples: Dark spots are signs of bitter pit

PUBLISHED: 08:49 27 February 2012

Martyn Davey

Answer:

This problem is quite common and seems to be worst in Bramley apples in storage. The problem here is called ‘bitter pit’, which is a disorder that causes dark spots on apples late in the season or in storage. This condition is related to lack of calcium in fruit and is often as a result of dry soil conditions.

Not that bitter pit is a disorder, not a disease. It is caused by low levels of calcium in the fruit and it is more common after hot, dry summers. It can usually be reduced or, sometimes, prevented with good cultivation practices.

Bitter pit is caused by low levels of calcium in the fruit and poor distribution of calcium within the tree during fruit development.

However, it is rarely due to a deficiency of calcium in the soil and can even occur in trees growing on chalk. Bitter pit is more usually connected with an irregular supply of water, which prevents calcium being taken up and circulated around the tree. Problems are generally worse in seasons when there are wide fluctuations in rainfall and temperature and a shortage of water to trees at critical times during fruit development.

It is also worth noting that excessive use of nitrogen, potassium and magnesium fertilisers can cause or worsen the problem.

Low levels of calcium are also thought to be a cause of discolouration of pear and quince flesh and a susceptibility to translucent, water-soaked areas in the flesh of apples (a problem known as ‘water core’).

Small sunken pits develop on the surface of the fruit and the flesh beneath the pits is discoloured and dry. In severe cases, brown areas of tissue are scattered throughout the flesh of an infected apple and it takes on an unpleasant, bitter taste.

Symptoms can appear from when the fruits are about half developed until they are harvested or, as is often the case, do not develop until the fruits have been stored.

It is more common on young, vigorouslygrowing trees – especially those fed heavily with nitrogenous fertilisers – but it can also develop on fairly old trees, especially culinary cultivars with large fruit.

Some cultivars are particularly susceptible. These include the likes of Bramley’s Seedling, Cox’s Orange Pippin, Egremont Russet, Hamling’s Seedling, Meridian, Merton Worcester, Newton Wonder and Warner’s King.

Some cultivars show some resistance to bitter pit. Jonagold and Gala, for example, appear unaffected.

Correct feeding and watering to maintain steady growth throughout the growing season is the key to reducing problems with bitter pit. Use a general-purpose, balanced fertiliser and avoid excessive feeding with nitrogenous (such as sulphate of ammonia) or potassium-rich (such as sulphate of potash) fertilisers. Install irrigation to maintain a uniform supply of water throughout dry periods and mulch to retain moisture in the soil around the tree.

Summer pruning of apple trees reduces the leaf area, which helps to control the vigour of trees and redirects calcium to fruits as well as foliage. However, avoid heavy pruning.

Foliar sprays of calcium nitrate can be applied from mid-June to mid-September to increase the concentration of calcium within the developing apples. Follow the manufacturer’s advice on rates and spraying intervals and never mix with fungicides or insecticides. Add a wetting agent or a few drops of detergent to help products adhere to leaves. Spray only when temperatures are below 21°C (70°F) and only in the evening to avoid ‘russeting’ (where apple skins develop rough, brownish patches).

A very few cultivars, notably Bramley’s Seedling, are sensitive to calcium nitrate so spray with a half-strength solution.

Fruit should be left on the tree until it is fully ripe. Unripe fruit are more likely to have low calcium levels.

Where the brown patches only appear near the skin, they can be removed by peeling the fruit. Bad cases may make the flesh inedible.

Try to cook up affected fruit immediately after harvest before the disorder progresses (sugar should disguise any bitterness).

Fruit from trees with a recurrent bitter pit problem can be frozen, rather than stored, to prevent the disorder developing.

•This article was first published on November 26, 2011.

Cooperative Extension: Tree Fruits

Storage Disorders

Apple and pear flesh and skin can turn brown during storage. When browning occurs that is a natural process of aging rather than by infection from fungi, it is a disorder. Many types of disorders lead to loss of marketability, and vary with the relative maturity at harvest. Conditions in the orchard, such as fertility, and the variety can predispose fruit to certain disorders. In stone fruit, storage disorders are primarily due to cold temperatures and are grouped together as chilling injury.

Bitter pit symptoms in Honeycrisp apple.

Bitter pit is a disorder that is partly caused by calcium deficiency in apple. It begins in the orchard, but the browning does not develop until after harvest. Small, sunken spots that are light or dark brown and located near the blossom end of the fruit are characteristic of this disorder. The browning can extend slightly into the flesh. Early harvest, high levels of nitrogen fertility, light crop load, and large fruit size increase its incidence. Honeycrisp is highly susceptible to bitter pit, so early harvest should be avoided in this variety. Jonagold, Granny Smith, and Cortland are also susceptible, but repeated foliar application of calcium products can prevent bitter pit in most cases. For Honeycrisp, foliar calcium applications should begin at petal fall and continue to harvest.

Superficial scald in apple.

Superficial scald of apple is a skin browning disorder that develops in some varieties when they are cold stored longer than three months. Brown splotches develop on the green side of the apple, and will continue to grow in size when the apple is held at warm temperatures. It is also associated with early harvest date. Cortland, Red Delicious, McIntosh, and Granny Smith are susceptible and should be treated with an anti-scald agent prior to placement in cold or controlled atmosphere storage. Diphenylamine (DPA), 1-MCP and ethoxyquin are scald inhibiting agents labeled for use on apple. 1-MCP is not effective for preventing superficial scald in Cortland, so this variety should receive DPA when stored longer than three months. Gala, Honeycrisp, Golden Delicious, Empire, and SnowSweet are not susceptible to superficial scald.

Soggy breakdown symptoms in Honeycrisp apple.

Soggy breakdown is an internal chilling injury that develops when susceptible varieties of apple are stored at a temperature below their tolerance. For Honeycrisp, temperatures below 37ºF can induce this disorder. Browning develops in the outer cortex. Severity of symptoms range from small brown spots in the cortex to a complete ring of browning around the entire apple that usually does not extend to the skin. There is usually ring of unaffected tissue just inside the skin. In Honeycrisp, it often co-occurs with soft scald. Conditioning the fruit before placement in cold storage does not consistently prevent soggy breakdown and in some cases, can make it more severe. It is recommended that Honeycrisp be stored at temperatures of 37 to 38ºF.

Soft scald symptoms in Honeycrisp apple at an early stage of development.

Soft scald symptoms in Honeycrisp apple at an advanced stage of development.

Soft scald is a chilling injury disorder that occurs when susceptible varieties of apple are stored at temperatures below their tolerance. Soft scald develops first as a light brown discoloration of the skin. It may extend into the flesh and closely resemble a bruise. Eventually, fungal decay will occur in the affected areas. Severity ranges from small spots to nearly the entire surface of the apple. Honeycrisp is highly susceptible to this disorder and can succumb at temperatures normally used for cold storage. Other varieties that can develop soft scald include Golden Delicious and McIntosh, but this rarely occurs at temperatures that are commonly used for apple storage. Late harvest also worsens symptoms.

Senescent breakdown in an advanced stage of development.

Another consequence of late harvest is the loss of apples to senescent breakdown, an aging disorder. Some varieties, such as Macoun, develop it after a few months in cold storage whereas other varieties, such as Red Delicious, can be stored several months without an occurrence. However, all varieties will eventually develop senescent breakdown if stored long enough. Harvest at the right maturity for the storage duration, cold temperatures, and controlled atmosphere storage are the most effective methods of delaying its occurrence. Application of 1-MCP is also effective in delaying it.

Lenticel breakdown in apple resembles bitter pit but is not isolated to the blossom end of the fruit. Brown circular areas develop over some of the lenticels. It is associated with a late harvest and long storage periods, but the exact cause is unknown. Honeycrisp is prone to this disorder.

Firm flesh browning in an apple.

Firm flesh browning occurs in Empire and McIntosh apples when stored for long durations at cold temperatures. It occurs more frequently with late harvest and the use of 1-MCP. Light browning occurs in the core and cortex. The flesh is discolored in a general manner with no distinct boundary between afflicted and healthy tissue. It is a difficult disorder to prevent since quality loss can occur if storage temperatures are above 35ºF, but the chance for browning increases at temperatures below this. The most effective method of prevention is harvesting at an early maturity for apples that will be stored longer than four months.

Vibrational bruises can occur in some varieties of plum such as Shiro. Shortly after transporting plums from the orchard, brown circles appear on the skin of sensitive varieties. When transporting plums from the orchard to the packing house or farm market, take steps to reduce movement of fruit in harvest containers.

Chilling injury in stone fruit manifests itself in a number of ways. Flesh color can change from normal to brown and can become translucent. In some cases, the flesh becomes stringy or mealy.

Vibrational bruising on Shiro plums.

Chilling injury in Shiro plums.

What Are Those Tiny Spots on Apples?

Following a big win in the Super Bowl, World Series, NBA Finals, or any other major sporting event, fans want to get their hands on championship merchandise as quickly as possible. To meet this demand and cash in on the wallet-loosening “We’re #1” euphoria, manufacturers and retailers produce and stock two sets of T-shirts, hats, and other merchandise that declare each team the champ.

On Super Bowl Sunday, that means apparel for the winner—either the San Francisco 49ers or the Kansas City Chiefs—will quickly fill clothing racks and gets tossed to players on the field once the game concludes. But what happens to the losing team’s clothing? It’s destined for charity.

Good360, a charitable organization based in Alexandria, Virginia, handles excess consumer merchandise and distributes it to those in need overseas. The losing team’s apparel—usually shirts, hats, and sweatshirts—will be held in inventory locations across the U.S. Following the game, Good360 will be informed of exactly how much product is available and will then determine where the goods can best be of service.

Good360 chief marketing officer Shari Rudolph tells Mental Floss there’s no exact count just yet. But in the past, the merchandise has been plentiful. Based on strong sales after the Chicago Bears’s 2007 NFC Championship win, for example, Sports Authority printed more than 15,000 shirts proclaiming a Bears Super Bowl victory well before the game even started. And then the Colts beat the Bears, 29-17.

Good360 took over the NFL’s excess goods distribution in 2015. For almost two decades prior, an international humanitarian aid group called World Vision collected the unwanted items for MLB and NFL runners-up at its distribution center in Pittsburgh, then shipped them overseas to people living in disaster areas and impoverished nations. After losing Super Bowl XLIII in 2009, Arizona Cardinals gear was sent to children and families in El Salvador. In 2010, after the New Orleans Saints defeated Indianapolis, the Colts gear printed up for Super Bowl XLIV was sent to earthquake-ravaged Haiti.

In 2011, after Pittsburgh lost to the Green Bay Packers, the Steelers Super Bowl apparel went to Zambia, Armenia, Nicaragua, and Romania.

Fans of the Super Bowl team that comes up short can take heart: At least the spoils of losing will go to a worthy cause.

An earlier version of this story appeared in 2009. Additional reporting by Jake Rossen.

All images courtesy of World Vision, unless otherwise noted.

Causes of apple skin spot revealed by study

“Previous report have suggested that apples are particularly susceptible to skin spot if they are poorly colored, from dense canopies, grown in wet years, or harvested late,” noted Moritz Knoche, corresponding author the study published in HortScience. Knoche explained that skin spot comprises patches of small, brownish spots that are caused by the death of individual epidermal and hypodermal cells underlying microcracks in the fruit cuticle. A research team investigated the relationship between surface water on fruit, the formation of microcracks in the fruit cuticle, and the severity of skin spot in ‘Elstar’ apples grown under rain shelters. During the study, fruit surface wetness was maintained by overhead sprinklers installed above apple trees grown under a plastic rain shelter (deployed between 5 and 134 days after full bloom). The experiments featured four different wetness periods.

Analyses showed that increasing fruit surface wetness by overhead sprinkling increased both the severity of skin spot and the severity of cuticular microcracking. “Most skin spots and microcracks were already present by harvest time and before storage,” the researchers noted. “However, the severities of both increased significantly during storage. Surface wetness between 14 and 44 days after first bloom had no effect on the severity of skin spot compared with dry, control fruit but markedly increased the surface area percentage of the skin that was russeted.” The scientists said there was essentially no skin spot or russeting when the apple surfaces were kept dry.

The researchers also studied the severity of skin spot under standard orchard conditions over a 9-year period and discovered that the disorder was positively correlated with the number of rainy days during the period. “In relation to the severity of skin spot, surface wetness is better described by the number of rainy days than by the cumulative rainfall amount,” they explained. “A commercially critical skin spot score of 2 is predicted if there are more than 44 rainy days between August 1 and harvest for control fruit, and if there are more than 34 rainy days for 1-methylcyclopropene-treated fruit,” Knoche said.

The results demonstrated that surface wetness results in the formation of microcracks in the cuticle, which in turn is a prerequisite for the formation of skin spot. Skin spot in ‘Elstar’ apple arises as a result of microcracking, and this is a result of late-season surface wetness.

Knoche added that russeting and skin spot may both be viewed as a wound reaction of the fruit. “The initial event, the crack in the cuticle, is identical (both water induced); however, the subsequent events differ. In russeting, a periderm is formed in the young and developing fruit as a protective layer. In skin spot, no periderm is formed, but lignin incrustration of the cell walls seals the portion of the tissue underlying the crack off. The “damage” (crack) is contained. Why apple fruit does not respond with russeting later in development nobody knows.”

CORVALLIS – Wet weather, which is bound to come in the weeks ahead, builds potential for apple scab, a fungal disease of apples.

The apple scab disease fungus overwinters on dead apple leaves and fruit left on the ground, explained Ross Penhallegon, horticulturist for the Oregon State University Extension Service. During spring moisture, scab spores are forcibly discharged and ride air currents to infect developing leaves and fruit of apples. All outer parts of unopened fruit buds are highly susceptible to scab. As the fruit matures it is much less susceptible.

The first visible symptoms of apple scab in the spring are pale, water-soaked spots the size of a pinhead on the new leaves. These spots enlarge, become darker and smoky colored. Later, the spots turn brownish-black color. Spots may be any shape, but tend to be circular, Penhallegon said. Diseased leaves may be curled, distorted and drop off early. Heavy infections can defoliate and weaken your apple trees.

On the fruit, the symptoms of scab include small raised brown or black circular areas (scabs). The skin breaks later in the season and the exposed tissue turns velvety brown or black. As the fruit enlarges, the scab spots become brown and corky. To help control apple scab, Penhallegon recommends:

  • Grow scab-resistant cultivars of apples. Apples with good resistance include Akane, Chehalis, Liberty, Prima and Tydeman Red.
  • Apply nitrogen to leaves that have fallen to the ground in the fall to enhance decomposition of fallen leaves and make them more palatable to earthworms. Hand-apply a liquid fish solution or 16-16-16 fertilizer to help with the decomposition.
  • Shred fallen leaves in the fall with a mower to help speed up decomposition.
  • Prune your apple trees to open up branching and allow more air circulation.
  • When watering your apple trees, avoid getting foliage wet.
  • Apply dolomitic lime in the fall, after leaf drop, to increase pH and to help reduce fungal spores in the spring.
  • Spray fungicide – Bonide Captan, wettable sulfur, summer lime sulfur or Spectracide Immunox – when temperatures are above 60 degrees and the leaves or blooms are wet.

For more information, consult the Extension publication on Apple Scab.

MORE OREGON GARDENING ADVICE

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  • Will grass grow in this soggy spot?
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Fruit Physiological Disorders

Bitter Pit. Apple, Granny Smith Occurrence
Apple

Importance
Bitter pit reduces the fresh market quality of fruit. It was first described in Germany and is recognized as an abiotic disorder found in all areas of the world where apples are grown. This physiological disorder is influenced by climate and orchard cultural practices.
Symptoms
Small brown lesions of 2-10 mm in diameter (depending on the cultivar) develop in the flesh of the fruit. The tissue below the skin becomes dark and corky. At harvest or after a period of cold storage the skin develops depressed spots on the surface. These most often start to appear as water soaked spots on the skin near the calyx. These spots generally turn darker and become more sunken than the surrounding skin and are fully developed after one to two months in storage.

Fruit located on vigorous, leafy, upright growing branches have a greater potential to develop bitter pit than does fruit that develops from spurs or on horizontal wood near the tree’s main frame. Young trees that are just coming into bearing are the most susceptible. Immature fruit are more susceptible to bitter pit than fruit harvested at the proper harvest maturity. Older trees, which are less vigorous and produce larger crop loads, reduce their susceptibility to bitter pit except in the very sensitive cultivars.

Highly Susceptible Cultivars
Granny Smith, Yellow Newtown, Jonathan, Golden Delicious (California), Gravenstein, Red Delicious (California), Baldwin, Boskoop, Bromley’s Seedling, Cleopatra, Cox’s Orange Pippin, Grimes Golden, Merton, Rhode Island Greening, Worcester, Stayman (Canada), Sturmer, White Winter Pearmaine, Prima Starking, Starkrimson, Marigold, Northern Spy, and York Imperial.

Physiology
Initiation of symptoms may begin four to six weeks after petal fall when affected tissues have a higher rate of respiration and ethylene production. This is a period of greater protein and pectin synthesis with greater migration of organic ions into the affected areas. Affected areas retain starch grains not seen in healthy tissue. A mineral imbalance in the apple flesh develops with low levels of calcium and relatively high concentrations of potassium and magnesium. Low levels of calcium impair the selective permeability of cell membranes leading to cell injury and necrosis. Other explanations for the cause of bitter pit include the dissolution of the middle lamellae by oxalic and succinic acid, and changes in proton secretion and potassium permeability.

Control
Cultural practices that reduce the incidence of bitter pit are annual bearing, moderate tree vigor, smaller fruit size, calcium sprays, summer pruning and harvesting mature fruit. Avoid nitrogen and magnesium summer sprays, fertilizer treatments that result in lowering the soil pH or induce excess vigor, and fluctuating soil moisture. Early thinning and over thinning can increase bitter pit. Do not over dormant prune, which would result in a light crop and large fruit. Summer sprays of calcium chloride(CaCl2), calcium nitrate and/or a postharvest dip in a calcium solution are recommended. Both CaCl2 and Ca(NO3)2 summer sprays are effective at reducing the incidence of bitter but the response varies with the cultivar and both may cause russeting and leaf burn under certain conditions. In California, apply at least three sprays at one month intervals beginning in mid-June. Use 20 pounds of Ca(NO3)2 per acre in 400 gallons of water or 12 pounds of CaCl2 per acre in 400 gallons of water. Apply sprays under conditions of rapid drying to prevent russeting. Orchards with a history of severe bitter pit should receive four to six sprays or more at two week intervals. Fruit coverage is mandatory. Postharvest dips before storage may reduce bitter pit symptoms. Use 2-3% by weight CaCl2 in the drench water. Calcium dips can cause fruit injury, follow the label recommendations carefully.

Preharvest sampling for bitter pit is possible. Two weeks before harvest select large fruit from upright limbs of light cropped, vigorous trees. Dip the fruit in a solution of 2,000 ppm ethephon in water (about 1½ teaspoons of ethephon to one gallon of water) to hasten the ripening process. Hold the fruit for two weeks at room temperature. If bitter pit develops, delay the harvest as long as possible. Cool the harvested fruit as soon as possible and delay the packing for at least four weeks. The delay will allow the bitter pit to fully develop. The affected fruit is then removed during the packing process.

Integrated Pest Management For Apples and Pears. University of California, Division of Agriculture and Natural Resources, Publication 3340, 1991. ISBN 0-931876-94-X, Library of Congress Catalog Card No. 91-65337.

Bitter Pit of Apples. University of California Cooperative Extension Publication, Division of Agricultural Sciences, Leaflet 2712, 1975.

What Is Apple Bitter Pit – Learn About Treating Bitter Pit In Apples

“An apple a day keeps the doctor away.” So the old adage goes, and apples, indeed, are one of the most popular of fruit. Health benefits aside, apples have their share of disease and pest issues that many growers have experienced, but they are also susceptible to physiological disorders. One of the more common of these is apple bitter pit disease. What is apple bitter pit in apples and is there an apple bitter pit treatment that will get bitter pit under control?

What is Apple Bitter Pit Disease?

Apple bitter pit disease should more properly be referred to as a disorder rather than a disease. There is no fungus, bacteria or virus associated with bitter pit in apples. As mentioned, it is a physiological disorder. This disorder is the result of a lack of calcium in the fruit. Calcium may be plentiful in the soil and in the leaves or bark of the apple tree, but lacking in the fruit.

The symptoms of apple bitter are mildly water-soaked lesions on the skin of the apple that become evident beneath the skin as the disorder develops. Under the skin, the flesh is dotted with brown, corky spots that indicate tissue death. The lesions vary in size but are generally about ¼ inch across. Apples with bitter spot do indeed have a bitter flavor.

Some apple varieties are more prone to bitter spot than others. Spy apples are frequently affected and with the correct conditions, Delicious, Idared, Crispin, Cortland, Honeycrisp and other varieties may be afflicted.

Apple bitter pit disease may be confused with stink bug damage or lenticels blotch pit. In the case of bitter pit disorder, however, the damage is confined to the lower half or calyx end of the fruit. Stink bug damage will be seen throughout the apple.

Apple Bitter Pit Treatment

In order to treat bitter pit, it’s important to know the genesis of the disorder. This might be a bit difficult to pinpoint. As mentioned, the disorder is the result of a lack of calcium within the fruit. A number of factors can lead to insufficient calcium. Bitter pit control will be the result of cultural practices to minimize the disorder.

Biter pit may to be evident at harvest but as the fruit is stored it may manifest, especially in fruit that has been stored for some time. Since the disorder develops when apples are stored for lengthy periods of time, if you are aware of a previous problem with bitter pit, plan to use your apples as soon as possible. This brings up the question “are apples with bitter pit edible.” Yes, they may be bitter, but they won’t harm you. Chances are good that if the disease is evident and the apples taste bitter, you won’t want to eat them, however.

Large apples from small crops tend to be more prone to bitter pit than apples harvested during heavy crop years. Fruit thinning results in larger fruit, which is often a desirable thing but since it may foster bitter pit, apply a calcium spray to control bitter pit.

Excessive nitrogen or potassium seems to coincide with bitter pit as does fluctuating soil moisture; mulch around the tree with a low nitrogen material to help retain moisture.

Heavy dormant season pruning increases shoot growth because it results in higher nitrogen levels. Heavy shoot growth leads to a competition between fruit and shoots for calcium which may result in bitter pit disorder. If you plan to prune the apple tree severely, reduce the amount of nitrogen fertilizer provided or, better yet, prune judiciously each year.

Need help with what to do in your garden?

Q I’ve been told that my apples have bitter pit. What is this?

A Bitter pit is a physiological disorder that only affects apples. It causes small, dark, slightly sunken patches on the skin and brown specks in the fruit.

Caption: Bitter pit causes marks on the skin and flesh

Q What causes bitter pit?

A A lack of calcium, perhaps because there’s not enough calcium in the soil, but, more often, it’s linked to lack of water or a very heavy fruit crop. These two factors can mean that not enough calcium is carried to the fruit, so it doesn’t develop properly.

Q Can I still eat apples affected by bitter pit?

A Yes, although if the bitter pit is extensive the fruit may be unpalatable. Fruit with bitter pit does not store well, as the damaged areas tend to rot.

Q Can bitter pit be cured?

A You can’t cure it once the apples are damaged, but you can help to prevent it in future seasons. First, try improving the tree’s water supply. Mulch in spring, when the soil is moist but not saturated. Our tests show that black polythene or grass clippings are very effective. If you dislike their appearance, cover with chipped bark.

In very dry spells, when soil is still dry 30cm down, water at the rate of 20-50 litres weekly per tree, depending on the size of the tree. Repeat this until there is a good downpour. Combine this with summer pruning and fruit thinning to reduce the size of the crop.

If your soil is acid, add enough lime to raise the pH to about 6.5. If this doesn’t do the trick, spray the tree with calcium nitrate solution (50g per 5 litres) every three weeks from late July to late October.

Q Does bitter pit happen to all apples trees every year?

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