Why do apples and pears rot during storage

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Why do apples and pears rot during storage
Why do apples and pears rot during storage

Preservation of apples and pears in winter, due to various diseases that may occur while the fruit is still on the tree, affects the freshness. By nature, they are divided into physiological, caused by internal tissue process disorder, and infectious.

So, there is no need to get angry because apples and pears have holes somewhere, rot somewhere, or ugly shape somewhere. You need to make conclusions in the next year to prevent these diseases. This article will help you in this regard.


PHYSIOLOGICAL DISEASES OF APPLES AND PEARS

Bitter spots (subcutaneous spots)

Detected on the tree or after 1.5-2 months of storage. It has been noted that pitting is more often seen on large fruits grown in the shade.

On the fruit, small irregular, round spots appear, up to several millimeters deep, green in yellow apples and dark purple in red apples; most often on one side, around the calyx. Over time, the spots turn brown and the affected area becomes spongy and bitter.

Causes of the disease may include.

  1. Potassium deficiency.
  2. Excessive pruning.
  3. Excessive doses of nitrogen.
  4. High humidity in spring and summer.
  5. Untimely harvesting of fruit.

Sunburn (epidermal burns, skin browning)

May be found at harvest or may appear in the 4th or 5th month of storage. Fruits harvested early are more affected by sunburn than those harvested at the optimal time for the variety.

It appears as light brown or blue-green spots, which over time become covered by brown spots. Gradually, the infested area expands and can cover not only the entire surface of the fruit but also the underlying tissues. The fructification will rot.

The causes of superficial burns are.

  1. Clumped crowns.
  2. Potassium deficiency or phosphorus deficiency.
  3. Excess nitrogen.
  4. Excessive humidity in late summer and early fall.
  5. Excessive temperatures at maturity.

In storage, the manifestation of these symptoms can be triggered by temperature differences or high humidity.


Wet scald (low temperature)

This physiological disorder of apples and pears is manifested in storage by non-compliance with the temperature regime, more precisely, under low-temperature conditions. It is manifested as irregularly shaped brown, deepened spots or banded areas with clear borders. The flesh under the spots turns watery and brown.

Causes of scald onset.

  1. Harvesting ripe fruits in cold weather.
  2. A combination of poor air circulation, high humidity, and low storage temperature.

Vitrification (puffing)

Fruits with glassy capillaries: This occurs when part of the fruit’s cell wall breaks down, causing the space between cells to fill with cytosol. Fruits suffering from vitreous infection lose their flavor and taste unpleasant. It is caused by the difference in osmotic pressure between the cells and the intercellular space, resulting in the rapid conversion of starch into sugar.

Causes of the development of vitreous apples and pears.

  1. Potassium deficiency.
  2. Late harvesting of the fruit, coinciding with cold weather.
  3. Improper storage conditions – high humidity, combined with low temperature, and lack of air circulation.

Puffiness (bloating, powdery decomposition of the fruit)

The fruit shows puffiness, a tendency to lose its regular texture. Affected fruits become loose, flabby, and burst, sometimes to the core.

Causes.

  1. High doses of nitrogen have been applied.
  2. The tree is deficient in calcium.
  3. Late harvest.

Nucleus browning of apples and pears

Apples and pears: this disease occurs due to excessive storage time. It manifests itself as browning of the fruit tissue around (sometimes together with) the seed chamber. In appearance, this process is not reflected.

The causes of this phenomenon are.

  1. Excessive moisture in the fruit at maturity.
  2. Long storage time.
  3. Storage conditions (poor ventilation, high or very low temperatures).

Withered fruit

Occurs when the fruit loses up to 5% of its weight. It usually occurs when apples and pears are stored improperly – at too high a temperature or too low a humidity. In addition, late harvesting is one of the reasons for the occurrence of this disease.


Browning of the flesh

There are two reasons for the onset of the disease in apples and pears: the natural aging of apples and pears after a long storage period, and the low storage temperature. The appearance of this phenomenon is the discolored area where the flesh is sharply separated, sometimes including the seed chamber. At an advanced stage, large, indistinct blue-green spots can also appear on the skin.

Causes of the disease include.

  1. Calcium deficiency.
  2. High doses of nitrogen.
  3. Late harvest.

HOW TO STORE APPLES AND PEARS WITH PHYSIOLOGICAL DISEASES?

In most cases, physiological problems of fruit storage are caused by improper nutrition from the plant. To prevent this, you need to follow the agricultural techniques for growing fruit crops: correction of nutritional deficiencies, competent fertilization, regular watering, proper pruning, and timely harvesting.

For spring calcium deficiency, as early as 10 days after the completion of the flowering period and at an interval of 15 days, it is recommended to treat the foliage with preparations containing calcium for one cycle (4 to 8 times).

Apples and pears with physiological diseases are helped to preserve freshness by appropriate fruit preparation and late storage conditions: timely harvesting, rejection of fruit with disease symptoms, immediate storage, temperature, and humidity conditions during storage (please read the end of the article).


MICROBIAL DISEASES OF APPLES AND PEARS

Microbial diseases of apples and pears
Microbial diseases of apples and pears

This category includes fruit lesions related to fungal diseases – various kinds of rots.


Fruit rot (Candida rot, candidiasis)

The disease is caused by the fungi Monilinia fructigena and Monilinia laxa that attack apples and pears already on the tree through mechanical damage. Often the disease is already present in the orchard. If not, under improper storage conditions.

One type of disease begins as a small, rapidly growing brown spot that gradually covers the entire surface of the fruit. Concentrically arranged mats of photosynthetic substrates form on its surface as the borders of the decayed tissue expand. Over time, the affected fruit dries out and takes on a mummified appearance. If the disease manifests itself in the depot, it is transmitted to neighboring fruits.

If the infection with the fungus occurs late, or when the fruit is ready to be shipped, the second type of disease development occurs – blackening of the fruit. The entire surface of the apple (pear) gradually turns black (becomes blue-black), becomes shiny, smooth, and leathery. The appearance of this disease often does not see spores, so neighboring fruits are not infected.

Ciliopathy is easily recognized by several other symptoms: the flesh softens, becomes spongy and brown, and acquires a sour-sweet taste.


Bitter rot (Colletotrichum rot, anthracnose)

The most widespread disease. It is caused by several fungi at the same time: The rots are caused by three species of fungi, mainly G. album and G. perennans, and Colletotrichum spp. (formerly G. fructigenum). Fructigenum).

Fungal spores attack the tissues of apples and pears while the tree is still moist, through lenticels that have not yet sprouted. They remain in a dormant state until the fruit is fully ripe. Development begins during storage. Symptoms can vary depending on which fungus is causing the infestation.

  1. On well-ripened fruit, the disease appears as a series of closely spaced, round, well-defined, depressing brown spots with light-colored concentric microspore mats.
  2. Sharp brown spots with rapid depressions around the circumference appear. The sporangium of the fungus is located under the skin and will eventually break through the cortex, with the central flesh appearing pink due to the release of conidia.
  3. Small, round, slightly depressed spots appear, rapidly expanding to a size of 4-8 mm, or 30-35 mm in other cases. A dark fringe 2 mm wide is outlined along the outline of these spots. The surface has a mat of gray spore layers.

Fruits acquire a bitter taste. They are mummified.


Scab

The pest occurs early on the tree. Scattered small black spots appear on the fruit epidermis with clear boundaries. If the infestation occurs early, apples and pears grow abnormally, and cracks appear on the affected area. If at full ripeness, the spots formed are very small and faintly visible, and the more vivid manifestations are already in storage, and the fruit wilts or is additionally affected by decay.

The causative agent of scab, barn form is Fusicladium dendritic fungus on apples and Fusicladium pirinum on pears.


Grey rot (Botrytis, Botrytis cinerea, grey mold, scorch rot)

Caused by the fungus Botrytis cinerea, it enters the fruit through a lesion on the calyx or pericarp.

It starts as a small, slightly sunken brown spot that grows over the entire surface of the fruit. The affected area becomes enriched and covered with a cottony fungal coat. Damaged apples and pears have a sour taste.

If it rains a lot in summer, apples, and pears infected with lesions rotting directly on the tree.


Blue mold (blue tongue rot, Penicillium rot, blue mold, penicillium)

The causative agent is Penicillium expansum and Penicillium digitatum. spores enter the fruit when the peel is damaged.

The disease starts as small water (rot) spot, gradually grows, not only on the surface but also deep in the flesh, sunken and increasingly wrinkled. If pressed gently, the skin breaks through easily, releasing water.

After the development of the disease, the affected area appears white mycelium, then gray-white spore-like, with many gray-green, green-gray small pieces. Spoiled apples and pears have a musty smell and taste.

Blue mold is able to develop under storage conditions of 28-30°F (-2°C to 0°C), but the higher the temperature, the denser its development.


Olive mold rot disease

The causative agent of this disease is the fungus Alternaria. infests the fruits of the garden through various mechanical damage (insect bites, hail, blows), but the damage manifests itself from the end of the storage period, mainly in overripe apples and pears.

Fruit deterioration begins with dense irregularly shaped spots of dark brown or black, which are eventually covered by an olive-like velvet coating.


Black rot disease

The causal fungus is the fungus Sphaeropsis Malorum Pk. which penetrates apples and pears while they are still in the orchard. It starts with small brown spots that slowly grow and are covered with black, centrally arranged tubercles: pycnidium (plural pycnidia) fungus. The fruit then turns black and becomes mummified.

However, in the case of apples and pears blackened by candida (fruit rot), the fruit skin is smooth and blue, but in the case of black canker, it is simply black and rough due to a large number of conidia.

The main source of black rot infestation of apple and pear fruit is the bark affected by cancer.


Mycorrhizal disease

Infestation occurs through lenticels and skin lesions while the fruit is still on the tree. The causal fungus is the fungus Botrytis cinerea.

The lesions start as dark brown, slightly sunken, rotten spots. As the disease progresses, the affected area is covered with the cottony hyphae of the fungus. The fungus soon spreads to adjacent fruit, resulting in an entire “nest” of rotten apples and pears. Rotten specimens have a sour, musty odor.

Alternatively, only small patches of rot (up to 2 cm in diameter) appear near the calyx.

In the rainy summer years, apples and pears infected with Botrytis cinerea rotted directly on the tree.


Rot fungus (Fusarium)

The causative fungus is the fungus Fusarium avenaceum (Fr.) Sacc. It infects the future harvest during flowering, penetrates into the germinal sac and the disease appears when the fruit is ripe.

The lesions develop first on the inner side of the seed chamber of apples and pears (formation of white-pink or dark spore mats), then inside the flesh of the fruit, and only then on the surface of the fruit (formation of white, gray, or yellowish cotton wool, sometimes in small clusters).


Putrefactive fungus

The causal fungus is the fungus Cladosporium herbarium, which infects the fruit while it is still on the tree. On the skin initially appear small brown (usually oval) strongly depressed, sharply circumscribed areas of decay, while soon growing into irregularly shaped spots, partly black in color. In conditions of high humidity, brown spore mats of the fungus proliferate in the affected area.


METHODS TO PREVENT APPLE AND PEAR ROT

  1. using scab-resistant varieties.
  2. observance of agronomic farming techniques, including timely cleaning of mummified fruit, sanitation and thinning of trees, chemical methods of pest and disease control
  3. decontamination of storage facilities and recyclable containers
  4. timely harvesting of fruits.
  5. rejection of fruits with signs of disease.
  6. gentle removal and packing into containers to avoid skin damage.
  7. observing the temperature and humidity conditions of storage.

MAIN RULES OF STORAGE OF APPLES AND PEARS

The storage rooms assigned to apples and pears should be disinfected in advance, no later than 20 days before fruit picking. Disinfection suits different means: sulfur checker (if the store is at a certain distance from the house), bleaching with 15% lime solution with 2% copper sulfate.

Apples and pears are stored at an average temperature of 33-34°F (0.5-1°C) up to 41°F (5°C), with humidity in the range of 80-90%, using ventilation.

However, widespread apple varieties can suffer from flesh browning at temperature regimes below 39°F (4°C). For most winter varieties, the recommended temperature range is 30-35°F (-1 to 2°C) with a relative humidity of 90-95%.

Hanging wet sacks or water bowls can easily raise the humidity in storage.

When harvesting storage crops, carefully inspect each fruit and discard any fruit that shows signs of disease as well as deformities. Place produce in sterilized crates and refrigerate immediately. Apples and pears left at high temperatures for 24 hours will reduce their shelf life by about two weeks!

During storage, apples and many varieties of pears release ethylene, a substance that exacerbates the aging of plant tissue. Therefore, they are stored separately from other stocks like vegetables and grapes.

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