Potatoes turn green and black during storage - why is this happening? Understanding the causes of disease

Potatoes turn green and black during storage - why is this happening? Understanding the causes of disease

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Potatoes are a popular vegetable that can be stored throughout the winter. However, if the storage conditions are violated, you can get your supplies from the cellar and see that they have turned green, stained, or even turned into a slimy gruel.

Both a summer resident who laid potatoes for seeds, and a consumer who wished to have a stock of the product for food, have to deal with different types of spoilage of potatoes.

Why, during storage, potatoes can turn green, turn black from the inside and sprout, and how to store them correctly, is described in our article.

Why are potatoes turning green?

Potatoes are capable of photosynthesis, like all plants. Usually potato tubers are in the ground, in almost complete darkness. However, if exposed to light, the chlorophyll in the skin will react with carbon dioxide and water, causing the potatoes to turn green.

By itself chlorophyll is harmless to health, but the concentration of solanine increases in green tubers. This substance is toxic to humans, so it is dangerous to eat such potatoes. Even the taste will be bitter. It can be used for seedlings, but if the potatoes were stored as a food product, they will have to be thrown away.

To avoid this problem, potatoes need to be stored in a dark place. A cellar, pantry or insulated balcony will do. The main thing is to close it from the penetration of sunlight. Small amounts of potatoes can be kept in the refrigerator, away from the freezer.

Why is it turning black inside?

There are a number of reasons why potatoes can turn black on the inside, from improper fertilization during growing to poor storage conditions. Various diseases can cause blackness, which the plant can infect from the soil or from other plants.

Some potato varieties do not last long in principle. They must be eaten in early autumn. If the potatoes are watered too much, they can darken due to the formation of rot. Perhaps the crop was harvested too early, and the tubers did not have time to form a sufficiently dense crust that could protect against diseases.

If the cultivation and collection of potatoes were carried out according to all the rules, then the happy owner of a large amount of high-quality potatoes should be able to preserve it.

  1. Potatoes need good ventilation and a temperature of +2 ... +6 degrees.
  2. Before storing tubers, it is recommended to remove soil residues from the tubers to reduce the risk of fungal infection.
  3. It is better to fold the crop in boxes with gaps between the boards or boxes with holes.
  4. It is recommended to install them on pallets to improve ventilation.

IMPORTANT! Regardless of whether the potatoes were washed or the soil was simply mechanically shaken off, they must be placed in the storage dry. Sometimes it is recommended to dry it for some time in the sun for additional disinfection with rays.

Germination reasons

The potato tuber is a variant of the nutrient-rich bud. Its purpose is to germinate in the spring and form a new plant. This process starts when it gets warm enough. Sprouted tubers become less nutritious as the starch is consumed for germination.

If the potatoes sprouted during storage, this means that the storage is too warm. Elevated temperatures can also form in the depths of the store if ventilation is inadequate. The sprouts are dangerous to eat and will have to be cut off. The potatoes must be sorted out and placed so that the optimal amount of air is supplied.

So, to prevent sprouting, the room with the potatoes should be well ventilated and cool (but not too cold, otherwise the flesh will begin to darken).


There are over 20 ailments of potatoes caused by fungi and microorganisms. Infection can be transmitted through the soil, with the help of the neighborhood with diseased plants and through the storage, if a crop affected by the disease lay in it a year before. Some common illnesses include:

  • wet bacterial rot;
  • fusarium dry rot;
  • ring rot;
  • scab;
  • darkening of the pulp;
  • glandular spot;
  • hollowness of potatoes.

Let's analyze in detail:

  1. As the name suggests, wet rot caused by bacteria. They enter the potato through damage in the skin, after which wet dark spots form. Gradually, all the pulp turns into an unpleasant slimy mass. The high temperature and humidity in the storage area, combined with the lack of ventilation, contribute to the rapid development of this disease.
  2. Fusarium appears as a result of the spread of fungal spores in storage. They live in the soil and, after a few months, settle in places where potatoes are damaged. Therefore, this disease can often be found in the second half of the shelf life.

    It looks like this:

    • Brown spots appear, then the peel gathers in folds.
    • A cavity is formed inside the tuber, covered with a white fluffy layer: mycelium.
    • Finally, it shrinks.
  3. Ring rot can be detected when cutting the tuber: yellowing and softening of the tissues in the shape of a ring will be visible inside. Subsequently, the site of infection may turn brown and harden with the formation of voids. The disease is not transmitted through soil. The infection develops slowly and is transmitted through the germinated plant to the tubers of the next harvest.
  4. Scab is caused by a fungus and spreads in the ground. It looks like a rash on the skin in the form of black spots or warts. For humans, infected potatoes are harmless, but less nutritious: the level of starch in it is significantly reduced.

    The cause of the growth of the fungus can be:

    • improper fertilization;
    • heat;
    • waterlogging.
  5. Darkening of the pulp in itself is not a dangerous disease. It can occur due to the wrong combination of nutrients in the soil: an excess of nitrogen or a lack of potassium. In addition, the flesh may darken due to frost.

    To prevent this, it is necessary to harvest the crop on time and maintain the optimum temperature in the cellar, above 0 degrees. This is important because it is easier for different types of rot to settle on darkened tubers weakened by frost.

  6. Glandular spot or rustiness looks like rusty spots in the pulp that are visible when cut. This disease is not contagious, it is also not transmitted to the future harvest.

    It arises due to:

    • improper soil composition, in particular, an excess of iron and aluminum;
    • insufficient amount of phosphorus;
    • dryness and heat also contribute to the development of glandular spotting.

    Its appearance can be prevented only during plant growth with the help of proper soil fertilization and sufficient watering.

  7. Hollowness of potatoes - these are voids that can appear inside large potatoes. It is safe to eat such a product, it is also impossible to get infected with this disease. Cavities arise due to the fact that the outer tissues grow faster than the inner ones, and gaps arise between them.

    Such potatoes are stored worse, and it is easier for pathogenic bacteria to settle in it. Therefore, it is important to monitor the composition of the soil and fertilizers when growing the plant in order to prevent hollowness.

Tips on how to store it correctly

  1. Prepare storage containers to allow good ventilation for the crop.
  2. Find a dark room in which you can provide the optimal temperature (we wrote about where to store potatoes here, and what temperature is needed for this is described here.
  3. Carefully sort the potatoes and discard damaged and rotten tubers.
  4. Some gardeners recommend treating the storage with copper sulfate or other substances to fight bacteria and fungi.
  5. You can bathe the tubers in a weak solution of potassium permanganate or brilliant green for disinfection.
  6. Remove soil from potatoes and dry.

If the potatoes were grown correctly, then careful preparation and adherence to all storage conditions will allow them to lie all winter.

Watch the video: Potato problems (May 2022).