Onion Diseases: How to Help a Plant

Despite the current view that it is easy to grow onions, reality shows that this is far from the case. Not only is it demanding on soil composition and moisture conditions, onions have a large number of diseases, which are not always easy to cope with. Onion plants are especially often sick on waterlogged clay soils overfed with nitrogen fertilizers.

Onion diseases

Onions belong to crops, cultivation of which is far from every gardener, and you need to imagine the risk associated with the possibility of planting diseases of both viral and fungal diseases. This applies to onions grown on turnips, as well as to those varieties whose green feather is of nutritional value.

Despite the fact that the nature of the diseases, of which there are several dozen, is different, we can assume that the approaches to their treatment are relatively uniform. So, fungal diseases, which are especially severe in conditions of high humidity, can be cured by a limited number of drugs, if you start doing it on time. Viral diseases, as a rule, are not treated, diseased plants have to be destroyed. However, viral diseases can be prevented by fighting their distributors - a variety of harmful insects.

Powdery mildew

Powdery mildew is a disease characteristic not only for onions, and its symptoms are similar in all cases. They can appear already at the very beginning of spring: for perennial bows soon after the growth of foliage, for planted in the early spring - a little later. Yellowish spots appear on the leaves, soon their color turns to mauve, this phenomenon is accompanied by the formation of an abundant white powdery coating, reminiscent of flour.

This coating, which is especially noticeable in the morning, gradually darkens, becoming brown-pink, the leaves become fragile, dry out, the bulbs stop growing. Especially often, the disease manifests itself in thickened plantings, in rainy weather, with a lack of sunlight.

Usually the source of infection is the seed material, so its disinfection before planting is required. Both seeds and seeds can simply be held in hot water (40–42 ºС) for 6–7 hours, or even better, in a pink solution of potassium permanganate. To increase the guarantee of neutralization after this, some gardeners use treatment with biofungicides (such as Bactofit or Poliram).

In addition to processing planting material, the thorough harvesting of plant debris after digging the onion and the immediate digging of the bed helps to prevent the infection of onions for the next year. Crop rotation is also of great importance: it is better to change the location of the onion bed every year, but if it remained in one place for 2-3 years, then they take a break for the same period. A good preventive measure is the periodic scattering of wood ash on onion beds, and from chemical agents - autumn soil treatment with Horus or Oksikhom preparations.

If the disease manifests itself, it is necessary to drastically reduce the amount of watering and stop nitrogen fertilizing, and treat the onions and the soil around it with solutions of fungicides (for example, Bordeaux liquid or Polycarbacin). Of course, it will not be possible to eat onions after such treatments very soon, and feathers, perhaps, are not worth it at all. However, bulbs can be saved if the treatment is carried out in a timely manner.

Peronosporosis (downy mildew)

Symptoms of peronosporosis are similar to the symptoms of powdery mildew: first, a gray-purple powdery coating forms on the feathers. Subsequently, the leaves are deformed, darken and dry. In this regard, the entire plant weakens, which can lead to death: the bulbs begin to rot. The disease spreads very quickly throughout the garden. It can manifest itself about a month after the start of feather regrowth, the same factors contribute to it as real powdery mildew.

With peronosporosis, everything looks like powdery mildew, and control measures are similar.

Both prevention and treatment of the disease almost do not differ from those in the case of powdery mildew. Peronosporosis in an unreleased stage is well treated with infusions of various weeds (dandelion, nettle, etc.), which are also fertilizers. An effective tool is the drug Ridomil Gold.

Video: the fight against peronosporosis of onions

Gray or cervical rot

Cervical rot rarely manifests itself directly in the garden: this can happen only in the case of prolonged rains that occur after lodging the feather. Usually, signs of the disease become noticeable about a month after the harvest. The bulb at the very neck becomes wet, begins to rot, and rotting quickly captures its entire volume. The husk is covered with gray mold, due to which the lying bulbs are also infected.

Since the causative agent of the disease penetrates the bulbs through mechanical damage, a good preventive measure is the periodic disinfection of a knife that cuts the pen by rinsing with a dark solution of potassium permanganate.

Bulbs that are stored prematurely, as well as those whose neck is especially thick, are most often affected. Therefore, proper drying of the crop is of great importance: it should last at least one and a half weeks at a temperature of about 30 ° C and good ventilation.

Cervical rot begins from the top, but then the entire bulb rots

Of the chemicals, Quadrice is sometimes used, which a week before harvesting, they cultivate the soil on an onion bed. Pre-sowing treatment of the seedlings with fungicides, as well as the thorough cleaning of all weeds and plant residues, are essential.

Gray mold

Gray mold is a fungal disease; the fungus is able to affect the bulbs at any time: this can occur both during growth and in winter, during storage of the crop. Unlike gray rot, this disease does not affect the neck of the bulb, but develops on all its other parts. The sources of infection are the same as in the case of neck rot. The tissues affected by the fungus become flabby, become cloudy, acquire a disgusting smell and yellowish color, are covered with a gray coating. Measures for the prevention of infection are the same as for neck rot.

Fusarium (Fusarium rot of the bottom)

The source of the disease lives in the soil, onion infection occurs during the growing season, it contributes to rainy weather, especially in the late stages of plant development. Rotting begins from the lower parts of the bulb, advancing to the apex, the bulb becomes watery, the roots and leaves die off quickly. A case is possible when the infection occurred, but did not have time to manifest itself during the harvest; then the bulb will decay already during storage, especially at high temperature.

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Fusarious rot begins at the bottom, and then goes higher

Since pests contribute to the infection of Fusarium, weakening the plants, one of the methods of disease prevention is the destruction of pests. In addition, it is important to know that early varieties of onions are least susceptible to Fusarium, especially in the case of early planting of a healthy seed. Thermal neutralization of it before landing is necessary. It is important to observe the correct crop rotation, the absence of waterlogging, as well as the timely digging of the bulbs and their careful preparation for storage, including sorting.

Bacterial Onion Rot

Bacterial rot, like Fusarium, can manifest itself already in the garden, to the very end of onion growth, and maybe only during storage. Even in the garden, onion leaves can be covered with small wetting wounds, but they are difficult to see, so the gardener sends the crop for storage without expecting trouble. The disease can manifest itself only closer to winter, gradually destroying the bulb. Bacterial rot is only noticeable when the bulb is cut: normal scales alternate with softened, translucent. Soon the whole bulb rots, producing an unpleasant odor.

With bacteriosis, the bulb rots from the inside

As a rule, bacterial rot develops in immature and poorly dried onions, the source of infection is uncleaned plant debris on which bacteria can live for several years. Therefore, careful cleaning of the beds after harvesting, as well as observing crop rotation are absolutely necessary. In addition, damage must not be allowed when digging the onion and transporting it.

Onion rust

Rust is a common fungal disease of all onion plants, as well as garlic. This is the real scourge of perennial onions grown on herbs. When infected, convex spots of various shapes of light yellow color form on the leaves, which can change color up to bright orange. These spots (“pads”) are fungal colonies. As a result of its influence, the development of leaves and, subsequently, bulbs stops.

Rust only looks beautiful, but it can ruin the crop.

Rust is extremely contagious, and its pathogen is stable, and if the plant debris is not thoroughly cleaned after the end of the garden season, onion infection can continue on the bed for several years. Contamination is promoted by the saving of space: you must not thicken the landing, no matter how much you want. In general, the measures for the prevention and treatment of the disease are the same as in the case of other fungal diseases.

Onion Mosaic

Mosaic is a dangerous viral disease that cannot be treated. When infected, onion leaves flatten, they form a variety of spots, stripes and strokes, mostly yellow, sometimes whitish. Bulbs lengthen, their ripening stops. In the future, the leaves lie ahead of time, many plants die. The probability of a complete death of the crop is not high, but its quantity and quality is significantly reduced.

Since small insects (ticks, aphids, nematodes) serve as carriers of the virus, infection prevention consists in combating them. In addition, the timely extermination of weed vegetation, moderation in irrigation and top dressing, proper crop rotation and the prevention of excessive thickening are extremely important.

Onion Jaundice

Jaundice is also a viral disease, its treatment is impossible. When the virus attacks, the feathers and arrows of the onion turn yellow, starting from the tips and gradually completely changing color. Leaves become flat, often intertwined. Bulbs stop growing. The carrier of the virus is the cicada, on which, as well as various weeds, it hibernates. Affected onions must be destroyed. Preventive measures are the same as for mosaics.

Curly hair

When they talk about curly onions, an inaccuracy is admitted: there is no illness under this name, but curly (or curly) feathers accompany various, mainly viral, diseases. Most often, feathers become curly when infected with mosaic or jaundice. In addition, the onion stem nematode also suffers from a disease such as dithylenchosis. Nematodes are almost invisible to the naked eye, live in the ground, harm both bulbs and onion foliage. As a result, the bulbs crack, and the feathers, interwoven and curly, eventually wilt and die.

Onion Disease Prevention

Although viral diseases are incurable, they can be prevented by properly observing agricultural technology. Fungal diseases that can be cured, it is better not to be allowed on the garden. And if you do nothing with rainy and cold weather, everything else is in the hands of the gardener. In the prevention of onion plant diseases, each item from the following list is important:

  • compliance with the correct crop rotation (periodically, the onion bed moves to another place, new plantings are organized where onions, garlic, lily plants, beets did not grow);
  • mandatory disinfection of planting material;
  • planting or sowing onions as early as possible, without thickening;
  • selection of the sunny location of the onion beds;
  • preventing waterlogging of the soil;
  • making only the necessary doses of nitrogen fertilizers, without excess;
  • permanent destruction of weeds, accompanied by loosening of the soil;
  • thorough cleaning of plant residues after harvesting and immediate digging of the soil;
  • harvesting onions only in dry weather;
  • thoroughly drying the crop before sending it to storage;
  • gentle transportation of the crop to a storage place well cleaned and sanitized in advance.

With full observance of these measures, the likelihood of onion disease is minimized. If this still happened, it is necessary to find out the cause as soon as possible and, if the disease is treatable, proceed to the processing of plantings, otherwise, to the immediate removal of diseased plants.

Treatment of onion plantings in case of diseases

When signs of fungal diseases appear, excess irrigation and nitrogen feeding are stopped, the beds are sprinkled with wood ash, the soil is well loosened and the weed residues are destroyed, and plant treatment products are chosen. Chemical control agents can be used only in the first half of summer, and if onions are grown on a feather, it is advisable to refrain from them. In any case, before spraying with any drugs, it is worth pulling out infected plants, if there are not many.

In the initial stages of the disease, folk remedies can help. These are infusions and decoctions of various plants (dandelion, celandine, marigolds) or tobacco dust. Planting plants such as marigolds, dill, hyssop, and other odorous herbs greatly reduces the risk of disease and drives pests away. If only a few plants are sick, they should be pulled out, and the pits in their place should be poured with a solution of potassium permanganate or copper sulfate (1%).

Marigolds are not only beautiful flowers, but also reliable crop protectors

If a fungal disease affects a large number of plants, the entire bed is sprayed with copper preparations, for example, copper chloroxide (40 g per bucket of water) twice a week. However, leaves after such treatment should not be eaten for 3-4 weeks. Among other drugs, Aktara, Karate, Fitoverm and others are popular. They allow you to fight insect pests that carry dangerous viruses.

Video: spraying onions from fungal diseases

Problems growing onions

In addition to dangerous diseases, gardeners often encounter onion cultivation and other problems that are not directly related to diseases, but that need to be addressed. Some of them are given in the table.

Table: problems with growing onions and their solution

DescriptionCausesNecessary measures
Onion forms small bulbs, early terminates vegetationMost often - thickened planting, possibly a lack of moistureAt the first signs of stunting, thinning is required, after which watering with the introduction of complex fertilizer
Onion leaves turn yellow quicklyIf not a disease - thickening, weeds, lack of moisture, nitrogen, onion flyIf early ripening occurs, measures are useless. Prevention - the right agricultural technology, the fight against onion flies
The bulb does not ripenExcess Nitrogen FertilizerIn the middle of summer, the application of potash fertilizers (at least 30 g / m2 potassium sulfate) or wood ash
Onion bowImproper storage of sets, late landingArrows immediately nibbling at their origin
The leaves dry and breakIf not a disease, lack of moisture or nutrientsAdequate watering, fertilizing
Onion crackingLack or excess of moistureWhen overdrying the soil - watering, with waterlogging - careful loosening
Onion does not growHyperacidity, shading, excess or lack of nitrogenCorrection is possible only next year, but you can try to feed with urea
Leaves twistLack of moisture, nitrogen, pestsIrrigation, top dressing, watering with salt water (100 g of salt per bucket of water)
The onion driesLack of moisture, improper balance of nutrients, pests, cold snapWatering, top dressing, cultivation, extermination of pests
Leaf whiteningIf not a disease - lack of nitrogen, copper, potassium, acidic soils, violation of moisture conditionsFertilizing, correction of agricultural technology

As you can see, each emerging problem has many causes, they are often intertwined, and it is not always possible to resolve the problem. However, proper agricultural technology almost always allows you to grow a good harvest of healthy onions.

Growing onions rarely goes without problems, because it requires careful adherence to agricultural technology. The slightest violations of it can cause difficulties, including diseases that are not always treatable. However, the prevention of diseases dramatically reduces the risk of their occurrence, and constant monitoring of plant health can save most of the crop in case of sudden infection with fungi or viruses.


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