Content
Treatment of onion diseases is carried out prophylactically and at the first alarming symptoms. Viral and fungal diseases can quickly destroy plantings.
Fungal diseases of green onions and their treatment
The peculiarity of onions and green onions is that the crop rarely suffers from fungal diseases. The plant contains a large number of phytoncides that disinfect the soil and suppress pathogenic microorganisms. However, some ailments still remain dangerous for onions.
Downy mildew (downy mildew)
Downy mildew is a disease caused by the pathogen Peronospora destructor Casp. Fungal spores persist for a long time in plant debris in the beds and in the bulbs themselves, and in the warm season they begin to actively develop.The disease can be recognized by the shapeless yellowish, brown, red-brown or purple spots that appear on the leaves, and by the whitish or gray powdery coating on the back of the leaves.
Symptoms of downy mildew appear on green onions usually in the spring under conditions of high humidity and sudden temperature changes. Leaves affected by the disease become deformed, dry out and crack. If left untreated, downy mildew can lead to the death of entire beds.
Downy mildew usually begins to develop from the top of the onion
Therapy for downy mildew is carried out with copper preparations. In particular, Oksikhom works well - 20 g of the product is diluted in a bucket of water and sprayed twice a month. Severely damaged plants are first removed from the site.
Alternaria blight
Among the diseases of onions, Alternaria blight, which is caused by the fungus Alternaria porri, should be noted. The disease usually affects mature plants with old leaves; the plates are covered with white spots with a light border. Over time, these marks darken, grow and merge with each other. Green feathers crack, break and dry out, the same thing happens with the arrows. Sometimes Alternaria blight affects the bulbs, and then first bright yellow and then wine-red spots appear on them.
Alternaria blight often occurs on onions already infected with downy mildew.
The disease develops most often in plant debris in damp conditions. To treat the disease, spraying with Bordeaux mixture or copper preparations is carried out.At the same time, they control the humidity - reduce the frequency of watering, organize good drainage in the beds, or move the onions to a drier place.
Rust
Onion rust is caused by the fungus Puccinia porri, which overwinters directly on the plant or in fallen leaves in the garden beds. At temperatures of 15-20 °C and high humidity, the disease spreads very quickly throughout the plantings. You can recognize it by the numerous reddish-red dots on the leaves of the plant. Gradually, the marks darken and turn black, and the affected plates dry out.
Rust on onions first appears in late spring.
Rust is treated with Bordeaux mixture or copper oxychloride. Among the good remedies for onion disease are the drugs Zineb and Captan. Spraying is carried out at least twice at intervals of a week; feathers cannot be cut off for food purposes during this period.
Fungal diseases of onion bulbs and their treatment
Some fungi affect the stems and leaves of onions, others develop outside or inside the underground part. The latter pose a particular danger, since such diseases are difficult to notice in time and begin treatment immediately. Only with regular inspection of the beds can it be possible to identify alarming symptoms in the early stages of fungal development.
Aspergillosis
Aspergillosis, black mold or black mold, is a dangerous disease caused by the fungus Aspergillus. The disease is difficult to recognize and treat, since in the early stages the only symptom is discoloration of the neck of the bulb.The main signs appear after harvesting - a black powdery coating appears under the husk and between the juicy scales, which is a spore mass.
With aspergillosis, the bulbs become watery or dry out completely.
Aspergillosis develops in warm and high humidity conditions, in poorly ventilated storage areas. Bulbs affected by the disease cannot be treated; they can only be disposed of. The fight against fungus is mainly preventive. Before transferring to the garden, planting material is thoroughly disinfected, and the harvested crop is thoroughly dried and stored in a cool and dry place with good ventilation.
Cervical rot
A common disease of onions during storage is neck rot, which develops due to the pathogen Botrytis allii. As with aspergillosis, during cultivation the disease practically does not make itself felt, therefore it is difficult to carry out timely treatment. Only upon careful inspection of the plantings can you notice yellowing of the necks of the plants. But after harvesting, the bulbs begin to quickly rot, their scales become loose, and an unpleasant odor appears. If you cut the diseased head in half, then dark areas will be visible on the neck, at the base and on the sides.
Neck rot enters onions through cracks and other damage
Cervical rot spreads quickly in conditions of high humidity and moderate temperatures. The disease manifests itself most strongly on the collected heads if they are not fully ripe and are stored in a warm, poorly ventilated area.
There is no specific treatment for the disease, but preventive measures help protect against rot. In particular, it is recommended:
- grow zoned varieties that reach full maturity by the time of harvest;
- protect the bulbs from injury and damage;
- do not apply fertilizers at later stages of crop development, so as not to inhibit ripening;
- Dry the bulbs well before storing them.
It is necessary to keep the beds clean and remove plant debris in a timely manner.
Fusarium (bottom rot)
The disease, caused by fungi from the genus Fusarium, attacks both the underground heads and green feathers of onions. The development of the disease often begins with yellowing of the tips of the leaves and leads to their gradual death. Fusarium also manifests itself in the appearance of a pinkish coating on the bulbs, darkening and rotting of the roots. The culture almost stops developing, the heads do not ripen on time and remain small.
Treatment of fusarium involves removing the affected bulbs from the garden bed. Affected plants should be burned, and the remaining specimens should be sprayed with Quadris or Fundazol. As a preventative measure, it is recommended to treat onions before planting against diseases by soaking them in a fungicidal solution.
Fusarium often develops with a lack of potassium and phosphorus in the soil
Green moldy rot
The disease occurs under the influence of fungi of the genus Penicillium, which penetrate the bulbs through surface damage. You can recognize green rot by pale yellow areas and weeping spots on the heads, which quickly become covered with a blue-green spore-bearing coating. If you cut an onion in half, you may see grey, brown or yellow areas on the scales.As the disease progresses, the heads become hard on the outside and soft on the inside, and begin to emit a characteristic moldy smell.
Green mold develops fastest at temperatures of 20-25 ° C in humid conditions
It is not possible to save onions already affected by a fungal disease. Therefore, treatment consists of prevention - the heads must, first of all, be protected from wounds and abrasions. After harvesting, the onions are thoroughly dried from moisture and kept in a cool room with good ventilation.
Onion viral diseases
In addition to fungal infections, viral diseases harm onions in the garden. They usually cannot be treated. Affected plants are simply removed from the site to prevent further spread of the disease.
Mosaic bow
A viral disease, for which there is no treatment, is caused by the pathogen Allium virus I Smith, and the garlic mite most often becomes the carrier of the infection. The disease affects onion feathers and its underground parts. The main symptoms are light yellow spots and light green mosaic stripes on the stems. With this disease, the feathers curl at the edges and dry out, the onion stops growing and does not produce new leaves.
When affected by mosaic disease, onions produce few seeds or become sterile
Most often, mosaic infection appears against the background of late planting or when the beds are overly thickened. Treatment is carried out by getting rid of the affected specimens. The remaining healthy onions in the garden are treated with insecticides to eliminate garlic mites, and strengthening phosphorus-potassium fertilizers are applied.
Yellow dwarfism
The disease is caused by the Onion Yellow Dwarf Virus. You can recognize the disease by yellow stripes on the leaves, sometimes covering the entire leaf. The feathers of green onions, under the influence of the virus, flatten, wrinkle and lie down. The underground parts of the culture retain their density, but become smaller in size.
The yellow dwarf virus is usually transmitted by aphids
There is no classical treatment for damaged onions. Infected specimens are removed from the site and burned to stop the spread of the virus. A good prevention of yellow dwarfism is to grow onions from pure-quality seeds - the disease is not transmitted with them.
Preventive measures
Onion diseases often manifest themselves in late stages - after harvesting, when there is no point in treatment. Therefore, the main control measure becomes high-quality prevention.
Treating the site and onion seeds against diseases
In many cases, fungi and viruses attack onions at the planting stage. The problem may be contaminated soil or contaminated seeds. To avoid having to look for treatment methods later, before starting to grow a crop, you must:
- dig up the selected area, remove all plant debris and spill the soil with a solution of potassium permanganate;
- soak the planting material in a biological solution with fungicidal properties, for example, in the drug Trichodermin;
- warm the sets or seeds at 40 °C for 12-24 hours.
To protect onions from diseases, it is necessary to thoroughly loosen the beds every autumn. In this case, fungal spores will be closer to the surface and die during severe frosts.
Agrotechnical techniques
You can protect your plantings from diseases and avoid complex treatment by following the basic rules of agricultural technology.When growing onions, several points are of particular importance:
- Crop rotation. It is necessary to grow onions in areas where peas, tomatoes, potatoes, pumpkins, beans or early cabbage were previously located. The crop is transferred to a new corner of the garden annually, and returned to the old soil no earlier than after 3-4 seasons.
- Choosing a location. The plant develops well and rarely requires treatment in lighted and well-ventilated beds without stagnant moisture.
- Proper watering. Onions per feather are moistened up to two times a week, per 1 m2 bring a bucket of water. If the summer is rainy, additional watering may not be necessary. Onions require frequent moistening only until July. In the second half of summer, the intensity of watering is reduced and the crop is allowed to ripen.
When growing onions, it is necessary to provide the plant with regular feeding. If there is a lack of nutrients in a crop, the immunity of the crop decreases, and fungal diseases that require treatment develop more often.
Onions in the garden should not be overfed, since an excess of microelements in the soil also provokes the activity of microorganisms
Other methods
It is usually not recommended to treat onions against diseases with chemicals - this method of treatment makes the crop unfit for consumption. However, to protect crops from fungi, you can use some biological products with a natural and safe composition. For example, it is allowed to add Fitosporin to water for irrigation at the rate of 15-30 ml per garden watering can. With regular weekly use, the drug will help prevent the development of fungi in the soil and help treat diseases in the earliest stages.
A good way to combat pathogenic microorganisms is to use green manure. The onion plot can be sown with mustard.During the growth process, it releases substances with antiseptic properties and prevents the spread of fungi.
Onions should be stored in a dark place at a temperature of about 5 °C. In such conditions, the crop is less likely to suffer from diseases, since microorganisms cannot develop comfortably.
Conclusion
Treatment of onion diseases is associated with great difficulties and does not always give results. The fight against fungi and viruses is carried out mainly preventively, and the storage conditions of the crop are also carefully observed.
