Contents
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 culture 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)
Peronosporosis is a disease caused by the pathogen Peronospora destructor Casp. Fungal spores remain 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. You can recognize the disease by shapeless yellowish, brown, red-brown or purple spots that appear on the leaves, and by a whitish or gray powdery coating on the back of the plates.
Symptoms of downy mildew appear on green onions usually in the spring in conditions of high humidity and sudden changes in temperature. The leaves affected by the disease are deformed, dry out and crack. If left untreated, peronosporosis can lead to the death of entire beds.
Peronosporosis usually begins to develop from the top of the onion
Therapy for downy mildew is carried out with copper preparations. In particular, Oksikhom is well suited – 20 g of the product is diluted in a bucket of water and sprayed twice a month. Severely affected plants are previously removed from the site.
Alternaria
Alternariosis, which provokes the fungus Alternaria porri, should be noted among the onion diseases on the feather. The disease usually affects adult 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, crack and wither, the same thing happens with arrows. Sometimes alternariosis affects the bulbs, and then first bright yellow, and then wine-red spots appear on them.
Alternaria 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 humidity – reduce the frequency of watering, organize good drainage in the beds, or transfer the onion 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 beds. At a temperature of 15-20 ° C and with high humidity, the disease spreads very quickly through the plantings. You can recognize it by the numerous reddish-red dots on the leaves of the plant. Gradually, the marks darken and blacken, and the affected plates dry out.
For the first time, rust on the bow appears in late spring.
Rust treatment is carried out using Bordeaux liquid or copper oxychloride. Among the good remedies for onion disease are the drugs Zineb and Kaptan. Spraying is performed at least twice with an interval of a week; it is impossible to cut feathers for food purposes during this period.
Fungal diseases of onion bulbs and their treatment
Some fungi infect the stems and leaves of the onion, others develop outside or inside the underground part. The latter are of particular danger, since such diseases are difficult to notice in time and immediately begin treatment. Only with regular inspection of the beds, it is possible to identify alarming symptoms in the early stages of the development of fungi.
Aspergillosis
Aspergillosis, black mold or black moldy rot, is a dangerous disease caused by the fungus Aspergillus. The disease is difficult to recognize and treat, since in the early stages its only symptom is discoloration of the neck of the bulb. The main signs appear already after harvesting – under the husk and between the juicy scales, a black powdery coating appears, which is a spore mass.
In aspergillosis, the bulbs become watery or dry out completely.
Aspergillosis thrives in warm, high humidity, poorly ventilated storage areas. Bulbs affected by the disease cannot be treated, they can only be disposed of. The fight against the fungus is mainly preventive. Planting material is thoroughly disinfected before being transferred to the garden, and the harvested crop is dried and stored in a cool and dry place with good ventilation.
Cervical decay
A common onion disease during storage is cervical rot, which develops due to the fault of 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 with a careful examination of the plantings can one notice the yellowing of the necks of the plants. But after harvesting, the bulbs begin to rot quickly, 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.
Neck rot spreads rapidly in high humidity and moderate temperatures. The disease manifests itself most strongly on the collected heads, if they are not fully ripe and 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 released varieties that reach full maturity at the time of harvest;
- protect the bulbs from injury and damage;
- do not apply fertilizers in the later stages of crop development, so as not to slow down maturation;
- dry the bulbs well before storing them.
In the beds, it is necessary to maintain cleanliness and timely remove plant residues.
Fusarium (rot of the bottom)
The disease, provoked by fungi from the genus Fusarium, attacks both underground heads and green onion feathers. The development of the disease often begins with yellowing of the tips of the leaves and leads to their gradual death. Fusarium is also expressed in the appearance of a pinkish coating on the bulbs, in the darkening and decay of the roots. The culture almost stops in development, the heads do not mature in time and remain small.
Treatment of Fusarium is to remove the affected bulbs from the beds. Affected plants must be burned, and the remaining specimens should be sprayed with Quadris or Fundazol preparations. As a preventive measure, it is recommended to treat onions before planting from diseases by soaking 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, penetrating into the bulbs through superficial lesions. 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 can see gray, brown or yellow patches on the scales. As the disease progresses, the heads become hard on the outside and soft on the inside, and begin to exude a characteristic moldy odor.
Green moldy rot develops fastest at 20-25°C in humid conditions.
It is not possible to save an onion already affected by a fungal disease. Therefore, treatment consists in prevention – the heads must, first of all, be protected from injuries and abrasions. After harvesting, the onions are qualitatively dried from moisture and kept in a cool room with good ventilation.
In addition to fungal infections, onions in the garden are harmed by viral diseases. They usually do not respond to treatment. Affected plants are simply removed from the site to prevent further spread of ailments.
Onion mosaic
A viral disease, for which there is no cure, is caused by the causative agent Allium virus I Smith, and the garlic mite most often becomes the carrier of the infection. The disease affects the feathers of the onion and its underground parts. The main symptoms are light yellow spots and light green mosaic stripes on the stems. Feathers with this disease curl around the edges and dry out, the onion stops growing and does not release new leaves.
When affected by a mosaic, the onion brings few seeds or becomes sterile
Most often, mosaic infection appears against the background of late planting or with excessive thickening of the beds. Treatment is carried out by getting rid of the affected specimens. The remaining healthy onions in the garden are treated with insecticides to eliminate the garlic mite, and strengthening phosphorus-potassium supplements are applied.
yellow dwarfism
The disease is caused by the Onion Yellow Dwarf Virus. You can recognize the disease by the yellow stripes on the leaves, sometimes covering the entire plate as a whole. 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 carried by aphids.
Classical treatment for the affected onion is not carried out. Infected specimens are removed from the site and burned to stop the spread of the virus. A good prevention of yellow dwarfism is the cultivation of onions from pure seeds – the disease is not transmitted with them.
preventive measures
Onion diseases often manifest themselves in the later stages – after the harvest, when it makes no sense to carry out treatment. Therefore, the main measure of struggle is high-quality prevention.
Processing the site and onion seeds from diseases
In many cases, fungi and viruses infect onions during the planting stage. The problem may be infected soil or infected seeds. So that later you do not have to look for methods of treatment, before starting to grow a crop, you must:
- dig the selected area, remove all plant debris and spill the soil with a solution of potassium permanganate;
- soak the planting material in a biosolution with fungicidal properties, for example, in the Trichodermin preparation;
- warm the sets or seeds at 40 ° C for 12-24 hours.
To protect the onion from diseases, it is necessary to carefully loosen the beds every autumn. Fungal spores in this case will be closer to the surface and die during severe frosts.
Agricultural practices
It is possible to protect plantings from diseases and avoid complex treatment if the basic rules of agricultural technology are observed. 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 culture is transferred to a new corner of the garden annually, and returned to the old soil no earlier than after 3-4 seasons.
- Choice of location. The plant develops well and rarely requires treatment in lit and well-ventilated beds without stagnant moisture.
- Proper watering. Onions on a feather are moistened up to two times a week, per 1 m2 bring in a bucket of water. If the summer turned out to be rainy, additional watering can be omitted. Onions require frequent moisture only until July. In the second half of summer, the intensity of irrigation is reduced and the culture is allowed to ripen.
When growing onions, it is necessary to provide the plant with regular top dressing. With a lack of nutrients in the culture, immunity decreases, and fungal diseases that require treatment develop more often.
Onions in the garden should not be overfed, since an excess of trace elements in the soil also provokes the activity of microorganisms
Other methods
Treating onions with chemicals for diseases is usually not recommended – this method of treatment makes the crop unfit for consumption. However, to protect the culture 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 contribute to the treatment of diseases in the earliest stages.
A good way to deal with pathogenic microorganisms is the use of green manure. A plot for onions can be sown with mustard. It releases substances with antiseptic properties in the process of growth and prevents the spread of fungi.
Store onions 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 comfortably develop.
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 prophylactically, and the storage conditions of the crop are also carefully observed.
