Peronosporosis (downy mildew) onions: photo, what to do, treatment with fungicides

Onion peronosporosis is a dangerous infectious disease caused by a fungus. Attacks onions and other plants. The main symptom is the appearance of a grayish-purple coating on the feathers. The main treatment measures are treatment with fungicides and folk remedies. For prevention, it is necessary to observe crop rotation, as well as process planting material.

Causes of defeat

Downy mildew (also known as downy mildew) is an infectious disease caused by the microscopic fungus Peronospora destructor. It infects onions and other plants with spores and conidia, which enter the tissues and multiply in them.

Main methods of distribution:

• through the mycelium in the seeds and in the infected bulb;
• through plant debris containing conidia and spores;
• with the help of wild onion roots.

The causative agent is ubiquitous, its spread is provoked by weather factors:

• dew, rain, high humidity;
• moderate temperature, optimal for a pest 10-12 degrees;
• cloudy weather (under the influence of sunlight, fungi die within two hours).

Excessive watering and planting in the wrong place can provoke the development of onion peronosporosis. Therefore, it is quite realistic to prevent the occurrence of the disease, observing the basic rules of agricultural technology.

Description of onion peronosporosis with photo

The infection develops quite quickly, with weak plants dying as early as 14 days after infection. The first signs of onion damage by penosporosis can be seen after three days:

• plaque on individual feathers of a grayish or purple hue;
• sites of infection eventually begin to turn yellow;
• onion leaves are twisted, rot and dry out.

Characteristic signs of the disease appear a month after planting.

If the bulbs were initially infected, symptoms will come on immediately. Plants will look lethargic and lose their normal growth rate. Because the infection spreads quickly, treatment should begin immediately.

How to get rid of peronosporosis on onions

For the treatment of peronosporosis, fungicides are used – chemical and biological preparations. They are the ones that show the most efficiency. At the same time, it is not worth carrying out multiple treatments – some of the fungicides are toxic. If the disease has not yet progressed, and only a few onion plants have been affected, it is recommended to carry out 2-3 treatments with folk remedies, and then monitor the development of the situation.

Fungitsidы

Fungicides destroy the pest in just a few hours. As a rule, 1-2 treatments are sufficient. But it is important to remember the waiting time – the time from the last spraying to harvest. As a rule, it is 1-2 weeks. When using some fungcides (Polycarbacin, Bordeaux mixture, HOM), green feathers should not be eaten.

The main drugs for the treatment of peronosporosis:

1. Revus is an effective chemical fungicide that can be used for processing even in rainy weather. The consumption rate of the initial solution is 600 ml per hectare.

   

2. “Pergado M” – a copper-based agent, is consumed in the amount of 4-5 kg ​​of powder per hectare.

   

3. “Polycarbacin” is another broad-spectrum copper-containing drug. Destroys pathogens of peronosporosis, moniliosis, coccomycosis and other diseases.

   

4. “Bravo” – gives a good and fast result. Refers to organochlorine pesticides, toxic to humans (hazard class 2), therefore, during processing, safety measures must be observed. The consumption rate is 3 liters of the initial solution per hectare.

   

5. “Kvadris” is a fungicide against peronosporosis from the class of strobilurins. It is also quite dangerous (class 2), but it helps to effectively and quickly destroy the pest.

   

Spraying should be total to avoid the spread of infection.

Folk remedies

Folk remedies are safer in terms of toxicity, but the effect of their use is not so strong. They are used in the early stages of the development of peronosporosis, as well as as a preventive measure. Basic recipes:

1. Pollination of plantings with wood ash – consumption of 50 g per square meter. It is necessary to powder not only the plants themselves, but also the surface of the soil. After that, you can water a little so that the ashes are not blown away by the wind.
2. Sour milk whey (from kefir, cottage cheese or other fermented milk products). It is diluted with water in a ratio of 1:10 and used to process onions.
3. You can try treatment with a solution of soda (80 g per 10 liters of boiled water). There also add 2 ml of liquid soap or 2 tbsp. l. laundry soap shavings. Mix until completely dissolved and proceed to spraying. During the season, four such treatments are carried out with an interval of 1 week.
4. If there is onion peel, an aqueous infusion can be prepared from it (500 g per 10 l). The mixture is boiled over low heat for 20 minutes and insisted for several days, after which it is filtered and proceed to the processing of onions from peronosporosis.

Spraying is preferably carried out in the late evening, the weather should be without rain and strong wind

Agricultural practices

To combat and prevent the development of onion peronosporosis, agricultural practices are also used, for example:

1. After harvesting in late summer or autumn, all residues are removed. They must be taken away from the site, thrown away or burned.
2. If the feathers are already severely affected, it is best to dig up the plant and destroy it. Otherwise, it will infect neighboring ones.
3. If onions or other plants were previously affected by peronosporosis in the garden, disinfection or a complete replacement of the soil may be necessary. For processing use the same fungicides or antiseptics, for example, a solution of potassium permanganate 1%.
4. When growing onions, it is important to observe crop rotation. On the same site, landing is carried out no more than four years in a row. It is recommended to plant a crop only after carrots, cucumbers, beets, tomatoes, strawberries. Bad predecessors are other onion varieties, dill, cabbage, parsley, radish, all legumes.
5. Planting onions should not be thickened. The minimum interval should be 20 cm. Planting other plants (parsley, dill) in between is also not recommended.
6. If signs of peronosporosis have already appeared on the onion, it is necessary to completely exclude nitrogen fertilization, mullein fertilizer, and watering. At the same time, it is worth giving potassium and phosphorus regularly, as they strengthen the plant’s immunity.
7. After germination, carry out 1-2 preventive treatments using folk remedies or fungicides.

disease prevention

Peronosporosis is a rather dangerous disease that can lead to significant crop loss. Therefore, it is important to know not only about methods of treatment, but also about preventive measures. The main ones include:

1. Acquisition of healthy planting material – it should be bought in large stores and from trusted suppliers.
2. Cultivation of varieties and hybrids of onions that have a comparative resistance to downy mildew: Stuttgarten Riesen, Antey, Kachinsky, Ellan, Kasatik, Stimulus, Odinovets and others.
3. Bulbs and onion seeds are not only soaked before planting, but also treated in a fungicide solution, following the instructions. At the same time, you can use a solution of “Epin” or another growth stimulator.
4. If planting material is collected from a field where cases of downy mildew have previously been observed, it is important to warm it up at a temperature of 40-42 degrees for 8-10 hours.
5. After each harvest in the fall, a deep plowing of the site is carried out. In the future, it is used to grow onions or other crops (after 3-4 years).

Stuttgarten Riesen – one of the varieties resistant to downy mildew

Conclusion

Onion peronosporosis is dangerous because it spreads rapidly and affects a significant part of the plantings in just 1-2 weeks. Therefore, when growing, it is very important to observe crop rotation, to purchase planting material from trusted sellers. If signs of the disease appear, effective treatment is possible. For this, chemical and biological preparations are used.