Downy mildew (downy mildew) of onions: control measures, photo, description, video

Content

1 Causes of defeat
2 Description of onion downy mildew with photo
3 How to get rid of downy mildew on onions
4 Disease prevention
5 Conclusion

Onion downy mildew is a dangerous infectious disease caused by a fungus. It affects 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 and also 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 and multiply in tissues.

Main distribution methods:

through the mycelium in the seeds and in the infected bulb;
through plant debris containing conidia and spores;
using the roots of wild onions.

The pathogen is present everywhere, its spread is provoked by weather factors:

dew, rain, high air humidity;
moderate temperature, optimal for the 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 trigger the development of onion downy mildew. Therefore, it is quite possible to prevent the occurrence of the disease by observing the basic rules of agricultural technology.

Description of onion downy mildew with photo

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

plaque on individual feathers of a grayish or purple hue;
sites of infection begin to turn yellow over time;
onion leaves become distorted, rot and dry out.

Characteristic signs of the disease appear a month after planting

If the bulbs were initially infected, symptoms will appear immediately. Plants will appear limp and lose normal growth rates. Since the infection spreads quickly, treatment must begin immediately.

How to get rid of downy mildew on onions

To treat peronosporosis, fungicides – chemical and biological preparations – are used. They are the ones that show the greatest effectiveness. 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 affected a few onion plants, it is recommended to carry out 2-3 treatments with folk remedies, and then monitor the development of the situation.

Fungicides

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 period - the time from the last spraying to harvesting. As a rule, it is 1-2 weeks. When using some fungcides (Polycarbacin, Bordeaux mixture, HOM), green feathers cannot be eaten.

The main drugs for the treatment of peronosporosis:

"Revus" is an effective chemical fungicide that can be used for treatment even in rainy weather. The consumption rate of the initial solution is 600 ml per hectare.
“Pergado M” is a copper-based product, consumed in the amount of 4-5 kg of powder per hectare.
"Polycarbacin" is another copper-containing drug with a broad spectrum of action. Destroys pathogens of peronosporosis, moniliosis, coccomycosis and other diseases.
“Bravo” – gives good and quick results. It is classified as an organochlorine pesticide and is toxic to humans (hazard class 2), so safety precautions must be observed during processing. The consumption rate is 3 liters of initial solution per hectare.
"Quadris" is a fungicide against peronospora from the class of strobilurins. It is also quite dangerous (class 2), but it helps to effectively and quickly destroy the pest.

Important! Fungicides and other treatments for onions against downy mildew are used to treat not only infected but also healthy plants.

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 as strong. They are used in the early stages of the development of peronosporosis, and also as a preventive measure. Basic recipes:

Pollination of plantings with wood ash - consumption 50 g per square meter. You need to powder not only the plants themselves, but also the surface of the soil. After this, you can water it a little so that the ash does not blow away with the wind.
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.
You can try treatment with a soda solution (80 g per 10 liters of boiled water).Add 2 ml of liquid soap or 2 tbsp. l. laundry soap shavings. Mix until completely dissolved and begin spraying. During the season, four such treatments are carried out with an interval of 1 week.
If you have onion peels, you can prepare a water infusion from it (500 g per 10 l). The mixture is boiled over low heat for 20 minutes and left for several days, after which it is filtered and proceeds to treating onions for downy mildew.

It is advisable to spray in the late evening; the weather should be free of rain and strong winds.

Agrotechnical techniques

To combat and prevent the development of downy mildew on onions, agrotechnical methods are also used, for example:

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

Disease prevention

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

Purchasing healthy planting material - it should be purchased in large stores and from trusted suppliers.
Cultivation of onion varieties and hybrids that are comparatively resistant to downy mildew: Stuttgarten Riesen, Antey, Kachinsky, Ellan, Kasatik, Stimul, Odinovets and others.
Before planting, onion bulbs and seeds are not only soaked, 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.
If planting material is collected from a field where cases of peronosporosis have previously been observed, it is important to warm it at a temperature of 40-42 degrees for 8-10 hours.
After each harvest, deep plowing of the area is carried out in the fall. In the future, it is used to grow onions or other crops (after 3-4 years).

Stuttgarten Riesen is one of the varieties resistant to downy mildew

Conclusion

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