Every beginner and experienced gardener must have planted at least a couple of beds of such tasty and healthy vegetables as cucumbers. The vegetable contains many vitamins of groups B and C, as well as a sufficient amount of minerals, such as calcium, phosphorus, potassium, iron and magnesium. Cucumbers are an integral part of our diet in a raw, salted and pickled form. Growing them is simple enough, but you need to be prepared for unpleasant surprises, namely, the plant is prone to such a common disease as perinospora.
What is dangerous and where does it come from
Perinosporosis is a fungal disease that affects the foliage and stems of a plant. Downy mildew can destroy a plant in the shortest possible time or significantly reduce its yield. 
The best environment for malicious spores is moisture, which is why plants start to hurt more often after rain or excessive watering. The air temperature also plays a big role: if at night after the rain the thermometer drops below 9 degrees Celsius, the plants automatically fall into the risk group, as it is in this weather that numerous species of pseudogribs from the Peronosporov family progress.
It is possible to grow cucumbers not only in the open field or greenhouse, but also by more non-standard methods: in buckets, barrels, plastic bottles, on the windowsill, on the balcony or in hydroponics.
Another cause of powdery mildew may be too alkaline soil. Fungal diseases are characterized by increased winter hardiness and are able to maintain their viability in the soil and seeds up to 6 years.
Signs of appearance
You will immediately realize that the plant is sick: yellow or brown spots will appear on the top of the foliage. Soon, the lower part of the leaf is also affected, which is covered with a violet-gray bloom. The disease progresses incredibly fast, the leaves turn yellow and dry out. After 4-5 days from the plant can remain only the stems. Naturally, this contributes to poor ovary or slower growth of the fruit. Cucumbers affected by fungus, lose taste. 
Important! The disease spreads very quickly and can damage other cultures. - this is assisted by pests capable of spreading spores, for example, aphid and whitefly.Most often the disease affects the plants in the phase of formation or ripening of fruits, it all depends on the time of planting. In this case, malicious disputes can safely remain in the ground, and the disease will be excited under comfortable conditions for them. It is believed that the fungus can cause most harm to greenhouse crops.
Prevention
First of all, disease resistant varieties should be preferred. Still need to correctly refers to sowing: seeds before planting must be processed, for example, in a solution of potassium permanganate. It is better to plant early varieties, so as not to give chances of peronosporosis disputes to develop before the harvest ripens. 
Experts do not recommend planting cucumbers every year at the same place - change the location of the beds each season, and this will reduce the risk of infection. At the end of the growing season, you need to cut the stems with leaves and burn. If the culture is grown in greenhouse conditions, then, in addition to the removal of plant residues, it is necessary to remove the top layer of soil and disinfect.
Agrotechnical methods of struggle
First of all, the location of the beds plays a role. It is necessary to avoid too wet areas and the neighborhood with buildings in those places where water may accumulate, or drops may fall from the roof. We must make it a rule to process the seeds before planting. One of the effective methods is the treatment of planting material with hot water (50-55 ° C). 
Seeds are soaked for 10-15 minutes, then you can start planting. You can not overmoisten the plants, watering should be timely, but moderate. One should not neglect regular top dressing of the soil: if cucumbers get enough nutrients, the risk of peronosporosis is significantly reduced. Preventive spraying of young plants with biological preparations, which are widely represented on the market, are welcome.
Important! When greenhouse cultivation of cucumbers, you must constantly keep under control the humidity in the room. As soon as spots appear on the foliage, you should hastily remove it so that there are no petioles.Phased implementation of preventive measures does not guarantee 100%, but significantly reduces the chances of infection with fungal diseases.
Active fight
If it was not possible to prevent the peronospora of cucumbers, proceed immediately to treatment. The method of struggle depends on the neglect of the disease and your preferences. 
In order to defeat the fungus, first of all it is necessary to remove its foci - the parts of the plant that are already damaged, and immediately burn them. After that, you can proceed to therapy.
Chemicals
The most effective chemical agents in the fight against downy mildew are fungicides. These substances are used both to combat fungus, and for seed dressing. At an early stage of plant disease, 0.5% solutions of the Bord Mixture, Ridomil, Kurzat and Oxyhoma are used.
Spray both the affected plant and the soil around it. It is necessary to use such preparations from downy mildew on cucumbers with caution, not forgetting about their high toxicity and the danger of such control measures for people and animals. 
Did you know? Spines on the fruits of cucumber are needed in order to get rid of excess moisture.
Folk remedies
If you prefer safer folk methods of fighting the fungus, then in this case there is an incredible number of different ways. It is believed that ordinary soda is very effective against downy mildew on cucumbers.
For the preparation of therapeutic solution will need 30 g of soda, 5 liters of hot water and 5-10 ml of liquid soap. The ingredients are thoroughly mixed until complete dissolution, then allow the mixture to cool. After that you should spray the soil and plants. In order to defeat the fungus, you will need at least 3 such procedures. Two spraying are carried out in a row, and the third carried out after 7 days to fix the result.
Learn more about pharmacy pest control products.
For processing plants using a mixture of iodine and milk. To do this, 10-12 drops of iodine must be dissolved in one liter of milk (fat does not matter) and diluted with 10 liters of water. Then spray the plants with a spray bottle. Able to defeat harmful fungi and a weak solution of potassium permanganate. 1-2 g of the substance is dissolved in 10 liters of water and sprayed with plants.
You can fight with powdery mealy dew using ash: it is dissolved with boiling water. Take 2 tbsp. substances to 3 liters of water. The resulting mixture will give an infusion, and then filter and spray the plants and the soil.
You can prepare the medicine from onion peel - only, it will be effective only in the early stages of the disease. 350-400 g of husk is poured with 10-12 liters of water, brought to a boil and left for 2-3 days. The present filtered solution is used for spraying cucumbers. 
An accessible and infinitely useful fertilizer - manure, will also help to defeat a fungal infection. To prepare the mixture, take 3 parts of water and 1 part of manure, stir and leave for 4-5 days. Then filter the prepared solution, dilute with water and process cucumbers. This method not only helps to defeat the disease, but also feeds the plant, adding vitality to it.
Find out why cucumber ovaries turn yellow, how to deal with powdery mildew and fusarium wilt, and how to treat plants from diseases and pests.
Resistant varieties
Due to the continuous selection of vegetable crops cultivated cucumber varieties resistant to downy mildew. Naturally, no one says that by planting these varieties, you will never see signs of peronosporosis on your plants, but the risk of infection is significantly reduced.
Preference should be given to the following cucumbers:
- "Darling" - resistant to peronosporoza, variety has a good yield, as well as excellent taste. Fruits ripen approximately 55 days after emergence.
- "Tom Thumb" - the crop ripens on the 40th day after germination, that is, very quickly. The variety is resistant to pests and diseases.
- "Spring" - A variety that is distinguished by its highest yield and unpretentiousness, is also valued for its taste. The fruits ripen on the 50th day after germination.
Did you know? There is a celebration dedicated to this vegetable. - July 27 is International Cucumber Day.
In order to protect your crop from a fungal infection, you must follow the rules of agricultural technology and, of course, always be in the attention and fully armed. If the first signs of peronosporosis suddenly appear, we must begin to act with lightning speed, and we have figured out what exactly to do.
