Why is peronoporosis or downy mildew of cucumbers dangerous - symptoms and control measures

How does downy mildew of cucumbers appear, and how to distinguish it from the real one? I tried different methods in the summer, but it was not possible to save the cucumbers. I think maybe I was wrong with the diagnosis and it wasn't false dew? What are the signs of this disease? And advise how to process plants from it.

This disease is dangerous, first of all, by its rate of spread, as well as by the extreme vitality of fungi. If they hit only one cucumber bush, and you don't notice it in time, you will completely lose the crop. Downy mildew of cucumbers most often affects greenhouse plants. It is in greenhouses that ideal conditions for the development of fungus. High humidity, condensation collecting on the walls of the room ... And if the plants are still densely planted and there is poor ventilation in the greenhouse, then this is generally a "resort" for fungi. In the open field, downy mildew crops are sick mainly in the rainy season. In dry weather, fungi have no conditions for development. Of course, if you yourself will not fill them with cold water. How to determine that the cucumber beds are sick and is it possible to save them?

Downy mildew of cucumbers - signs of the disease

The scientific name of the disease is peronosporosis. It is caused by organisms similar to fungi from the Peronospore group. The infection affects the deciduous mass and is very quickly transmitted to neighboring plants by air. Fungi are also developing rapidly. In just a week, peronosporosis can destroy all plantings. In the leaves infected with the fungus, photosynthesis is disrupted, and they die off. Sick bushes either do not form an ovary at all, or the fruits grow small, twisted and tasteless. But that's not all: pathogenic fungi enter the soil as a result of shedding withered leaves. And they can even hibernate, and next year they hit new cultures.

In general, the disease goes through 4 stages:

1. First, light angular spots appear on the surface of the leaves. The diseased leaves are still green, but already shriveled and drooping.
2. The spots quickly turn yellow, grow and become covered with an oily coating.
3. At the third stage, a grayish bloom appears on the back of the leaves. The upper spots turn brown and dry out. The bush lags far behind in development, the defeat goes on to the whips, which crack. The ovary falls off, the fruits are deformed.
4. The last stage begins when the spots grow together and affect the entire leaf plate. As soon as they reach the central vein, the leaf falls off.

Peronosporosis is often confused with powdery mildew. You can distinguish them by the shape of the spots. In false dew, they seem to be geometric, have smooth edges, while in real dew they are vague.

How to treat downy mildew

Treatment of the disease is effective only in the first two stages. If the infection has already entered the third phase, then the fight will be meaningless. At the initial stage of the defeat by peronosporosis, you can still save the cucumbers. To do this, immediately remove the stained leaves by burning them. And spray the bushes with a fungicide. Cabrio Duo, Ridomil work well against downy mildew, Previkur (the concentration of the working solution should be 0.5%).

Do not forget to also process the soil itself in the area where the diseased cucumbers grew. It is advisable to remove the top layer of soil and also shed or spray the soil well with a fungicide.

The best way to deal with peronosporosis is prevention. In the greenhouse, keep an eye on the humidity, ventilate regularly, do not plant plants in cramped conditions. Soak the seeds before sowing in copper sulfate, but not more than 10% concentration. You can also disinfect the soil in the greenhouse with it before planting. When growing outdoors, do not water the cucumbers with cold water. Remove weeds in time and also leave enough space between the plants.

How to deal with downy mildew