The causative agent: the fungus Sclerotinia sclerotiorum (Whetzelinia sclerotiorum).
The disease rapidly spreads and infects healthy plants under optimal conditions, the greenhouse is infected in just a couple of days. This results in great damage and loss of yield. Especially for plants growing in greenhouses. In this case, not only the cucumber, but almost all vegetable crops, as well as wild plants, are affected by this disease.
White rot is a fungal cucumber disease, which is easy to recognize on a white flaky-like plaque on the stems and leaves of the affected plants, which over time dense and blacken. The damaged place of the plant becomes softened and watery, the water exchange inside the plant is broken, due to which the plant fades. In greenhouse this disease is more common than in open field. Fruits of cucumber are especially infected and die.
The first signs of infection are the covering of any part of the plant with a light white patch, which looks like a thin air wool. The infected area gradually increases in size and becomes less elastic, moving more and more into a gelatinous form.
In softened parts of the plant, metabolic processes are violated, part of the stem is found without the necessary liquid and nutrients, which leads to fading, and then to death. At the same time, in the last stages of the disease, the fungal mycelium becomes much denser, compared with the initial stage, and darkens to black color. At this stage, the treatment of the plant is already ineffective.
The main source of spreading and infecting white rot is soil, where the fungal mycelium well winterizes and persists for a long time. The disease may also be transmitted by airborne disputes.
Another reason is wrong care and violation of agrotechnical rules on its landing. The humidity level is higher than the optimal, poor ventilation, low temperatures, excessive sowing of rows - all this becomes a "fertile soil" for the appearance of white rot in the greenhouse. To prevent the disease, it is simply not to create conditions for its development.