What is ascochyta blight of cucumbers, symptoms and control measures

Ascochyta blight of cucumber is an infection of the crop by a fungus. Microorganisms slow down the growth of plants, but do not completely kill them, continuing to parasitize the weakened bush.

Fighting infection is a troublesome and complex process. The spores are transmitted to the crop by infecting the seeds, and then develop along with the plant. How to defeat ascochyta blight on your site and prevent infection of new shoots? Let's figure out what symptoms characterize ascochyta and how to properly deal with it.

Pathogen development

The cause of ascochyta blight is infection of a cucumber colony by parasitic fungi. Greenhouse and greenhouse crops are more often affected. First of all, the fungus is dangerous for weak plants with weak immunity.Rot affects the plant during the fruiting period, less often - during the formation of the stem.

The fungus loves a humid and warm climate, so it is especially active in greenhouses and greenhouses. Fungal spores demonstrate increased activity in the spring, in conditions of good light, when, due to the lack of heat, the cucumber crop is weakened and unable to fight them. The following phases of disease development are distinguished:

1. The parasite infects cucumber seeds and then waits to develop as the plant grows. The spores are on the seeds in a state of suspended animation. The moment they are planted in the soil, they begin to gradually increase their population along with the plant. The fungus affects the upper tissues of the cucumber, but does not affect the vascular system, so the plant retains the ability to vegetate, although in a weaker form.
2. The fungus enters its active form when leaves are set on the cucumber. The defeat begins from the lower tier of leaves, first the pathogen colonizes the tissues, and then the vessels. By April-May, the mycelium forms and begins to infect neighboring leaves of the plant by air with the help of spores. In this case, the pathogen expands the area of ​​its presence up the stem, already affecting the middle leaves.
3. The fungus penetrates into the fruits and leaves of the upper level by the end of the growing season. Faded watery spots appear on the fruits, which then darken and give way to rust. Weakened fruits degrade and begin to gradually dry out and die.

The fungus does not develop in the soil. During storage, it does not transfer from one fruit to another. It also does not reproduce in the roots.

Important! To slow down the expansion of the fungus, it is recommended to carry out thermotherapy of seeds and disinfection with fungicides, which slows down the development of the disease by 15–25 days.

Symptoms of the disease

If preventive measures fail to stop the expansion of the fungus, the parasite begins to infect the external tissues of the plant. Infection of a cucumber with black stem rot can be determined by the following characteristic signs:

1. First, watery gray spots begin to appear on the stem. Then they begin to turn white and take over an increasing area of ​​the stem. Black rot begins to develop on vulnerable parts of the stem where pinching, leaves and fruits were removed.
2. When infected during fruit growth, the fungus begins to infect the edges of the leaves. Then the surface of the leaf turns brown, and the disease spreads to the fruit.
3. The fruits dry out and visually look withered, remaining hard to the touch. Such a cucumber stops developing, and subsequently decomposition processes begin in it.
4. A form of infection is possible in which the fruits become covered with ulcers or turn white. The body of the fruit is covered with a rusty coating and mucus appears, under the influence of which the cucumber begins to rot.

In its development, the fungus passes along with the plant through all stages of its growing season, gradually rising along the stem from the roots to the upper tier of leaves and fruits. Therefore, if you slow down its progress using a set of preventive measures, you can successfully grow a cucumber crop and even harvest a crop from it that the fungus will not have time to reach.

Important! Removal of the lower leaves must be done after the appearance of mature pycnidia of the fungus in early summer. This allows you to restrain the development of mycelium.

Methods of prevention and elimination

It is difficult to combat the fungus, since it does not respond to fungicides during the growing season. For ascochyta blight on cucumbers, control measures should be as follows:

• water the crop in the evenings with warm water;
• cover the seedlings with film until a pronounced stem with leaves is formed;
• carry out crop rotation so that spores do not infect the cucumber crop every year;
• buy and plant varieties resistant to ascochyta blight;
• add chemicals to the soil to protect the crop from disease;
• remove all affected leaves on the bush.

If the fungus is fixed on the area, it is necessary to treat with the following preparations:

1. Add green manure to the soil shortly before planting seedlings. They increase plant immunity and allow them to more effectively resist fungus. To further enrich the soil, you can also plant sanitary crops such as rye and oats on green manure. Subsequently, such a crop is crushed and plowed with manure into the soil before planting cucumber seedlings.
2. Disinfect the inside of the greenhouse by spraying a formaldehyde solution on the walls and ceiling. Additionally, steam the soil, although this only has a weakening effect on the parasite.
3. Treat seeds with active fungicides such as Vincit, Tiram and Saprol. They will weaken the fungus until it disappears completely.
4. If leaves and fruits are damaged, spray the plants with Bordeaux mixture or a mixture of urea and copper sulfate. In the case of fungus on the stems, a powder consisting of copper and chalk is applied to them.

Using the above methods, you can significantly slow down the progression of ascochyta blight along the stem, and as a result, completely eradicate the disease.