Cucumber ascochyta blight (black rot) in a greenhouse: photo and treatment, drugs, pathogen

Content

1 Causes
2 Signs of ascochytaosis with photos
3 Measures to combat ascochyta blight in cucumber
4 Preventive measures
5 Conclusion

Cucumber ascochyta blight is a dangerous infectious disease caused by microfungi. Spreads through infected seeds. It does not manifest itself for a long time, after which it affects all above-ground parts of the plant - stems, leaves and fruits. The main preventive measure is pre-sowing seed treatment. For treatment, chemical and biological preparations and folk remedies are used.

Causes

Ascochytasis is a common infectious disease that is associated with the development of microfungi Ascochyta cucumis and Didymella bryoniae. It affects not only cucumbers, but also other species of the pumpkin family (Cucurbitaceae), including melon and watermelon. Also called black mycospherella stem rot or canker.

The main cause of ascochyta blight in cucumbers is infection of the seeds. In this case, the fungus does not multiply in the soil. It is noted that crops grown in greenhouses most often suffer from ascochyta blight. In the southern regions, the disease often affects cucumbers in open ground.

Fungi develop at normal or elevated temperatures in the range from 10 to 32 degrees.At the same time, they feel normal both at moderate and at high humidity (up to 100%). Therefore, excessive watering cannot be considered as a provoking factor (unlike other types of rot).

Signs of ascochytaosis with photos

The pathology does not make itself known for a long time - the seedlings look healthy, at this stage signs of ascochyta blight appear extremely rarely. The symptoms then spread throughout the plant, affecting the stems, leaves and fruits.

Stems

The infection of cucumbers with ascochyta blight can be determined by the condition of the stems. At the beginning of the season, round spots appear on them. At first they have a gray-green tint and are watery in appearance. Then they acquire a brown color, dry out and become whitish.

As ascochyta blight develops, the spots on cucumbers grow, capturing the entire stem

The surface cracks and a brownish or milky liquid leaks from the tissues. At the same time, the stems continue to develop, so the plant does not die and even bears fruit. Numerous black dots are visible on the surface - pycnidia (fruiting bodies) of the fungus.

Attention! Signs of ascochyta blight are often visible at the nodes of the stems, as well as on the sections that remain after removing the shoot, leaf blade or fruit.

Leaves

If ascochyta blight appears early enough on the stems, the infection affects cucumber leaves during fruiting. First, large spots are formed along the edges of the leaf blades, reaching 5 cm in diameter. They have fuzzy edges and are pale green or yellowish in color.

Cucumber leaves affected by ascochyta blight can be identified by visual inspection

Over time, the spots increase in size and can cover up to half the surface of the leaf plate.The fabrics acquire a brownish tint, then become light yellow. Pycnidia (black dots) appear. If nothing is done, the leaves quickly wither and die.

Fruit

Signs of ascochyta blight on fruits can be very diverse. In practice, there are three forms of the disease:

First, the base of the fruit suffers first, and then its upper part. In this case, the affected tissues dry out and become as if boiled, but at the same time remain hard. Pycnidia are noticeable on the surface, after which the entire cucumber turns black. Subsequently, it rots or, conversely, becomes mummified.
Secondly, the surface of the greens is covered with small ulcers (up to 5 mm in diameter), they contain pycnidia. The spots are dry, there is no rot in them.
Third - the middle part of the cucumber softens, then a rusty stain appears there. Gradually, ascochyta spreads to the entire fruit, after which it dies.

Measures to combat ascochyta blight in cucumber

To combat ascochyta blight, you can use folk remedies, chemical and biological preparations. As a rule, in the initial stages, you can treat with homemade solutions and infusions prepared yourself. But if the disease is advanced, biological agents will be needed. For prevention, as well as for seed treatment, chemical fungicides are also used.

Chemicals

When ascochyta blight appears, cucumbers are treated with various chemicals. Effective fungicides of systemic and contact action:

"Rovral";
"Topaz";
"Topsin-M";
"Fundazol".

The treatment is carried out using a sprayer, completely wetting the entire above-ground part of the plant. You can also water the soil with the solution and treat the seeds before planting. Processing begins early in the morning or late evening.

Fungicide "Rovral" is used for watering the soil, treating seeds and treating the cucumbers themselves. The concentration of the working solution is 0.1%. To prepare it, measure 1 g of powder per 1 liter of water or 10 g per 10 liters (standard bucket).

Treating cucumbers with “Topaz” against ascochyta blight is most effective at the initial stage of infection. The solution is prepared in a ratio of 2 ml of fungicide per standard bucket. The second spraying is necessary 1-2 weeks after the first. During one season, it is enough to carry out 3-4 treatments.

The “Topsin-M” product gives good results when watering the soil under cucumbers. The solution should not be very concentrated - the dosage is 0.1% or 0.2%. The drug is fast-acting - the effect is noticeable just a day after processing the cucumbers. However, it is worth keeping in mind that it is quite toxic (hazard class two). Therefore, it is necessary to work with the solution wearing gloves and a mask.

"Fundazol" is another suitable fungicide against ascochyta blight. Used for spraying cucumbers. The solution penetrates the cucumber tissue through the surface of the leaves and root system. To prepare the mixture, use 10 g of the drug per standard bucket of water or 1 g per 1 liter. The danger class for humans is second, i.e. the use of personal protective equipment is required.

Powdered fungicides are produced in sachets of 10-15 g

Attention! When treating cucumbers with chemicals, you must wait at least a week, after which you can harvest the fruits.

Biological drugs

During fruiting, cucumbers should be treated with biological preparations. To combat ascochyta blight, Vitaplan and Trichocin SP are most often used.These are effective means that completely destroy fungi that cause cucumber pathology.

"Vitaplan" contains bacteria of the Bacillus subtilis strain in an amount of 10¹⁰ colony forming units (CFU) per 1 g. This is a beneficial microflora that destroys pathogenic fungi that cause ascochyta blight. The drug is used for pre-sowing treatment and spraying of cucumbers during the growth period. The concentration of the solution is 5 g per bucket of water.

"Trichotsin SP" contains a special fungus Trichoderma harzianum in the amount of 10¹⁰ CFU. Designed for watering the soil and processing the green part of cucumbers during fruiting. It is recommended to water the soil a few days before planting the seedlings, then again a week later. The standard dosage is 6 g per bucket of water.

Folk remedies

At the initial stages of ascochyta blight, the above-ground part of cucumbers can be sprayed with homemade solutions prepared independently. To do this, use a mixture of the following components:

laundry soap shavings – 20 g;
milk of any fat content – 1 l;
Pharmaceutical alcohol iodine – 30 drops.

The prepared solution is used to treat cucumbers against ascochyta blight 2-3 times with an interval of 10 days.

You can also use another composition:

boiling water – 2 l;
wood ash – 200 g;
laundry soap shavings – 10 g.

First, the ash is placed in boiling water and infused for two days. Then soap is added, filtered and processed at intervals of one week.

During fruiting, treatment is carried out with folk remedies or biological preparations

Advice! After removing the affected leaves or stems of cucumbers, it is recommended to sprinkle the sections with wood ash or crushed coal.

This is a good way to prevent both ascochyta and other infectious diseases.

Preventive measures

It is quite possible to prevent the development of cucumber disease. To do this, experienced gardeners recommend adhering to the following rules:

The main preventive measure is pre-sowing treatment of cucumber seeds. They can be etched in a 2% solution of potassium permanganate or in a solution of a fungicide (for example, Fitosporin, Tattu, Ordan and others).
Choose for growing hybrids and varieties of cucumbers that have good resistance to various diseases, including ascochyta blight.
Treat with folk remedies or biological preparations during flowering and at the beginning of fruiting.
Inspect cucumbers periodically. When the first signs of ascochyta blight appear, remove affected leaves, stems or fruits. In some cases, the plant needs to be dug up and burned.
Maintain temperature conditions in the greenhouse. Ventilate periodically, especially in hot weather.
Treat the greenhouse with disinfectants in the fall or spring (all surfaces, doors, windows).
After the end of the season, carefully remove foliage and cucumber tops from the greenhouse. They must be burned away from the site.

Conclusion

Ascochyta blight of cucumber occurs quite often, especially if you purchase seeds from little-known suppliers. Containing the development of infection and completely defeating it is quite possible. To do this, you need to treat the seeds and spray the soil with a fungicide before planting the seedlings. It is also recommended to periodically inspect cucumber plantings and spray when the first signs appear.