Why cucumbers develop root rot: how to treat it

Root rot on cucumbers is caused by a fungus that spreads through soil and seeds. In some cases, bacteria are the causative agent. The problem can be prevented by protecting the plants before planting and taking preventative measures. However, failing to do so can jeopardize the harvest.

Cucumber root rot: causes

The problem arises with sudden climate changes, heavy watering, or frost, but these are just the conditions under which the disease begins to develop. The cause is the fungus Fusarium, which is why the disease is also called fusarium wilt. The roots are attacked by several species of pathogens from the genus Pythium. They attack growing cucumbers, causing rotting and yellowing of the leaves. It reproduces via nematodes, soil, and decaying plants.

Fusarium primarily affects greenhouse plants, most often during fruit formation. The pathogen resides in seeds, plant debris, and soil—which is why it's important to regularly renew and till the soil. The fungus penetrates plants through damaged areas, and the risk of infection increases when the soil is loosened. The first symptoms can be identified by external signs:

• darkening of the fetal stem;
• yellow spots on leaves;
• cracks on the shoot near the ground;
• softening of roots, external signs of decay;
• wilting of ovaries at the last stage of the disease.

To avoid confusing root rot with other diseases, compare photos of the diseases. Conditions are crucial for disease development. Rotting occurs at temperatures outside the plant's comfortable range of 15-25°C. Cold snaps or excessively dry periods must be prolonged to allow the organisms time to develop. Short-term temperature fluctuations are not dangerous unless they are frequent. Sudden climate changes weaken cucumbers' immunity, increasing the risk of infection.

The optimal pH level for the active development of harmful microorganisms is between 5 and 6. Temperatures vary widely, but most pathogens begin to reproduce at 7-22°C. The best environment is moist and musty. If you water the soil generously but don't loosen it, you create the perfect conditions for root rot. Aeration is essential for the root system to breathe and metabolize. Without it, the plant weakens and becomes susceptible to fungi and infections.

Dry root systems and high salt concentrations in the soil can also lead to the development of pathogens. As plant parts die, they become a breeding ground for pests. They first occupy the affected area and then spread to healthy areas. The main causes of root rot are:

• too much watering;
• prolonged cold spell;
• sudden changes in temperature;
• presence of plant residues in the soil;
• cucumber seeds contaminated with pathogens;
• failure to observe crop rotation;
• excessive air humidity;
• high concentration of salts;
• dead parts of the root system.

Treatment methods

The first question that arises when root rot appears on cucumbers is: how to treat it? As with other diseases, there are three methods to combat the problem: chemicals, biological products, and folk remedies. Chemicals should only be used in the early stages, before flowering. Once the fruits begin to form, it's time to switch to safer products to prevent the accumulation of harmful substances in the cucumbers. Of course, chemicals are more effective: they are concentrated and target the problem precisely. But folk remedies can also achieve good results.

The decay process occurs quite quickly; at some stages, it's too late to treat root rot. But in the early stages, when wilting has just begun, it's possible to stop the disease and save the harvest. If you look closely, you can see the beginnings of roots at the bottom of the plant. You need to sprinkle fresh soil over them to encourage their development.

Before this, the stem is cleared of lower leaves and slightly tilted, laying it on the soil. After two weeks, new roots will begin to draw nutrients from the soil, taking over all the work of providing the plant with nutrients. The old part of the root will not interfere if treated with disease-preventing agents.

Chemistry

If the signs are clearly visible, root rot cannot be cured with simple methods; active treatments are needed. For example, Previkur Energy is a two-component fungal control product. It targets the mycelium, inhibiting the proliferation of fungal spores. This product can restore the plant's immune system to a healthy state, allowing it to naturally fight pests. After application, root development improves, and cucumbers become more resistant to diseases. It is used in solution:

• 30 ml of the preparation;
• 20 liters of clean water.

Each square meter requires two liters of liquid. The effectiveness is enhanced by combining the product with contact fungicides. For preventative treatment, plants should be treated immediately after planting the seeds, and then every two weeks. Application method: root watering.

Another effective product is Fundazol. It is quite toxic to humans, so it's important to follow the recommended dosage. While the fungicide is safe for plants, accumulation in fruits can be harmful to humans. Its main advantage is its wide temperature range of action. It can be applied almost any time. Plants readily absorb the product, and it begins working almost immediately with regular watering.

Biopreparations

Substances in this group are safer for humans and act more gently, but are comparable in effectiveness to chemical fungicides. Biofungicides can be used at any stage of growth, even after the fruits have formed. Harmful substances do not accumulate, and ripe cucumbers can be eaten immediately after treatment. These products typically last for 3 to 7 days; they should not be combined with each other or other fungicides, otherwise they will not be effective.

Trichocin, named for its main ingredient, is suitable for use during the growing season and has a slight delayed effect, 3 to 5 days after application. It is sold in small sachets that need to be dissolved in a bucket of water. The resulting solution is then poured onto cucumbers, using approximately 100 ml per plant. Do not use with other products.

Gliokladin is suitable for treatment and prevention. It remains effective for one week after application. It should be applied separately from other substances, otherwise the beneficial effect will be neutralized. This biofungicide improves soil condition, combats pathogens, and is safe for plants and people. It can be applied even in the late stages of disease; it will not harm the fruit. Soil pH should not exceed 7, otherwise the beneficial fungus will not be effective. The product is applied under the roots or watered into plants.

The biofungicide Gamair is effective against most fungi. It is used to disinfect soil in greenhouses and treat root rot and other diseases. It is sold as tablets that need to be dissolved in water: two tablets per bucket. Apply the solution to affected areas of plants by watering the soil around the roots.

Traditional methods

If it's too late to use medications or the root rot has only just begun to spread, you can try folk remedies. To combat the problem, create a solution with the addition of household ingredients. These solutions are quite effective, and the ingredients can be found at home. Here are a few recipes that will help combat the disease:

1. Dissolve 2 tablespoons of baking soda in a bucket of room-temperature water. Water the beds first with warm water to moisten the soil, then apply the resulting solution to the roots.
2. Brilliant green is effective against rot due to its copper content, which prevents the development of fungal infections. Mix the solution with water, drop by drop. For prevention, add 1 drop per bucket; for treatment, add 10. Loosen the soil in your garden and water the cucumbers at the roots.
3. The serum prevents the disease's development due to its acidic composition. It is diluted with water in a ratio of 1:9 and 40 drops of iodine are added. The solution is poured onto the roots and sprayed on the green parts of the plant.

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To slow the progression of the disease, sprinkle the lower part of the plant with wood ash, charcoal, or crushed lime; this will slow the progression of the disease. Alternatively, mix 6 tablespoons of chalk and 2 teaspoons of copper sulfate in a liter of water. Wipe the lower part of the plant and, if possible, some of the roots with the mixture.

Prevention

It's not always possible to cure the disease, so it's important to do everything possible to prevent its causes. This means regularly rotating cucumbers, maintaining crop rotation, removing residue from the previous harvest, digging and cultivating the soil, and maintaining the greenhouse. Following these simple rules will help keep the disease at bay throughout the season.

Seed treatment

The primary cause of root rot is contaminated seeds. Pathogens may be dormant and, once released into the soil, will actively attack the roots. Disinfect the seeds with a solution of potassium permanganate or Fitosporin before planting them in seedlings or a greenhouse. You can also dip them in a growth stimulant: this will help the first shoots appear faster and shorten the entire growth cycle by several days.

Soil

Harmful microorganisms often reside in the soil, from where they migrate to plants. Therefore, soil preparation is a necessary step in growing cucumbers. Practice crop rotation to maintain the soil's properties: cucumbers shouldn't be grown in one spot for too long. For disinfection, use a copper sulfate solution at a ratio of 0.3:10. Apply the solution 7 days before planting. The soil should be replenished every season. Old soil can be left in place, but it must be disinfected and mineralized.

Greenhouse maintenance

Root rot affects crops grown indoors due to the unique microclimate created there. Harmful bacteria can persist not only in the soil but also on the walls of the greenhouse, quickly spreading to plants at the first opportunity. The greenhouse must be cleaned after each season:

• treat all structures inside the building with a solution of copper sulfate;
• treat metal parts with disinfectants or laundry soap;
• clear the soil of previous plants;
• rinse the walls and windows with a disinfectant solution.

Viruses and disease pathogens that affected plants last season may be present in the soil. Treat the soil with a disinfectant, and before planting, add fertilizer to the beds; otherwise, the cucumbers will have nothing to eat.

Plant treatment

Preventative measures can help prevent the disease. Treat your plants in advance to avoid problems. A solution containing an antifungal bio-product or a multi-component solution you can make at home is suitable for this:

• copper sulfate;
• zinc sulfate;
• superphosphate.

You'll need 2 teaspoons of superphosphate and one teaspoon of each of the other ingredients. Dissolve all ingredients in a bucket of warm water and water the bushes at the roots every two weeks, without mixing with other products or fertilizers. Use 5 liters of the resulting solution per square meter of planting.

Planting scheme and care

In addition to crop rotation, it's important to maintain planting density. If plants are too close together, their root systems will touch. Disease pathogens can migrate from plant to plant. The optimal number of plants per square meter is 3-4. Plant them closely together, but leave space between rows. If you notice that the plants are lacking nutrients, it's possible that they're planted too close together. By following basic cucumber care guidelines, you can avoid root rot.

1. Water plants only with warm water.
2. Maintain optimal humidity of 70-80% for cucumbers in the greenhouse.
3. Inspect plants to spot signs of rot early.
4. Immediately remove bushes that are too heavily affected to treat.
5. Monitor the moisture level so that the cucumbers are moist but not too moist.
6. Protect crops from temperature fluctuations.

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Mulching the soil will help maintain an optimal environment during cold weather. This will reduce the need for watering, enrich the soil with nutrients, and retain heat so cucumbers can thrive even in cool weather.

Root rot in cucumbers develops in cold, damp conditions due to a fungus. To prevent the disease, follow all care recommendations. Regularly rotate the planting site and replenish the soil. Maintain the desired climate in the greenhouse. Root rot can be controlled with chemicals, biofungicides, or folk remedies, but all methods are effective only in the initial stages. Action should be taken as soon as you notice yellowing leaves or rotten areas on your plants.