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How to avoid blackening seedlings: tips for beginners

Alina MilsentLifestyle
Blackening of seedlings. Source: Created with the help of AI

Blackening can appear on seedlings after the first shoots appear. Most often, the disease called "black leg" affects crops growing in common containers – containers or boxes. The disease is most dangerous for cabbage, eggplant, and peppers. Flowers, such as petunias and asters, are also susceptible.

It is important to prevent the disease, not to deal with its consequences. OBOZ.UA tells you how to avoid losing seedlings and what measures will help to avoid blackening.

Symptoms of the disease

It is quite easy to determine that the seedlings are affected by the "black leg": the stem begins to blacken and a characteristic band forms on it.

In more mature seedlings with a thicker stem, dark oblong spots first appear just above the soil border.

The infection quickly spreads to the root collar and roots. The very first sign of the disease is the focal lodging of seedlings, the zone of which is expanding very quickly.

Why does the disease occur

Blackening is usually caused by several pathogenic fungi that live in the soil. Most often, these are the basidiomycete fungi Hypochnus solani. Olpidium brassicae can destroy cabbage seedlings. The "black leg" is also caused by root rot pathogens of plants of the genus Pythium.

Excessive moistening of acidic soil leads to blackening of seedlings. Thickened seedling crops, in which the roots of plants are closely connected, are the first to suffer.

Also, sharp fluctuations in substrate temperature are often the conditions for the development of the "black leg". So do not water the seedlings with cold water. In addition, the temperature of the substrate should not be lower than the air temperature for a long time. That is why experts do not recommend growing seedlings on uninsulated window sills and in air-heated greenhouses with insufficient soil insulation.

How to deal with blackening

Measures should be aimed at cleaning the substrate from pathogenic fungi and creating optimal conditions for seedling development.

To avoid blackening, use sterile substrates for growing seedlings, for example, based on coconut fiber, which in principle does not come into contact with soil microorganisms during the production process.

For small plantings, sterilization can be performed by heating the soil to 120 °C, for example, in an oven, for 20-30 minutes. After the substrate has cooled, it should be inoculated with beneficial microorganisms using special preparations.

You can use formaldehyde to disinfect large volumes of soil. Disinfection should be carried out at a temperature of 8-10 ° C, at least 25-30 days before sowing seeds. Having dug up the soil by 20-30 cm, you should first sprinkle 1.5 kg of lime on the surface, or spill it with a 1:50 formalin solution at the rate of 9-10 liters per 1 square meter of soil.

Experienced gardeners recommend treating the wooden parts of greenhouses and greenhouses, as well as equipment, with a 1:25 formalin solution, a 0.1% potassium hydroxide solution, or other disinfectants.

An important condition for preventing blackening is to maintain optimal temperature and humidity in the room where the seedlings are grown. The soil temperature should not be lower than 12-15 ° C, and the humidity should not exceed 75%. Take care of the presence of drainage in the growing containers, a substrate capable of passing excess water, and periodically ventilate the room.

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