Damping off is a disease or condition that occurs in horticultural plants. This condition damages or weakens the seedlings during the process of germination. It is caused by different pathogens and is mostly found in wet and cool conditions. Damping-off is caused by several seed-borne and soil-borne fungi including Rhizoctonia solani and Aphanomyces cochlioides. It is also caused by oomycetes and different fungal species which include Pythium, Fusarium, Phytophthora, Botrytis, Cylindrocladium, Diplodia, Phoma, and Alternaria. Damping off caused by these pathogens has a severe impact on the plant species and can cause great loss to economically important food crops.

Here, we will discuss damping off treatments and causes. One can also refer to this page to know about the common damping off symptoms.

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There are mainly two types of damping off processes, i.e., preemergence damping off and post-emergence damping off. It is caused by the fungus Fusarium equiseti which results in a dry, reddish-brown rot on the hypocotyl. This fungus is the main cause behind both pre-and post-emergence damping-off. Thus, damping off is a serious condition caused to the seeds and must be treated well.

Damping Off Symptoms

Some of the common damping off symptoms that occur in various plant species are given below:

Rotting of seeds before the process of germination causing the seedlings to die before emerging is the first symptom of damping off. This process is also regarded as Pre-emergence damping-off.
Rotting of young seedlings around the crown region, resulting in softening of tissue, wilting, and falling over of plants is another common symptom known as Post-emergence damping-off.
In most cases, the seedlings turn to form a dull green colour along with the drooping of cotyledons. This is mainly caused by Pythium spp. which also causes the development of water-soaked lesions on the hypocotyls at the soil line resulting in seedlings wilt and collapse.
The occurrence of depressed tan to reddish-brown dry on elder seedlings is caused by Rhizoctonia solani, thus infecting seeds and affecting germination. These symptoms are similar to those caused by the Pythium species.
The infection caused by Acremonium spp. tends to develop symptoms usually between 7–10 days after seedling emergence. The infection can be found around the seed coat rand hypocotyl, which turns into a light yellow-brown colour. It develops into a dry red-brown rot within two to three days leading to seedling death.
Development of grey to reddish lesions which later turn coal black in colour. While in wet soil, a frosty coating may cover parts of the black lesion. This symptom is caused by Thielaviopsis basicola.

Damping Off Treatment

Although there is no specific damping off treatment, still use of various precautionary measures can definitely reduce the damping off caused by several pathogens.

We can easily prevent this issue with seedlings by providing good air circulation by use of a small fan. It can also be done by using a cracked lid or germination tray to allow the passing of fresh air. Other steps for preventing damping off include the following:

Use of biological fungicide Mycostop as a seed treatment to prevent seed or soil-borne diseases.
Usage of organic and good quality potting soil
To practise sterilizing your own potting soil in an oven.
To use light and fast-draining seed starter mix.
Planting seedlings in such a manner so that the soil surface is near the top of the container, thus allowing proper air circulation.
Prevent overcrowding of seeds by sowing them in a thin manner. Overcrowding may lead to humid and moist conditions.
Usage of seedling trays that provide water from below. Also, avoid watering the seeds past noon to allow the soil surface and the plants to be dry by evening.
Avoid overwatering of tender seedlings.

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FAQs on Damping Off: Definition, Symptoms & Prevention

1. What exactly is damping-off disease in plants?

Damping-off is a common and destructive soil-borne fungal disease that primarily affects seeds and young seedlings. It is caused by several different pathogens, most notably fungi from the genera Pythium, Rhizoctonia, and Fusarium. These pathogens attack the seedling's stem and roots at or below the soil line, causing it to rot, collapse, and die quickly.

2. What are the key symptoms of damping-off to watch for in seedlings?

The symptoms of damping-off can vary depending on when the infection occurs, but common signs include:

Seedlings failing to emerge from the soil (pre-emergence damping-off).
Young stems appearing thin, water-soaked, and soft or mushy near the soil level.
The stem base (hypocotyl) becoming constricted or shrivelled.
The cotyledons (seed leaves) turning a discoloured grey or brown.
The entire seedling suddenly wilting and collapsing, even when the soil is moist.

3. How do environmental conditions contribute to a damping-off outbreak?

Environmental factors play a crucial role in the development of damping-off. The disease is most severe under conditions of high soil moisture and poor drainage, as waterlogged soil helps the fungal spores to germinate and travel. Cool soil temperatures slow down seedling growth, making them vulnerable to infection for a longer period. Additionally, poor air circulation and high humidity around the seedlings create a perfect microclimate for the pathogen's mycelium to thrive.

4. What is the difference between pre-emergence and post-emergence damping-off?

The main difference lies in the timing of the infection relative to seedling emergence.

Pre-emergence damping-off occurs when the fungus attacks and kills the seed or seedling before it can break through the soil surface. This often results in poor germination rates and patchy seedbeds.
Post-emergence damping-off occurs after the seedling has emerged from the soil. The fungus attacks the stem at the soil line, causing the characteristic symptoms of rotting and collapse.

5. Can a seedling be saved once it is affected by damping-off? Why or why not?

No, a seedling cannot be saved once it shows clear symptoms of damping-off. The pathogens responsible for the disease rapidly destroy the plant's vascular tissues (xylem and phloem) at the stem base. This damage is irreversible and cuts off the transport of water and nutrients from the roots to the rest of the plant, leading to its swift collapse and death. Therefore, the focus must always be on prevention rather than cure.

6. What are the most effective methods to prevent damping-off in a plant nursery?

Effective prevention is key to managing damping-off. Best practices include:

Using sterile potting mix or pasteurising the soil to kill pathogens.
Ensuring pots and trays have excellent drainage holes.
Avoiding overwatering and allowing the soil surface to dry slightly between waterings.
Providing good air circulation by not overcrowding seedlings.
Sowing seeds at the correct depth; planting too deep can promote the disease.
Using fresh, high-quality seeds, or seeds treated with a fungicide.

7. Which fungal species is most commonly responsible for damping-off?

While several fungi can cause damping-off, species of the genus Pythium are the most common culprits. Pythium is a water mould, which is why the disease is so prevalent in overly wet and poorly drained conditions. Other significant pathogens include Rhizoctonia solani, which typically causes stem rot at the soil line in slightly drier and warmer conditions, and species of Fusarium.

8. Are there any biological control methods to manage the pathogens that cause damping-off?

Yes, biological control offers an environmentally friendly alternative to chemical fungicides. This approach involves using beneficial microorganisms to suppress the pathogens. A common biocontrol agent is the fungus Trichoderma, which can parasitize and outcompete harmful fungi like Pythium and Rhizoctonia. Certain beneficial bacteria, such as species of Bacillus and Pseudomonas, can also be introduced into the soil to colonise the root zone and produce compounds that inhibit the growth of damping-off pathogens.