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How to Prevent and Stop Damping Off in Marijuana Plants

How to Prevent and Treat Damping Off in Marijuana Plants

Fungi are everywhere in the environment and are always looking for homes where they can settle and thrive. For many varieties, the fertile soil that marijuana growers use is perfect. Several kinds of fungi that live in soil cause damping off, a disease that attacks and kills young cannabis plants. Fortunately, an educated grower can protect seedlings and often save some mature plants that have been affected. As with everything, careful preparation and education are keys to success. If you want to avoid losing a crop to damping off, create a healthy environment, be on the lookout for early signs of damage, and take immediate action when you spot the problem.

What is Damping Off?

Damping off is a disease caused when fungi attack and kill plants. It is a common problem among cannabis growers but can affect any crop. Also known as Pythium wilt, the disease is typically caused by Pythium, Botrytis, and Fusarium fungus living in soil or planting mediums.

Why It’s Important to Recognize the Condition Early

It is essential to identify the signs of damping off as soon as possible because it can prevent seedlings from growing and it will also attack cuttings. It kills young plants by causing them to rot at the soil level. They begin to wilt and then topple over. If you are not familiar with the condition, it is easy to mistake it for lack of water. That can lead to overwatering, which makes the situation worse.

Damping off acts very quickly, so it is critical to examine plants daily and spot signs of the disease in its earliest stages. As the condition progresses, it prevents nutrients from moving up into the plants. That causes stems to become soft. Damping-off attacks young plants before mature ones. Seedlings may go from being healthy one day to being wilted the next. As per The Marijuana Times, you cannot help a seedling impacted by damping off, but, if you catch the problem early enough, you can often remove affected plants and save the remaining crop.

When you are eliminating diseased plants, make sure to take out the infected roots. You can help prevent the spread of the condition by adding a millimeter of hydrogen peroxide to the soil with an eyedropper. Sprinkling an eighth of a teaspoon of ground cinnamon on the soil can also help.

Factors That Contribute to Damping Off

All of the molds and fungi that contribute to damping off are found in plant debris and soil. There are several ways they get there.

  • When pots and gardening tools in previous seasons are not cleaned, pathogens may cling to them.
  • Insects like fungus gnats carry in fungi. Spores can also be blown in or be introduced through splashing irrigation water.
  • Pythium fungus can be present on dirty hands, hose ends, and tools that have been in contact with contaminated soil or debris.

Once damping off pathogens are present, they easily travel from plant to plant via irrigation water or the growing medium. Garden soil often contains small numbers of pathogens. They thrive in the warm, damp conditions used to grow seeds.

Damping off pathogens also do very well in cold, wet conditions. As a result, the disease is common in seeds that are planted in outdoor soils that are too cold for ideal germination. The issue can also occur when the weather turns cool and wet after planting since these conditions slow germination and growth.

How to Identify Symptoms of Damping Off


You can be sure you are dealing with a damping off problem when you notice any or all of the following:

  • Seedlings do not emerge from the soil.
  • Seedling stems and cotyledons (first new leaves on seedlings) are soft, mushy, and water-soaked. They might also be gray or brown.
  • Thin, water-soaked stems are weak and become almost threadlike in affected areas.
  • Young leaves begin to wilt and turn brown or gray-green.
  • Roots are stunted, have grayish-brown sunken spots, or are absent. You may see a fluffy, cobweb-like growth on plants, especially in humid conditions.
  • Stems may have small, white spots near ground level.
  • Lesions may appear on the plant’s upper portions.

Careful Preparation Can Protect Cannabis Seedlings

It is much easier to prevent a damping off problem than to correct it. The key is knowledge and careful preparation.

If you are growing from seeds, make sure you know their source. Disease free seeds are more likely to thrive. Buy from a supplier who can guarantee seeds with strong genetics.

It is a good idea to begin seeds and cuttings indoors, even if your crop will grow outdoors. By the time you put them in the ground, they are more durable and have a better chance to survive against pests and damping off.

You need to create a safe growing environment. Soak used pots in a 10% solution of household bleach before using them. Clean all tools and use new potting soil. Avoid used soil, compost, or garden soil that could harbor pathogens.

Plant seeds approximately a quarter of an inch deep because moisture intensifies as the depth increases.

Use a potting soil that provides good drainage and make sure water is between 66-77°F since cold water slows growth. Once seedlings have developed several leaves, it is safe to add a soluble fertilizer at ¼ strength unless potting soil contains a slow-release fertilizer. Make sure seedlings get 14-16 hours of illumination from a grow light. Window light is not enough. Bright light can also inhibit damping off.

You need to control the temperature to give young plants the best chance to thrive. When planting indoors, place a heating pad under trays, and set it to 70-75°F. Make sure that outdoor soil is warm enough before planting. According to The Weed Blog, some cannabis can thrive in temperatures as low as 50°F (10°C), although plants will grow more slowly. At 40° F or below, they can be damaged. It is better to be safe than sorry and plant outside when the weather warms up.

Check pH levels periodically. A pH level measures the acidity or alkalinity of the growing environment. A level of 7 is considered neutral. Your crop should have a pH between 6 and 7 to stay healthy. A certain amount of fluctuation is natural in different environments, so it is wise to learn everything you can about the best pH levels for your needs. Indoor crops have different requirements from outdoor plants. You can use a pH meter or kit to test levels in the water and soil to ensure cannabis can absorb the nutrients it needs.

Preventing Damping Off in Growing Plants

Successfully growing a healthy, bountiful marijuana crop requires careful preventative measures. You need to provide the correct balance of light, moisture, and nutrients.

The growing area must be clean and neat. Ensure that tools are scrupulously washed after each use. Germinate seeds or root cuttings in sterile mediums like Jiffy or rock wool.

Monitor the growing environment’s temperature and make sure humidity stays between 70 – 80%. If you are growing indoors, proper circulation and renewal are also essential. Aerate the soil and ensure you do not cover seeds with too much dirt. Take care that the soil around the plants is not too wet since that can lead to “wet feet,” which will destroy plants. You do not need to water plants unless the soil is dry.

Avoid covering Jiffy with a plastic covering since that could create excess humidity. An environment that is too humid can encourage damping off. Keep a close eye on the substrate moisture levels. Monitor them daily. Professionals recommend using Jiffy discs of dehydrated, pressed peat for cuttings and seedlings. It is sterilized and offers ideal ventilation.

If you plant outdoors in an area with frequent rains, make sure the soil can drain well. That stops water from pooling around roots.

As an extra precaution, you can spray the soil with an anti-fungal treatment of garlic oil, chamomile tea, or copper.

At the end of the growing season, clean all tools and pots, to minimize the risk of infecting a new crop.

Saving Plants Affected by Damping Off

Unfortunately, there is little chance you can save a young plant affected by damping off, but it may be possible to help mature plants and save a crop.

The disease is most common in seedlings that are not strong enough to survive the damage. By the time you notice you have a problem, they are usually already beyond help.

If you notice early signs of damping-off on mature plants, it might be possible to salvage them by removing affected parts and spraying wounds with a hydrogen peroxide solution. When stems have especially severe cankers, try spraying them with copper fungicide or sesame, coriander or clove oil.

Bottom Line

Marijuana plants are susceptible to damage caused by fungi living in the soil. The organisms lead to damping off, a condition that kills young plants from the bottom and causes them to wilt and fall over. You can prevent the problem by creating a healthy growing environment and controlling moisture in the soil. It is not possible to save affected seedlings, but you can preserve your crop by removing dead and dying plants and spraying the ground with fungicides.


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