Damping Off in Cannabis: Treatment and Prevention
So, you’ve just received a few packs of cannabis seeds. Everything looks great after germination, and the first plants are growing their initial sets of teensy leaves. Then, one morning, you go to check on your plants and see that one of them is drooped over, lifeless in its little pot. What happened?! As you research, remaining weed seeds in hand, the term “damping off” appears. What does that even mean?
What is Damping Off in Cannabis Seedlings?
Damping off (also known as Pythium wilt) is what happens to cannabis plants that have been infected by certain types of fungus. Fungal species such as Fusarium, Pythium, and Botrytis can be present in non-sterile soils and growing mediums. They attack newly sprouted seeds and seedlings, stopping nutrient flow to the upper parts of the plant. This causes the stems to get soft and rot at the soil level. Damping off plants will eventually topple over and die.
Signs of Damping Off in Cannabis
Since damping off starts just under the soil, you have to pay careful attention to catch it before it is too late. Once a plant has been affected, it’s best to remove it as quickly as possible to prevent the disease from spreading to any other plants.
Signs of damping off include:
- Degeneration of the stalk and leaves closer to the base of the plant
- Discoloration of the stalk and lower leaves – usually yellow or brownish in color
- Small white spots on the stem just above the soil line
Damping off can even affect marijuana plants with thick stems. In such cases, you may notice lesions forming between the nodes, which eventually turn into dark, red-brown cankers. After this, the stems will lose their thickness and strength, at some point collapsing entirely. At this point, it’s too late to save the plants. If you’re able to catch the earliest warning signs, you’ll need to take quick action to save the seedlings!
How to Save Cannabis That Has Already Damped Off
If you’ve just noticed signs of damping off starting to show, it’s a race against the clock to save your plants. Honestly, it takes some luck too! When signs of damping off appear in one seedling, the others may also be affected. After removing the sickest seedlings, apply hydrogen peroxide to those that are still standing. You only need about 1ml (20 drops) of 3% peroxide dripped onto the soil. Hopefully, the peroxide will kill the fungus and your plants will survive. However, that’s no guarantee, so pray to the weed gods for mercy!
In the case of mature plants with symptoms of damping off, it’s more likely that you can save them from the fatal fungus. Remove all parts of the plant that are affected and apply 3% peroxide to the open wounds.
The fact of the matter is, it’s incredibly difficult to treat damping off in cannabis, as the condition only becomes obvious once it’s too late to treat your plants. A healthy-looking seedling can fall victim to damping off within a day if it’s secretly infected with the fungus. Prevention is therefore the name of the game when it comes to protecting your plants from this formidable fungus, and we’ve got plenty of tips for you.
How to Prevent Damping Off in Cannabis
Once it’s obvious that your cannabis seedlings are damping off, there’s only so much that you can do. However, you can prevent this major problem before it even presents itself! Check out the following tips on how to avoid your weed damping off before it even starts.
Ensure Proper Drainage
In order to prevent damping off in cannabis grown outdoors, it’s recommended to use light, well-aerated soils. Adding perlite or vermiculite to an outdoor soil mix can help to ensure proper drainage in the event of particularly rainy weather. Light soils also allow for more airflow to minimize over-saturation.
Use Bright Lights
Cannabis damping off indoors can be inhibited by the use of bright lights. Start by planting seedlings only about 1 inch deep into the growing medium. The brighter the lights, the better – we recommend using high-intensity discharge (HID) lights or high-output (HO) fluorescent lights.
Don't Overwater
Overwatering is often the root cause of damping off in cannabis seedlings. This one is easy: just remember that less is more when it comes to water. You should only be watering your plants when the top layer of the soil is dry. Otherwise, the growing medium can become oversaturated with moisture, creating the perfect environment for damping off.
Control Humidity and Temperature
Every aspect of the plant’s growing environment comes into play when preventing damping off, including the management of humidity and temperatures of the grow area. When growing cannabis indoors, it’s best to keep temperatures within the 70-85°F (21-29°C) range. As far as humidity goes, you should go ahead and get a hygrometer for your grow tent, just to keep an eye on things and ensure that the relative humidity remains around 40-50%. Proper ventilation is key to maintaining steady temps and pH!
Keep It Sterile
Keeping a sterile growing environment is an excellent way to prevent the breakout of any pathogens. First off, seeds should only be sprouted in fresh, sterile growing mediums like rockwool, jiffy pellets, or perlite. It’s not recommended to reuse growing mediums of any kind – better to just start a new grow with sterile soil.
However, the soil isn’t all that should be clean! Your growing equipment, including pots and tools, should be washed with bleach and water before reuse in order to kill off anything harmful left behind.
Don’t Rush the Nutrients
Resist the urge to fertilize too early! Your seedlings don’t need any extra nutrients in their first couple of weeks of life. During this stage, the plants need to grow healthy root systems. This growth can be negatively affected by excess nutrients. Wait until your plants have their first set of real leaves before giving them a light dose of nutrients. Pro tip: check your water with a pH meter.
Don’t Cover Seeds and Seedlings
It’s a common misconception that seeds should be covered during germination. This is an absolute myth; seeds and seedlings do not need to be covered with plastic. Doing so creates extra humidity that is simply unnecessary and could cause more harm than good. The only time you should be using a humidity dome is when starting cuttings! Even then, the air needs to be renewed daily to avoid excess moisture.
Use Organic Antifungals
Finally, it’s also possible to prevent your weed seedling from damping off by treating the soil with an antifungal spray before planting the seeds. All you need to do is spray the soil with an antifungal treatment made from chamomile tea, garlic oil, or copper. Let it dry out before moving on. It’s much better for the soil and cannabis plants to use more organic alternatives such as these rather than fungicides, which can be detrimental to beneficial organisms.
Also Important: Quality Seeds for Quality Harvests
The above tips and tricks will keep your cannabis crop safe from damping off from seed to harvest. Of course, to ensure that your seeds themselves are healthy and free of disease, it’s best to buy from trusted seedbanks. Here at Herbies, we pride ourselves in selling seeds that are of the highest quality for growing, giving you the ultimate peace of mind.
Herbies Head Shop expressly refuses to support the use, production, or supply of illegal substances. For more details read our Legal Disclaimer.
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