Damping-off is a common plant disease that can affect newly sprouted seeds, seedlings, and cuttings. Since the disease appears very early in your marijuana plant’s life, they won’t be able to recover. Learn what causes damping-off, as well as how to spot it and prevent it from happening to you.
You just got new seeds and are looking forward to starting a new grow. After you put your seed in a cup or Jiffy pellet, you watch excitedly as it comes to life; the seed cracks its shell and is now making its way upward towards the light. You watch as the tiny seedling unfolds its first set of tiny leaves. So far, everything is looking great. A few days later, as you check on your new green friend, you find that it has drooped over. Frantically, you try to revive it, maybe by watering some more or administering some of those “special nutrients” – but no dice. Unexpectedly, your seedling has died and you’re stumped. How could this have happened?
WHAT IS DAMPING-OFF?
Damping-off is a common disease that can affect sprouting seeds, seedlings, or cuttings. It can be caused by several types of fungi, namely Pythium, Botrytis, and Fusarium. Pythium is most common. Although fungus is the main reason for damping-off, the disease is normally the result of several conditional factors.
Sometimes, the fungus can already be present in the growing medium or substrate that you use for germinating. This can happen when your substrate is not sterile.
The second factor can be that the substrate has been wet for too long, most likely from overwatering or due to poor drainage qualities.
Lastly, another factor that can contribute to damping-off is excessive humidity in your growing environment, most-often paired with a lack of adequate air circulation.
Each of these factors by itself or in combination increases the risk for damping-off. Once the conditions for the fungus to grow are optimal, the disease will normally attack your plants at the bottom of the stem, just above the soil line. The fungus will weaken the stem, cut-off the fluid circulation of your seedling, and ultimately kill it.
SIGNS OF DAMPING-OFF
Unfortunately, damping-off can happen very quickly. Many times, a seedling can go from looking healthy to dropping dead in just one single day. When this happens, it is already too late to do anything since the fungus has already infected your plant and there is no method of recovery. However, you can learn to spot the signs of damping-off in order to prevent it from happening again.
Among the signs of damping-off include small white spots at the lowest part of the stem, just above the soil line. In this same area, the stem will look weak and thin, featuring a darker colour. If you spot these signs and the seedling is still upright, it is only a matter of hours until it will tip over.
Tip: Fungus gnats, which are tiny, dark, mosquito-like gnats, often appear when moisture and humidity levels are too high. Do not worry so much about getting rid of the gnats, but see them as a sign that something is off with the moisture content in your growing environment. The gnats will disappear on their own when moisture levels in the soil return to normal.
HOW TO STOP DAMPING-OFF
When a seedling has already toppled-over from damping-off, there is nothing you can do to recover it. The best you can do is quickly remove the affected seedling together with its cup to prevent the spread of disease to other seedlings.
When one seedling has already died from damping-off, chances are that your other seedlings are affected too, even if they’re still standing upright. One emergency measure you can try to stop the fungus from spreading is applying hydrogen peroxide. Sprinkle about 1ml (20 drops) of 3% strength peroxide onto the soil of each of your seedlings. The peroxide will kill the fungus. Obviously, there is no guarantee this will save your seedlings, especially if the disease has already progressed quite far. What’s most important is that you know how to prevent this occurrence from happening in the future.
HOW TO PREVENT DAMPING-OFF:
1. AVOID EXCESS MOISTURE AND HIGH HUMIDITY
Excess moisture from overwatering or high humidity are normally the culprits of damping-off. Check your substrate often to observe if the moisture levels are adequate. Avoid too-frequent watering and make sure that your pots or plastic cups allow for fast and easy drainage. If you use a greenhouse or grow-tent with a cover for cuttings, ensure there is a vent on top that allows for proper ventilation. If there is no vent, remove the cover regularly. Always keep in mind that warm and humid means an increased risk of fungus and damping-off.
2. USE A STERILE MEDIUM FOR GERMINATION
For germinating seeds, only use sterile growing mediums. Jiffy pellets, rockwool, or perlite work best. Do not use soils from questionable sources, do not re-use old potting mixes, and do not grow in dirt.
3. USE CLEAN POTS AND CLEAN GROWING UTENSILS
Use only clean growing pots and utensils. To eliminate any harmful pathogens when you plan to reuse pots, clean the pots and your utensils with water and bleach.
4. DO NOT USE FERTILISERS AND TEAS ON SEEDLINGS & CHECK YOUR PH
Do not give your seedlings nutrients and teas in the first one to two weeks. Nutrients at such an early stage in your plant’s life promote the growth of harmful pathogens and prevent your seedlings from developing healthy roots. Start giving nutrients only once your plants have their first set of real leaves. Even then, start only with a light dose of nutrients. Likewise, make sure that your water has the correct pH level. A pH meter will make this process much more streamlined.
5. DO NOT USE A HUMIDITY DOME FOR GERMINATION
The need to cover seeds during germination is a myth that just won’t die. Do not use humidity domes for germinating seeds; only use them when you start cuttings. In the latter case, make sure to renew the air daily and avoid excess moisture build-up.
Now that you know what causes damping-off, you can proceed with confidence in preventing this occurrence from plaguing your precious plants.