How to Prevent Damping-off in Your Cannabis Cultivation

What is damping-off?

This cryptogamic disease is caused by fungi but these do not necessarily have to be always of the same type; if your plants suffer from damping-off, the causative fungus is Botrytis most of the times, but Pythium and Fusarium are quite common too. Although this is a fungal condition, this disease is rather a combination of several factors:

• The fungus is present in a substrate and unsterilized medium.
• There is excess water in the crop, the substrate is soaked or has been too wet for too long.
• There is excessive humidity in the environment, coupled with a lack of air renewal.

This disease usually attacks at ground level, that is, the part of the stem that is closest to the substrate. Once it begins, damping is usually lethal because, as we have said before, at this stage the plant is very vulnerable, has a very small size and is most likely to die.

What happens when the damping-off occurs?

These are the signs that will reveal that your seedlings are affected by damping. If you detect them, our recommendation is to eliminate the plants that have already been affected, because their chances to survive are very few, and it is better trying to save those that look healthy. Damping-off acts quickly, so it is very likely that by the time you realise that your seedlings have been infected, they are already dead. Sometimes plants can go from looking healthy to being dead in a single day. However, be careful, if you detect it quickly, you can save some of your other seedlings. These are the phases of damping-off:

• A small whitish spot shows on the stem at ground level.
• The stem loses contour and weakens (it seems as if in that area the stem is dehydrated).
• The part of the affected stem becomes thinner and darker, the rotting extends and intensifies and the seedling is weakened by the lack of circulation of fluids.
• The seedling weakens and dies. It is very common to find the fallen seedling, completely horizontal and folded at the affected part of the stem.

How to prevent damping-off?

As we have discussed above, the key to avoiding both fungi, insect pests and other diseases, is to implement prevention measures. In this case, there are a few simple steps you can take to prevent this infection from entering your crop. Pay attention:

• Hygiene: try to keep the growing area scrupulously clean.
• Control the environmental conditions: during germination, the temperature should be between 21 and 30 ºC, while the humidity should be kept at about 70-80%. Proper air circulation and renewal is of the utmost importance too.
• Control substrate moisture: excess moisture is often the main cause of this malady. Check the substrate of your cuttings or seeds daily to see if they have the correct moisture level. Both to germinate seeds and for cuttings to take root, we recommend using Jiffy discs of pressed and dehydrated peat, as they are a sterilized medium that promotes ventilation.
• Sterilise: use sterile mediums and tools to germinate your cannabis seeds or to root your cuttings (Jiffy, rock wool, etc.).
• Aerate: avoid covering the seeds with too much soil during planting.
• In the case of seeds: do not cover the Jiffy with a plastic cover; it is not necessary and in this way you will reduce the possibility of creating excessive humidity and prevent damping-off. 
• In the case of cuttings: it will be necessary to keep the top vent of your greenhouse closed, because it favours rooting. In this case it renews the air daily and controls that there is not excessive humidity in the substrate.
• End of the growing cycle: thoroughly clean the growing area, including all tools and utensils, in order to minimise the risk of infection in your next crop.

How to stop damping-off?

As we mentioned above, there is little you can do for those plants that have already been affected. If you want to take advantage of those that apparently have not been affected, here are some products that can help: 

• Spread Pythium oligandrum grains on the soil, a parasite that feeds on certain fungi. 
• There are biological fungicides on the market with different trade names that can help you suppress the causes of this disease.