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.