Damping-off is a common problem in wet soil with a high nitrogen level. Wet, rich soil promotes damping-off in two ways: the fungi are more active under these conditions, and the seedlings are more succulent and susceptible to attack. Damping-off is often a problem with crops that are planted too early in the spring, before the soil has had a chance to dry and warm sufficiently for quick seed germination. Damping-off can also be a problem when the weather remains cloudy and wet while seeds are germinating, or if seedlings are too heavily shaded.
To prevent damping-off, take these precautions:
1. Allow the surface of the soil to dry slightly between waterings.
2. Do not start seeds in soil that has a high nitrogen level. Add nitrogen fertilizers after the seedlings have produced their first true leaves.
3. Plant seeds after the soil has reached at least 70°F or start seeds indoors in sterilized potting mix.
4. Protect seeds during germination by coating them with a fungicide containing captan or thiram. Add a pinch of fungicide to a packet of seeds and shake well to coat the seeds with the fungicide. For more information on starting seeds, see Starting Seeds Indoors, Starting Seeds Outdoors.
Plant Care for Tomatoes