Damping-Off

Present in almost all soils, the various organisms referred to as damping-off fungi can kill seedlings sometimes even before they emerge, and rot potato seed pieces. Healthy seedlings resist infection, though, and plants generally become less vulnerable with age. Over-watering and poor air circulation foster the growth of damping-off fungi, and plants are more susceptible to the disease in wet, poorly drained, cold soils with a high nitrogen content.