Damping-off

Above ground symptoms of root rot include stunting, low vigor, or wilting on a warm day. Foliage of such plants may yellow and fall prematurely starting with the oldest leaves.  The roots of a diseased plant will have some shade of brown or black and evidence of water-soaking.  Healthy roots are fibrous appearing and are usually white or tan in color. These symptoms are easily confused with severe mite, aphid, scale infestations, or root-feeding by nematodes or insect larvae. Environmental factors such as accumulated salts in the soil, insufficient light or nitrogen, potbound roots, cold drafts, etc. can be eliminated only by examination of the roots.