There are several reasons why seedlings die before they are ready for transplanting, but one of the most common is a fungal condition called damping off. Once the fungus gains hold, it can quickly wipe out all of your seedlings. The best way to prevent damping off is to avoid the conditions that encourage its growth in the first place: poor air circulation, insufficient light, overly damp soil, and low temperatures. Signs of damping off include slow or spindly growth, white fuzz on seedlings, mushy stems, collapsed stems, wilting leaves, and pale or discolored leaves.