WHY SEEDLINGS DAMP OFF

Sun (Auckland), Volume III, Issue 840, 7 December 1929, Page 34

WHY SEEDLINGS DAMP OFF

The evil so familiar to gardeners under the name of "damping off,” which affects seedlings grown in close, moist places, is caused by a fungus. The seedling is attacked at a point on the lower part of the stem, where the outer tissue is penetrated, the fungus spreading in the form of very thin threads through the interior of the plant. The diseased seedling eventually turns yellow and falls to the ground, as a result of the shrivelling of the stem where the disease first gained entrance. In a very short time all the seedlings in the immediate neighbourhood of the first victim become infected, these in turn spreading the trouble farther afield, until the whole bed is destroyed. Very often a number of plants are attacked simultaneously and, as the disease spreads round each of these original centres, the seedlings die off In patches which gradually enlarge until they all join up to cover the entire area planted. As the afflicted plants die, the fungi grow over them, drawing nourishment from the dead as well as the living, and send up globe-like spore bodies, which in due time germinate to add to the rapidity with which the disease is spread. Resting spore bodies are also produced, which fall and remain in the soil, often for several months after the plants first attacked have decayed, so that any seedlings grown in the same soil as the infected plants are liable to develop the disease, even though not planted till the following season. The minute spores of this fungus are borne by the lightest aircurrent and occur practically everywhere where seedlings are grown in close, moist, shady conditions. When seeds are sown in the open, with sufficient space left between the seedlings to allow free circulation of air, the disease is unable to develop.