Black Leg

a disease of agricultural plants in which the root collar and the base of the stem turn black and rot. Causative agents are parasitic fungi and bacteria.

Black leg of cabbage, caused by parasitic fungi, mostly infects cabbage, cauliflower, kohlrabi, and radish seedlings. Diseased plants lose turgor, turn yellow, and droop. The disease is ubiquitous. Control measures include replacement and disinfection of soil in garden frames, treatment of seeds, and proper care of plants.

Black leg of potato, caused by soil bacteria, results in yellowing, curling, and wilting of leaves and in blackening and rotting of the base of the stem. If infected before flowering, the plants form no tubers. With later infection, the tubers are also affected. Control measures include removal of diseased plants, planting of healthy tubers, and disinfection of seed tubers.

Black leg also affects carrots, forage legumes, and seedlings of fruit trees.