|source image: plant-disease.ippc.orst.edu|
Blackleg is a bacterial disease that is most destructive under warm, moist condition. Although not apparent at that stage, injury begins shortly after infected seed is planted. In the early stage of infection, the seed-borne bacteria cause the seed to rot. Later, soft, wet-appearing inky-black lesions develop at the base of the stem and spread upward for a distance of 3 or 4 inches above the soil surface. Under conditions of severe infection, emergence is affected and irregular stands may develop. Diseased plants are usually small in size and have an erect rather than spreading habit of growth. Their leaves turn from pale green to yellow in color and then curl upward. Eventually, the entire plant dies. Under favorable conditions for the disease, infection may be severe enough to cause the stem to fall over, wilt, and die. Death often occurs before the tubers have formed, but some small tubers may be produced if infection is less severe. Many of the tubers produced by infected plants will be roten at digging time. Tuber rot may be serious in storage. Yield and quality may be reduced considerably when infection is severe.
How to control blackleg of disease potato?
Control of blackleg is based primarily on the use of disease –free seed. The seed disinfectants used to control common scab are also effective in destroying the blackleg organisms that are present on the surface of the seed. Disinfection of the cutting knives with mercuric chloride or formalin also aids in preventing the spread of infection. If diseased plants are detected in the field, they should be removed and destroyed.