Collar rot/ Crown rot

Symptom

The disease attacks peanut plant at three stages of plant growth (1) Pre-emergence (2) At seedling stage (3) Adult plant stage. In a moist soil environment, seed may be attacked and killed leading to a pre-emergence rotting. Pathogen produce black mass of spores and seed become soft and watery. 
The first symptom in emerged seedlings is covered by the sporulating fungus at the soil surface. The entire collar region becomes dark brown and shredded. Seedling infection commonly occurs in the cotyledonary-hypocotyl region shortly after emergence. The infected areas become water soaked and light brown, and are soon covered with black fungal spores.
Lesions develop on the stem just below the soil surface and then spread upward along the branches. Because of the woodiness of mature plants, symptoms are generally not observed  until either the branches wilt permanently, or wilting of the entire plant is apparent. The dead and dried branches are easily detached from the disintegrated collar region. The fungus sporulates on the surface of mature pods resulting in patches of black sooty spores.