Aspergillus crown rot (Aspergillus niger)
The fungus causes both seed and seedling rot and drastically reduces plant stand. In moist soil, seeds may be attacked and killed due to rotting. Seeds removed from soil show black sooty cover. The infected areas of seedlings are covered with black fungal spores. Mature plants are also attacked. Symptoms include permanent wilt of branches, and or wilting of entire plant. The dead and dried branches are easily detached from the collar region. Infected pods reveal patches of black sooty spores. Related species (Aspergillus flavus) causes deterioration of seeds.
It also produces the toxin (aflatoxin) in infected seeds that can cause death or other symptoms of toxicity when eaten by animals or humans.
A. flavus as a mould contaminant and toxin producer is much less serious during growth of the crop than during subsequent storage of kernels. Minimising moisture stress during growth can reduce invasion and toxin production by A. flavus.
- Rapid drying to moisture content of about 10% is the only means of preventing infection by A. flavus.
- Minimise damage to the nuts during harvesting because the fungus can easily enter a broken shell.
- Remove diseased crop debris from the field to reduce source of infection.