Seeds rot without germinating and if germination occurs, the collar region gets rotten with water-soaked lesions. Damaged plant areas will also show water-soaked lesions. The symptoms vary depending on the affected crop. In onions, seedlings rot at the collar region during the early germination period. The sooty mould grows along the veins of the fleshy bulb tissue. In Peanuts, the fungus causes collar or crown rot, characterized by root curling and deformation of the upper part of the plant. In vines, early symptoms include pinhead drops of reddish sap at the infection site. Post-harvest decay results in discolouration, quality deterioration, and reduction in the commercial value of various crops.
Black mould is a common fungus that appears on a variety of starchy fruits and vegetables. This results in food spoilage and deterioration. The fungus Aspergillus niger is spread by air, soil and water. It is generally a saprophyte, living off dead and decaying matter but can also live on healthy plants. The fungus is a common soil inhabitant in Mediterranean, tropical and sub tropical regions. The optimal growth temperature is 20-40°C with good growth at 37°C. Also, in the process of fruit drying, moisture content decreases and sugar content increases which results in a favourable medium for xerotolerant moulds of the fungus.
Drench soil with Trichoderma (enriched in FYM). Neem cake has anti-fungal properties and can also be used to control the spread of A. niger. Treat seeds with hot water at 60°C for 60 minutes before transplanting them. Onion varieties with red scale leaves due to the presence of Phenolic compounds have anti-fungal properties.
Always consider an integrated approach with preventive measures together with biological treatments, if available. If fungicides are needed, use localized drenching of mancozeb or a combination of Mancozeb and Carbendazine, alternatively Thiram. Other common treatments include Triazole and Echinocandin antifungals.