The role of seed‐borne Aspergillus niger in transmission of black mould of onion

The incidence of Aspergillus niger (black mould) was found to be high on seed produced in hot (desert) climates. The fungus was transmitted from contaminated seeds to the cotyledons and first true leaves of seedling onions grown under controlled conditions. Seedlings grown from contaminated seeds had longer roots but shorter shoots than those grown from healthy seeds. Seed treatment with either benomyl plusthiramat the rate of 2.5 + 2.5 g active ingredient/kg seed or in hot water (15 min immersion at 60°C) eliminated the fungus in a naturally infected seed stock, untreated seed of which gave 30% infected seedlings.