Incidence and sites of visible infection of Aspergillus niger on bulbs of two onion (Allium cepa) cultivars

Abstract

The incidence of visible black mould caused by Aspergillus niger on the neck, middle and base of onion bulbs was evaluated in the brown-skinned fresh market cultivar Creamgold, and the white-skinned dehydrating cultivar Southport White Globe. Black mould occurred all over the bulbs, but the incidence was lower in the neck region. Infection levels were consistently higher in Creamgold (77.5%) than in Southport White Globe (46.6%). Infection levels increased with increasing bulb size. Nitrogen topdressing was also evaluated, but in a situation where nitrogen levels were already high. Rates up to 150 kg N/ha had no clear effects on black mould incidence and no significant influence on bulb yield or soluble solids concentration.