ABSTRACT
Leaf lesions are long and have a pale yellow, glazed appearance; sporulation on these areas produces a thick grey to purple felt of conidiophores. Under less favorable climatic conditions the lesions are restricted to nonsporulating white spots on the foliage. The main infection source for seed production crops is systemically affected onion bulbs. Initially, small white sunken spots develop on the leaves. These enlarge, become zonate and under moist conditions, turn purple, and are surrounded by a broad chlorotic margin. These are very prominent on the inflorescence stalks. Leaf spots are circular to elongate, at first chlorotic with brown or red borders turning brown with sporulation. Foliar pathogens infect and sporulate on the leaves of onions and are therefore ideally located for subsequent dispersal by rain and wind. In addition to crop rotational practices, other approaches are required including that of disposal of plant debris, where possible, particularly in hot climates, to eliminate bulb-borne fungi.
