First record of onion leaf blotch (Mycosphaerella allii-cepae) in Argentina

In 1990, onion leaf blotch was observed for the first time in the Lower Rio Colorado Valley (Province of Buenos Aires), the most important onion-producing region of Argentina. Since then, the disease has been found in other production areas of this country. Infections on shallot have also been recorded. The causal agent, Mycosphaerella allii-cepae , was identified on the basis of symptoms, fungus morphology (as its anamorph Cladosporium allium-cepae ) and successful artificial inoculations on onion plants. Although the disease has been present in all seasons since 1990, epidemics of any importance have not been observed in the main crop of dry onions. This is the first record of onion leaf blotch for Argentina.