During the 2000 and 2001 planting seasons, a disease outbreak in onion (Allium cepa) occurred in Nueva Ecija and other onion growing provinces in Luzon [Philippines]. Symptoms include sunken necrotic spots with clusters of orange to black masses of conidia arranged in subcircular form. Leaves were twisted and curled with dieback symptoms. Bulbs of affected plants were generally slender with elongated necks, roots were short and sparse which led to collapse of the plants. Isolation and test for pathogenicity following Koch's postulates, showed that the disease was caused by Colletotrichum gloesporioides. Captan, Benomyl and Mancozeb reduced disease incidence and apparent infection rate in onion.