Treatments with the fungicides against Alternaria porri mycelia growth were arranged according to their effectiveness in the following descending order, Ridomil gold plus 71.5 % WP, Galben copper 69.8% WP, Ridomil gold MZ-68% WG, Dithane M 45% WP and Kocide 2000 53.8% DF. The mixtures of fungicides were more efficiency than any single fungicide against mycelia growth of A. porri. The candidate essential oils were arranged according to their reduction percentages in mycelial growth at all tested concentrations in the following descending order, clove, cinnamon, thyme, camphor and nigella. Camphor and thyme oils have approximately the same inhibitory activity at all tested concentrations. The current study of greenhouse experiment indicated that the essential oils; camphor and thyme gave low efficiency against onion Purple blotch, while cinnamon and clove oils had approximately the same controlling effect. Generally, efficiency of Ridomil gold plus against onion Purple blotch was more than the essential oils. Mostly, efficiency results of essential oils against Purple blotch in the field through the two agricultural seasons 2017/18 and 2018/19 were compatible with those obtained in the greenhouse experiments. There are no significant differences in disease severity between the treatments of the essential oils, thyme, cinnamon and clove. Data in both seasons confirmed that camphor oil was the least efficient material. All treatments significantly increased the onion yield comparing with the untreated control. The high efficiency of Ridomil gold plus against purple blotch caused a high increase in onion yield. Meanwhile, the tested essential oils were moderately efficient and resulted in significant increase in onion yield.