Kassahun T., Temam Hussien, Sakhuja P.K.
Abstract
In Ethiopia, production of sweet orange (Citrus sinensis) is threatened by the devastating leaf and fruit spot disease caused by Phaeoramularia angolensis. This study was undertaken to evaluate fungicides singly and in combination in controlling the disease and to assess the reaction of five sweet orange cultivars to the disease under field conditions in northwest Ethiopia. Three sprays of benomyl, chlorothalonil, copper hydroxide, benomyl +chlorothalonil and benomyl + copper hydroxide were applied at 15 day interval to sweet orange cultivar, Washington Naval. Among the fungicide treatments, the application of benomyl @ 0.039 % plus chlorothalonil @ 0.09 % proved most effective in controlling the disease on the leaves. Application of benomyl alone @ 0.078% proved next best and was significantly better over mixture of 0.039% benomyl + 0.056% copper hydroxide, chlorothalonil alone (0.18%) and copper hydroxide alone (0.115%). The cultivars, Jaffa and Campbell Valencia, were classified as moderately resistant while the cultivars Washington Naval, Pineapple and Hamlin were classified as moderately susceptible. Moderately resistant cultivars need to be considered for new plantations. This must be augmented with three sprays of a mixture of benomyl and chlorothalonil at 15-day interval before fruit set to effectively manage the disease and avoid development of resistance against the systemic fungicide.
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