Citrus Production, Constraints and Management Practices in Ethiopia: The Case of Pseudocercospora Leaf and Fruit Spot Disease

Abstract

Citrus is economically important fruit crop in Ethiopia. However, its production is seriously constrained by various diseases including Pseudocercospora leaf and fruit spot. Surveys were conducted between June 2012 and May 2013 in the main citrus production areas of the country to assess the spread of the disease, and to determine its incidence and severity. A total of forty-nine citrus orchards in twenty-eight districts were surveyed. Random sampling techniques were used for data collection. The results showed that the disease had prevailed and widely spread in the districts assessed in the wet humid areas of the south, southwest, northwest, and north central parts, but not in the low altitude drier areas of the central rift valley and the eastern region of the country. Accordingly, 63.3% of the orchards surveyed were infected with the disease. The overall mean incidences of the disease on leaves of sweet orange, mandarin, lemon and lime were 36.2, 21.5, 17.1 and 16.3% while disease severity ratings were 2.6, 2.3, 2.0 and 1.7, respectively. Similarly, the average incidences and severities on fruits were 63.8, 29.4, 18.0 and 16.7%, and 4.0, 3.0, 2.0 and 2.0, in the same order. However, disease incidences in the different orchards ranged from zero to 76.7% on leaves and from zero to 100% on fruits. Disease severity ratings also varied from one to five on both leaves and fruits. In general, citrus orchards in the south and southwest Ethiopia that are known to have high rainfall and humidity conditions were more severely affected by the disease than those in the northwest and north central parts of the country. In these areas, respondents indicated that many farmers completely abandoned their citrus trees due to this disease. The causative agent was also identified to be the fungus Pseudocercospora angolensis based on cultural and morphological characteristics, and pathogenicity tests of representative isolates obtained from infected leaf and fruit samples.

Keywords: Citrus Leaf and fruit spot disease; Pseudocercospora angolensis; Ethiopia