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Assessing and Measuring of Citrus gummosis (Phytophthora spp.) in Major Citrus Growing Areas of Ethiopia

Mekonen M, Ayalew A, Weldetsadik K and Seid A

Citrus production in Ethiopia is threatened by a number of biotic and abiotic factors. Among these citrus gummosis is one of the most important biotic constraints in the country. This study was conducted with the objective to measure and estimate the incidence and distribution of citrus gummosis (Phytophthora spp.) in major citrus growing areas of Ethiopia. Surveys were conducted in ten major citrus growing areas of Ethiopia. In each orchard, 30 trees were selected and totally 300 trees were assessed for gummosis incidence. These trees were sampled by making two diagonal transects across the field in the form of an “X”. A tree decline was scored on a 0-4 scale where 0=free of any decline symptom, 4=complete drying of the plant. A tree was defined and recorded as cankered when it had any of the following symptoms: discoloration of the bark surface, discoloration of the underlying tissues, dieback, dried the whole part of the plant and exudation of gum from infected tissues. Results showed that growth and fruit production are greatly reduced on trees infected by this disease. Cracked lesions that exude sap are found on infected scions, which become gradually girdled and killed. This symptom was prevailed in 90% of the surveyed citrus orchards. Gummosis was more frequent on scions (trunk and branch) which had 66.96% infection than rootstocks (33.02%). generally the issue needs more attention in the field management including harvesting method (avoid climbing on the tree rather through ladder), don’t touch the tree with the equipments and hands with mud probabily have an inoculums; when irrigating and weeding and finally use of fungicides when pruning of the diseased branch.