Abstract
Forest plantations in Ethiopia are mainly exotic genera of Eucalyptus, Cupressus, Casuarina, Pinus and native Juniperus species. Plantations species have suffered at varying degrees of attack by disease causing agents, particularly Amhara region is among regions with plantation forests that have in recent years been subjected to attack by diseases in Ethiopia. Plantation trees in commercial stands, farmlands and woodlots were surveyed for diseases symptoms in 20 selected areas of Amhara and Tigray from May to June 2016.Leaf blight, leaf spot, tip blight and stem canker were the most common symptoms appeared during the survey period with leaf spot and stem canker the most prevalent. Tree samples showing clear disease symptoms were collected, surface sterilized, cultured and morphologically characterized for pathogen identification. A total of 42 isolates of fungi colonies were identified from samples collected of 20 localities. Morphological characterization of fungal isolates reveals, six fungal genera belonging to Alternaria, Dioplodia, Pestalotiopsis, Curvularia, Phoma, and Penicillium were the cause of the symptoms of the symptoms of the observed disease. Among the isolates 14 (33.3%) were Alternaria species, 15(37.7%) were Phoma species, and the remaining 13 isolates were Diplodia3(7.2%), Pestalopsis7(16.7%), Curvularia2(4.7%) and Penicillium1 (2. 4%).Based on the findings of the study Phoma lingam, Phoma glomerata, Alternaria alternata, genera of Curvularia, Pestalotiopsis, Penicillium, and Diplodia were found to be the cause of diseases of the tree plantations. Phoma and Alternaria species were the most prevalent isolates, showing a majority of symptoms observed on plantations were due to their co-infection. The pathogenicity test result of the research also confirms fungal isolates were the cause of the symptoms of the disease observed. The findings of this research enable to study and design appropriate management options for the future prevention and control of the diseases especially when there is prolonged environmental stress in the country.
Highlights
Plantation forests are cultivated forest ecosystems established by planting or seeding using introduced or indigenous species in the process of afforestation and reforestation, primarily for wood biomass production, it coversabout5% of the global forest with Pinus and Eucalyptus species the most commonly used in the world (FAO, 2001)
Morphological feature of fungal isolates reveals, six fungal genera belonging to Alternaria, Diplodia, Pestalotiopsis, Curvularia, Phoma, and Penicillium were the cause for the diseases symptom observed in the study areas (Figure 2)
Phoma glomerata, Alternaria Alternata and genera of Curvularia, Pestalotiopsis, and Penicillium including Diplodia were found to be the cause for symptoms observed on plantations
Summary
Plantation forests are cultivated forest ecosystems established by planting or seeding using introduced or indigenous species in the process of afforestation and reforestation, primarily for wood biomass production, it coversabout5% of the global forest with Pinus and Eucalyptus species the most commonly used in the world (FAO, 2001). Yirdaw (2002) showed that forest plantations in Ethiopia are mainly exotic genera of Eucalyptus, Cupressus, Casuarina, Pinus, and native Juniperus species. An income from plantations like Eucalyptus tree sales contributes on average up to 25% of total household annual cash income and for poor households up to 72% of the total annual cash income which is the largest non-agricultural source of household income in the country (Jegger, 2003)
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