植物病理学および微生物学ジャーナル

概要

Coffee Thread Blight (Corticium koleroga): a Coming Threat for Ethiopian Coffee Production

Kifle Belachew, Demelash Teferi and Legese Hagos

Besides its importance coffee production constraints with number biotic factors of which diseases are major. Coffee is prone to a number of diseases that attack fruits, leaves, stems and roots, and reduce yield and marketability. Major coffee diseases in Ethiopia are Coffee berry diseases (Colletotrichum kahawae), Coffee wilt disease (Gibberella xylarioides) and coffee leaf rust (Himalia vestatrix) however, the rest diseases considered minor. Thread blight of coffee caused by Corticium koleroga is an important disease of Coffee in India. Thread blight diseases in Ethiopian coffee for first time recorded at Gera and Metu agricultural research sub-stations in 1978. However it sporadically occurs between June and September, but becoming important at high land coffee growing areas of southwestern, Ethiopia. Investigations including diagnostic surveys for assessing the disease occurrence, prevalence, incidence and severity was conducted and the sample was brought to Plant Pathology Laboratory of Jimma Agricultural Research Center. The results of study showed that the disease syndrome on detached coffee plants were similar with thread blight of coffee recorded so far and observed at the field. The disease invariably attacks coffee leaves, branches, twigs and berries with characteristic blight symptoms. White fungal threads were seen on the young stems and succulents tender tissues of coffee trees. These threads eventually become dark brown in color grow and spread to cover underside of leaves while coffee berries on infected braches are also completely destroyed leading to total crop failure. The isolation and identification of the causal pathogen from samples of leaves, berries, branches and shoots consistently produced fungal species which may be Corticium koleroga that further proved by pathogenicity tests. The disease mean incidence and severity during first outbreak (2008) at Limmu coffee plantation farm of “Gummer” was 49.02 and 9.8%, respectively. The second reported outbreak of the diseases was from Bebeka coffee estate of “Disadis” farm (2012). Current area wide outbreak at major coffee growing areas of southwest, west and south Ethiopia was in 2014 with mean incidence and severity of 58.44 and 32.59%, respectively, resulting in considerable damages. Among others, climatic factors prolonged rainfall with long period of wet favored the thread blight disease outbreaks implicating the present climate change scenarios are favoring challenging diseases on Arabica coffee production in Ethiopia.