A review of coffee wilt disease, Gibberella xylarioides (Fusarium xylarioides) in Africa with special reference to Ethiopia

Coffee is vital to the economy of East and Central Africa,providing a major source of foreign exchange earnings and as a cash crop,supporting the livelihood of millions of people who are involved in cultivation, processing, marketing, and export. Coffee is attacked by variousdisease-causing organisms such as fungi, bacteria, viruses, nematodes, insects and weeds. One of the limiting factors for coffee production in Central and East African countries is tracheomycosis/vascular wilt disease caused by Fusarium xylarioides Steyaert imperfect stage (Gibberella xylarioides Heim and Saccas perfect stage). Coffee production and development is now threatened by coffee wilt disease (CWD). The major difference between tracheomycosis and many other coffee diseases is that it kills all affected trees at all stages of growth. Coffee wilt disease was first observed in 1927 in a plantation of Coffea excelsa, in the Central African Republic. Since then, CWD has re-emerged on C. canephora/excelsa in portions of the Democratic Republic of Congo in the mid-1980s, it affected up to 90% of plantations in 1993 in Uganda. The fungus lives in the soil, on infected debris, in alternative hosts or as resistant propagules of species, and enters the coffee tree through wounds at the base of the tree or on the roots. The outbreak of the pathogen has been reported throughout the major coffee-growing woredas in the south and south western parts of Ethiopia. The disease infestation incidence varied between 14.9 and 34.0%. The estimated annual coffee yield losses caused by CWD are about 7.4%, 1.6% and 2.6% in Uganda, Ethiopia and Tanzania, respectively. CWD is distributed, and caused coffee yield losses in major coffee-growing areas of western, southern and eastern parts of Ethiopia. The mean disease incidence ranged from 45% at Gera to 69% at Bebeka, with certain variations between coffee fields at each locality. The pathogen survives in the soil. It is difficult to control the pathogen by fungicides. However, the pathogen may be controlled by antagonistic biological control agents. In vitro evaluation of Trichoderma species has revealed up to 71% reduction of the mycelial growth of coffee wilt pathogen (F. xylarioides).