Demand-Driven Technologies for Sustainable Maize ... - IITA

243Present status of maize diseases in the humidforest and western highlands of CameroonZ. Ngoko 1 , K.F. Cardwell 2 , W.F.O. Marasas 3 , P. Tchamo 1 , A. Tagne 1 ,M. Mwangi 4 and M.J. Wingfield 51IRAD Bambui, Bamenda, Cameroon2National Program Leader, Plant Pathology, Cooperative State Research, Educationand Extension Service, US Department of Agriculture, Washington DC3Programme on Mycotoxins and Experimental Carcinogenesis, Medical ResearchCouncil, Tygerberg, South Africa4IITA, Ibadan , Nigeria5Faculty of Biological and Agricultural SciencesForestry and Agricultural Biotechnology Institute, University of PretoriaPretoria, South AfricaAbstractMaize disease surveys were conducted between 1995 and 2004 inthe Republic of Cameroon. A total of 260 farms in 36 villages, rangingfrom low altitudes with bimodal rainfall distribution to high altitudeswith monomodal rainfall, were included in the surveys. In the humidforest, Bipolaris maydis and Puccinia polysora were the prevalentfungi with a mean incidence of 70% in 1995 and 44% in 2004.Rhizoctonia solani, Stenocarpella macrospora, and Physoderma maydisoccurred at low incidence levels in all the villages. In the westernhighlands, Exserohilum turcicum and Cercospora zeae-maydis were theprevalent pathogens, with incidence ranging from 16% to 100% in1995–1998. In 2004, the mean incidence for the pathogens rangedfrom 30 to 95%. Phaeosphaeria maydis, the most severe pathogen(incidence=70%) in 1995, has been displaced by Cercospora zeaemaydis(incidence=60%). The incidences of Sporisorium reilianum andPuccinia sorghi were about 5% in 1998; in 2004, the incidence of S.reilianum had increased to 20%. In many of the farms surveyed, most ofthese diseases occurred in association. There was a positive correlationbetween incidence of Puccinia polysora and that of Bipolaris maydis inthe humid forest. Phaeosphaeria leaf spot was negatively correlatedwith C. zeae-maydis and E. turcicum in the western highlands. Althoughsome diseases were prevalent in specifi c ecological niches, E. turcicumwas found in both highlands and lowlands but with low incidence inthe latter areas. Fusarium, Aspergillus species and Diplodia maydis werethe most important mycotoxin-producing fungi that caused ear rots inthe western highlands in 2004.