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

251Table 6. Mean disease severity ratings (1-5 scale)* and leaf area infected(LAI) by maize pathogens in the WHL of Cameroon in 1995 and2004.PathogensLocationsBali Njinikom Bamunka95 04 95 04 95 04 MeanE. turcicum 3.5a 2.3b 3.6a 3.3a 3.0a 2.8a 3.1C. zeae-maydis 3.5a 3.5a 3.1a 3.9b 3.6a 2.6b 3.4Phy. maydis 1.9a 2.9b 1.0a 2.2b 1.0a 2.6a 1.9Stem disease 1.0a 1.6b 1.1a 1.6b 1.2a 1.9a 1.4Pha. maydis 1.0a 2.1b 1.0a 2.5b 1.0a 2.1a 1.6S.macrospora 0.7 - - - - 0.6 -LAI 18.9a 3.5b 18.2a 33.2b 12.8a 8.3b 15.8*Means followed by the same letter in rows within location are not significantly different (P< 0.05).E = Exserohilum; C = Cercospora; Phy. = Physoderma; Pha. = Phaeosphaeria S= Stenocarpella.- = not recorded.Table 7.Correlation matrix between leaf area infected (LAI) and individualpathogens in the WHL of Cameroon in 1995.LAI Cz EtLAI 1.00C. zeae-maydis 0.65*** 1.00E. turcicum 0.39*** 0.2*** 1.00Cz= Cercospora zeae-maydis; Et = Exserohilum turcicum; C= Cercospora; E= Exserohilum*significant at P=0.05; ** significant at P=0.01, *** significant at P=0.001In 2004, in the WHL, E. turcicum, Phaeosphaeria maydis, and C.zeae-maydis had signifi cant (P=0.001) positive, and S. macrosporasignifi cant (P=0.01) negative correlation coeffi cients with LAI (Table 8).Negative correlations existed between E. turcicum and S. macrosporaand C. zeae-maydis, as well as between C. zeae-maydis andphysiological spot and Physoderma maydis, but the former increasedwith Phaeosphaeria maydis. Ear rots (Fusarium ssp. and Diplodia spp.)were a serious threat to maize harvested late in the WHL in 2004(Table 9).Diseases recorded in 2004, were similar to those recorded theprevious years with high incidence of ear and stalk rots due to Fusariumspp. and Diplodia spp., particularly in Noun (20%), Mifi (10%), andMenoua Division (10%).DiscussionDetailed disease surveys conducted in different parts of Cameroonfor selected years between 1995 and 2004 showed that P. polysora,B. maydis and S. macrospora were the most prevalent diseases in theHF while C. zeae-maydis and E. turcicum were the predominant maizediseases in the WHL. Generally, P. polysora was found more frequently