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

246Field surveysField surveys were conducted in June of 1995, 1996 and 1997. The1995 survey was conducted in four HF villages (Nkometou, Ngat,Etoud, and Mvoutessi III). In 1996, the survey was repeated in three ofthe HF villages (Nkometou, Ngat, and Etoud) and three WHL villages(Bamunka, Bali, and Njinikom). In 1997, the survey was repeated in thesame WHL villages. Thus, in each of the two ecologies, three villageswere surveyed for two consecutive years. In each village 12 farmerswere selected at random with the assistance of the extension agent ofthe locality. The survey team, which consisted of a plant pathologistand an entomologist, visited a total of 108 farmers’ fi elds. In eachfarm, 15 maize plants at growth stages 6 to 9 as described by Hanway(1966) were chosen at random. Each plant was assessed for growthand damage.Data on the following variables were recorded: cropping system;organic matter rating on a 1-3 scale (1= low, 2 = medium, 3= high);soil texture rating on a 1-3 scale (1= sandy, 3= clayey); weediness(1-3 scale: 1=clean and 3=very weedy); crop growth stage (1-9scale: 1= emergence, 5=silking, 7=milk stage, 8=hard dough and9=physiological maturity); stem diameter (determined by measuringthe diameter of the second internode above the ground); percentagegrain fi ll; % cob damage by fungi; width and length of cobs andweight of dehusked cobs. The disease data included the etiologyand severity of infection (1-5 scale: 1=clean and 5=heavily infectedplant) of at least the two most important diseases per plant. Leafsamples infected with highland blight [Exserohilum turcicum (Passerini)Leonard & Suggs], and lowland blight [Bipolaris maydis (Nisikado &Miyake) Shoemaker], were incubated on PDA for confi rmation ofthe identity of the causative fungi. Symptoms of Diplodia leaf spot(Stenocarpella macrospora (Earle) Sutton = Diplodia macrosporaEarle), common smut (Ustilago maydis DC), head smut [Sporisoriumreilianum (Kühn) Langdon & Fullerton = Sphacelotheca reiliana (Kühn)Clint], Phaeosphaeria leaf spot [Phaeosphaeria maydis (P. Henn) Rane,Payak & Renfro], highland rust (Puccinia sorghi Schw.), lowland rust(Puccinia polysora Underw.), brown spot (Physoderma maydis Miyabe)and sheath blight (Rhizoctonia solani Kühn) were compared to thosedescribed in the Compendium of Maize Diseases. Grey leaf spot wasidentifi ed according to Latterell & Rossi (1983). The disease incidenceof each location consisted of the total number of infected plants perlocation over 180 plants. Fungal stem infections and proportion oftotal leaf area infected (% LAI) with diseases were calculated accordingto Clive (1971). The general phytosanitary condition of the fi eld wasalso assessed and incidence of diseases that prevailed on maize plantsother than those sampled was recorded. In this paper, only the data