Crop Protection

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    SURVEY OF TURCICUM LEAF BLIGHT (Exserohilum turcicum) ON MAIZE (Zea mays) AND EVALUATION OF MAIZE VARIETIES AND FUNGICIDE SPRAY FREQUENCIES FOR ITS MANAGEMENT
    (Hawassa University College of Agriculture, 2018) TAJUDIN ALIYI MOHAMMED
    Turcicum leaf blight (Exserohilum turcicum), TLB, is a major disease affecting maize (Zea mays) in western Ethiopia. This study was designed to: assess the incidence and severity of TLB in major maize growing agro-ecologies of Western Oromia, evaluate the reaction of maize varieties under production to TLB, and determine optimum propiconazole (tilt 250 EC) frequency as management option to TLB. Survey was conducted on 172 farmers’ fields in 29 districts and five zones of major maize growing agro ecologies in western Oromia region of Ethiopia. Survey results revealed the prevalence of TLB across all the districts even though at different levels. Mean TLB incidence ranged from 16.3% in Abay chomen to 96.67% in Wayu Tuka and mean percent severity index varied between 3.1% in Abay chomen and 57.5% in Lalo Assoabi district. TLB was relatively more severe on maize varieties BH-540, Limu and Kolba on surveyed areas. In addition, the effects of maize varieties, fungicide frequencies and their interactions on TLB development were assessed in a field experiment during the 2016/17 main growing season at Ambo Plant Protection Research Centre (APPRC). The experiment involved three maize varieties and three fungicide (Tilt, propiconazole) frequencies arranged in a factorial setting in randomized complete block design with three replications. TLB was initiated following artificial inoculation. Data were recorded on disease incidence and severity and severity scores were used to calculate area under disease progress curve (AUDPC) and infection rate. Grain yield and yield components were measured after harvest. Finally correlation and economic analyses were carried out. Disease parameters varied markedly across treatments, especially variety-fungicide combinations had a highly significant variation (p<0.01) in disease parameters. The highest terminal percent severity index (PSI) (86.7%), AUDPC value (2614.4 %-day) and disease progress rate (0.09339 units-day -1 ) were recorded on unsprayed variety AMHQ-760. On the other hand, the same variety had significantly lower disease level and gave the highest grain yield (9.424 t ha -1 ) when it was treated three times with propiconazole. TLB resulted in grain yield losses of up to 62.4% on AMHQ-760. PSI, AUDPC, incidence and disease progress rate were negatively correlated with yield and yield components. The highest marginal benefit (ETB 63,089 ha -1 ), and marginal rate of return (ETB 14.53) were obtained from variety AMHQ-760 with thrice application of propiconazole. Based on current results, three propiconazole applications were found effective to manage TLB even on susceptible maize variety. However, additional experiments should be carried out to verify the current results.