Management of Common Bean Rust ( Uromyces appendiculatus ) through Host Resistance and Fungicide Sprays in Hirna District, Eastern Ethiopia

Common bean rust (Uromyces appendiculatus) is an important disease affecting common bean (Phaseolus vulgaris L.) production in the world. In Ethiopia, this is the most destructive disease constraining common bean production. Field experiments were carried out at Hirna Research Sub-Station of Haramaya University in the 2010 main cropping season to elucidate reaction of released common bean varieties to rust infection and to study the effect of integrated use of host resistance and fungicide foliar sprays on incidence of the disease and its control. For the evaluation of common bean varieties to rust disease the experiment was laid out in randomized complete block design with three replications and 15 varieties and the experiment was laid out as a randomized complete block design in factorial arrangement with three replications for the management part. In the fungicide spray, three contact (i.e., Chlorothalonil, Mancozeb and Copper hydroxide) and one systemic (Triadimefon) fungicides were tested on a susceptible (Mexican-142) and a moderately resistant (Awash-1) varieties. The research results obtained indicated that the evaluated common bean varieties varied significantly in severity, area under disease progress curve, disease progress rate and grain yield. Three reaction groups of common bean varieties were identified, viz. susceptible, moderately resistant and resistant. The resistant varieties produced the highest grain yield. At Hirna the varieties, Kufanzik, Haramaya, Melkadima, Gofta, Chore and Awash Melka were found to be resistant to the disease. These varieties were also high yielders. However, in case seeds of resistant varieties are inadequate to cover the major growing areas, farmers can use the moderately resistant varieties with fungicide sprays wherever the disease is a pervasive and pressing problem. In the management study, lower rust incidence, severity, area under progress curve and slower disease progress rate occurred on the moderately resistant variety sprayed with Triadimefon than on the susceptible variety with Triadimefon and/or with other fungicides (Mancozeb, Copper hydroxide and Chlorothalonil). The integrated use of moderately resistant variety (Awash-1) with Triadimefon proved to be the best management option producing the highest (2306.25 kg ha-1) grain yield. Triadimefon foliar spray reduced relative grain yield loss by 10.84% on the moderately resistant variety Awash-1 compared to the susceptible variety Mexican-142. In conclusion, integrated use of Awash-1 with Triadimefon spray was found to be the most effective bean rust management option.