Epidemics of stripe rust (Puccinia striiformis) on common wheat (Triticum aestivum) in the highlands of Bale, southeastern Ethiopia

The effects of common wheat cultivars and fungicide (triadimefon) spray intervals (at 7-, 14-, 21-, 28-d, and no spray) on the temporal epidemics of stripe or yellow rust caused by Puccinia striiformis f.sp. tritici were studied. The experiments were conducted in the main cropping seasons (August–December) in 2002 and 2003 at Agarfa and Sinana in Bale highlands, Ethiopia. Severity, disease progress rate (r), and area under disease progress curve (AUDPC) were used to evaluate the effects of the treatments. The spray intervals significantly affected disease severity and varied the rate of epidemic development. Stripe rust epidemics varied significantly between locations, seasons, and among cultivars. The disease developed at a rate of 0.173–0.244 units per day on the susceptible cv. Wabe, 0.155–0.231 on the moderately resistant cv. Mitike, and 0.06–0.143 on the resistant cv. Madda-Walabu under natural disease epidemics. The severity and rate of stripe rust progression were significantly influenced by resistance of the cultivars. Fungicide application significantly reduced stripe rust severity and AUDPC by reducing its progress rate on the susceptible cultivar. Grain yield harvested from sprayed plots was consistently greater than the yield harvested from unsprayed plots.