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Foliar Fungicides to Control Wheat Stem Rust, Race TTKS (Ug99), in Kenya

The emergence of a new virulent race of stem rust (Puccinia graminis f. sp. tritici) of wheat (Triticum aestivum), TTKS (Ug99), calls for urgent measures to contain the disease, which is a serious threat to wheat production in Kenya. Nine commercial fungicides were evaluated for control of stem rust in the field in three locations in 2005 and 2006. Ten treatments, including untreated control, were applied on field plots in a randomized complete block design with four replications. Assessment of stem rust severity was done at growth stage (GS) 55 (heading), GS 65 (flowering), and GS 75 (late milk) and expressed in terms of mean rust severity and area under the disease progress curve (AUDPC). In general, fungicide treatment significantly (P ≤ 0.05) reduced rust severity, AUDPC, and losses in grain yield and 1,000-kernel weight for cv. Duma compared with the untreated control. Stem rust was severe in both years across all sites, resulting in significantly less grain yield in the control treatment. The 1,000-kernel weight was significantly less at two locations in 2006. Fungicides azoxystrobin at 200 g/liter + cyproconazole at 80 g/liter (AmistarXtra 280 SC), tebuconazole (Folicur 250 EC), tebuconazole + tridimenol (Silvacur 375 EC), and tebuconazole (Orius 25 EW) were more effective in reducing stem rust across the sites. Fungicides trifloxystrobin + propiconazole (Stratego 250 EC), hexaconazole (Cotaf 5 EC), epoxiconazole + carbendazim (Swing 250 EC), cyproconazole at 80 g/liter + propiconazole at 250 g/liter (Artea 330EC), and epoxiconazole at 125 g/liter + carbendazim at 125 g/liter (Soprano C 250 EC) were inconsistent in the reduction of the disease. The results suggest that fungicides can be used effectively in reducing stem rust severity and increasing yield of susceptible wheat cultivars in stem-rust-prone areas.