Fungicide strategies to manage wheat stem rust
Silvia Pereyra: National Institute for Agricultural Research (INIA)
<div>Stem rust (SR), caused by <em>Puccinia graminis</em> f.sp. <em>tritici,</em> is one of the most destructive diseases of wheat in the Southern Cone of America. The main factor contributing to this has been the increased use of susceptible cultivars. Medium-long term efforts pursue the development of adapted lines resistant to local and Ug99+races (potential risk). However, the optimization of short-term strategies comprising the use of foliar fungicides are needed to manage SR. Field trials were established in 2015 and 2016 in Uruguay to evaluate application moments of metconazole+epoxiconazole (first symptoms, ZGS65 and ZGS71) and nozzle types (CJ03®, TTJ60®) in SR susceptible (cv.B601) and intermediate (cv.B501) cultivars. Six commercial fungicides, including combinations of DMIs, QoIs and SDHIs and a non-treated and a complete treatment were evaluated in cv.B601 in both years. Fungicide application at disease onset significantly (p ≤ 0.05) reduced SR severity, AUDPC and increased grain yield, test weight and thousand-kernel weight as compared to the non-treated and applications at ZGS71. Epoxiconazole and metconazole were detected in harvested grain if applied at ZGS71. Yet, concentrations were below the maximum residue levels (CODEX and EU). Significant differences were found among fungicides for SR severity, if applied at first symptoms. These results suggest that fungicides can effectively reduce SR severity and increase grain yield in susceptible cultivars if applied at disease onset.</div>
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