Multi-environment assessment of fungicide performance for managing wheat head blast (WHB) in Brazil and Bolivia

This study aimed to evaluate the performance of fungicides against wheat head blast (WHB) under various environments and to determine scenarios best suited for fungicide applications. Field experiments were conducted at 23 environments in Brazil and Bolivia from 2012 to 2015. Data from all trials within the same country were combined for estimating mean WHB control efficacy and yield benefits from using a set of fungicides. Experiments were classified, based on disease index in the check treatment, as having low (CDI=10), moderate (CDI=40), and high (CDI=70) disease pressure and this variable was tested as a covariate in the model. In Brazil, greater disease reduction and yield increase, in trials with moderate to high disease pressure, were obtained when using mancozeb-based fungicides, but with yield gains below 1276kg/ha. In Bolivia, all fungicides reduced the disease at moderate to high disease pressure, but specific QoI+DMI premixes led to higher yield gains averaging 1834kg/ha. Based on the evidence provided, we concluded that current WHB chemical strategies could have radically different results depending on country and disease pressure. Although WHB chemical control can be effective even under environmental conditions that favor the disease, integrated management strategies should be explored. Our results are useful for aiding decisions on fungicide application and identifying priorities for future research.