Fenbuconazole, a broad spectrum triazole fungicide with restricted uptake and consequent redistribution within wheat plants, has been perceived to possess limited curative properties when formulated as a suspension concentrate (SC). Field and greenhouse studies demonstrated that curative and to a lesser extent protectant activity of fenbuconazole on wheat leaf rust (Puccinia triticina) and stripe rust (Puccinia striiformis f.sp. tritici) was improved by the addition of the adjuvant Uptake™ Spraying Oil (Uptake is a trademark of Dow AgroSciences). The purpose of this study was to determine if the addition of adjuvant increased penetration of fenbuconazole into wheat tissue and if this was correlated with enhanced redistribution within the plant and the observed increase in activity. These data confirm that the addition of adjuvant improved penetration of fenbuconazole into wheat leaves and was responsible for the observed increase in biological activity of the fenbuconazole suspension concentrate formulation. In addition, adjuvant decreased the amount of material washed off with water a result suggesting the potential for improved rain-fastness in the field. Fenbuconazole's fungicidal activity against cereal rusts could be limited by poor penetration into plant tissue unless a suitable adjuvant is incorporated into the spray solution. Accepted for publication 31 January 2013. Published 28 May 2013.