Agricultural producers are facing increasing pressure to reduce the use of fungicides, for which deployment of cultivars with disease resistance is one viable solution. Accordingly, several sources of resistance to major crop diseases have been identified and introgressed. For example, in grapes the two most important foliar diseases, powdery mildew and downy mildew, can be suppressed by resistance genes identified from wild sources (Blasi et al. 2011; Feechan et al. 2013; Mahanil et al. 2012; Ramming et al. 2011). Once genetic control of major diseases and the subsequent reduction in fungicide applications is achieved, other problems may emerge, namely pathogens that were secondary targets of routine fungicide applications. This phenomenon has been observed in powdery and downy mildew-resistant vineyards, where the incidence of grapevine black rot increased (Molitor and Beyer 2014; Rex et al. 2014).