Plant pathogens and their hosts are in engaged in a struggle to control the course of infection, and whether the outcome results in disease or immunity. Pathogens such as Phytophthora sojae, which is the cause of soybean root rot, secrete effectors to promote their own growth and reproduction. In turn, host plants deploy immune receptors for surveillance and detection of the effectors. Epigenetic switching of effector gene expression states could explain past observations of spontaneous virulence changes occurring in the laboratory and in the field. Epigenetic control of effector genes potentially offers pathogens the ability to re-activate or recycle effectors in response to changes in host immunity or after hard selective sweeps. Much remains to be discovered regarding the mechanisms of epigenetic control but operationally the phenomenon helps to answer longstanding questions. Evolution may favor systems that allow pathogens to evade host immunity by reversible modulation of effector gene expression states.