Potato mop-top virus (PMTV), a necrotic virus of potato, and its vectorSpongospora subterranea (Ss), which causes powdery scab, are growing threats to North American potato production. These two soil-borne pathogens are limiting the production of healthy tubers and are negatively impacting seed and fresh market potato exports. The biphasic life cycle of Ss and the durability and viability of its resting spores makes disease management particularly difficult. We investigated the effects of two chemicals, Omega^®500F and FOLI-R-PLUS RIDEZ^TM, on powdery scab and PMTV and on the reduction of Ss inoculum in naturally infested fields and potting mix using different potato cultivars. There was no significant difference related to chemical treatments on the amount of Ss inoculum in the soil or potting mix nor on PMTV incidence. Ss soil inoculum in fields varied across farms and among potato cultivars. Russet cultivars were more tolerant to powdery scab than the yellow- or red-skinned cultivars. However, PMTV incidences on tubers collected from Classic Russet and Russet Norkotah 8 ranged from 0 to 80%, even though the tubers lacked powdery scab lesions. In addition, 93% of plants were infected by PMTV in the greenhouse, indicating PMTV transmission was high under optimal conditions for powdery scab disease development. These results expand our current understanding of powdery scab and PMTV and aid in development of integrated management practices for these important diseases.