Control of potato powdery scab with fluazinam, cyazofamid or bupirimate under field conditions in China

The soilborne pathogen Spongospora subterranea f. sp., which is subterranean and responsible for powdery scab, poses a serious threat to potato production in China. Single applications of fluazinam, cyazofamid and bupirimate via furrow application or seed dressing during the sowing period and combined application with root irrigation during the tuber initiation stage were assessed for their ability to control powdery scab under field conditions. Three field trials revealed that fluazinam or cyazofamid furrow application at 1500 g a.i. ha⁻¹ during the sowing period combined with root irrigation at 1500 g a.i. ha⁻¹ during the tuber initiation stage significantly reduced the disease incidence and disease index of potato powdery scab, with good control efficacy (58.1–79.4% and 53.1–78.5%, respectively), and provided high potato yields (3.37–5.08 kg m⁻² and 3.26–4.88 kg m⁻², respectively) and gross revenue for growers. However, due to the low price of potato and high control cost, the two selected promising chemical treatments have few advantages in terms of economic benefits. Overall, considering their control efficacy and economic benefits, fluazinam or cyazofamid furrow application combined with root irrigation treatment could be recommended for integrated powdery scab management, especially for high-value seed potato production in China.