Fungicide Field Treatments to Control Potato Leak Caused by Pythium ultimum

Potato leak, caused by Pythium ultimum , is characterized by brown to dark-gray lesions on tubers. The efficacy of fungicides applied by foliar spray, in-furrow treatment, or by combination of both methods on disease incidence was evaluated in three field trials. In 2018, a single [50 days after planting (DAP), or 1 week prior to haulm kill (HK)], or two foliar sprays (50 DAP and 1 week pre-HK) of metalaxyl, hymexazol and propamocarb-HCl were evaluated. Disease incidence was significantly reduced only by metalaxyl. In 2019 trials, only metalaxyl treatments were included: a single (50 DAP; 2-weeks pre-HK; 2-days post-HK) or two foliar sprays (50 DAP; 2-weeks pre-HK), in-furrow treatment, alone or combined with foliar spray (2-weeks pre-HK). Disease incidence was significantly reduced by all treatments, except for foliar spray 50 DAP (only in Exp C). The lowest incidence was observed in the in-furrow treatment alone or combined with foliar spray applied 2-weeks before HK.