Abstract
Pink rot, caused by Phytophthora erythroseptica, can result in substantial field and storage losses in potato, and reduced sensitivity to mefenoxam has increased the need for alternative chemistries. Seven randomized complete block field trials were conducted from 2018 to 2024 at Aberdeen Research and Extension Center, Idaho, using inoculated plots of the susceptible cultivar Russet Burbank to evaluate seed, in-furrow, and foliar fungicide programs for in-season management of pink rot. Programs included oxathiapiprolin + mefenoxam (Orondis Gold) applied in-furrow and/or foliarly, phosphite (Phostrol), mefenoxam + chlorothalonil (Ridomil Gold Bravo), cyazofamid (Ranman), and a seed treatment program (CruiserMaxx Vibrance + Revus) compared with an untreated check. Emergence, expressed as the relative area under the emergence progress curve (RAUEPC), varied among years but was not affected by fungicide program, indicating no adverse effects on stand establishment. In contrast, fungicide programs significantly reduced pink rot in the field and in storage across years. Orondis Gold–based programs and phosphite provided the largest and most consistent decreases in rot, typically reducing field rot by 15 to 18 percentage points and storage incidence and severity by 25 to 33 percentage points relative to the untreated check. Programs containing Orondis Gold or Ridomil Gold Bravo also increased total yield by 2.0 to 3.6 tonnes/ha, whereas the phosphite program, despite strong disease suppression, did not consistently improve yield. Overall, oxathiapiprolin-based programs, used alone or in combination with mefenoxam, offered the most reliable in-season control of pink rot and the greatest yield benefits under Idaho field conditions.