Two field experiments were conducted in New Brunswick, Canada, in 2020 and 2021 to test the efficacy of various fungicides, soil amendments, and plant byproducts in managing powdery scab ( Spongospora subterranea f. sp. subterranea) of potato ( Solanum tuberosum) in previously infested potato fields. Disease-free ‘Calwhite’ potato seed was used. In 2020, 14 treatments were used, including fungicides, biostimulants, and fertilizers. Treatments did not affect emergence or vigor. Fluazinam single dose (1×) and double dose (2×), mancozeb single dose (1×), or cyazofamid in-furrow significantly reduced the percentage of diseased tuber weight (%DTW) by 70.3, 62.6, 54.9, or 75.1% and increased marketable yield (MY) by 22.1, 26.5, 41.6, and 30.5%, respectively. Boron significantly reduced %DTW by 66.9% and increased MY by 23.9%. The trial was repeated in 2021 using nine treatments. In-furrow fluazinam, mancozeb, or cyazofamid reduced %DTW by 43.7, 39.7, or 54.4% and increased MY by 75.5, 57.0, and 65.9%, respectively. Boron also significantly increased MY. The second-year trial confirmed that in-furrow application of fluazinam, mancozeb, or cyazofamid is more suitable in managing powdery scab and increasing MY in disease-infested fields, and boron soil treatment is a promising alternative for chemical treatments. The difference in MY is solely due to the powdery scab disease severity.
Khalil I. Al-Mughrabi (Tue,) studied this question.