Interaction between cultivar and fungicide program for control of early blight, brown spot, and white mold.

Wednesday, July 28, 2021
3:05 PM - 3:25 PM

Early blight, brown spot, and white mold are the most common foliar diseases in southern Idaho and can cause significant yield reductions if not managed. Russet cultivars differ in their susceptibility to these foliar diseases, but work has not been done evaluating how this variation in susceptibility would affect the performance of a standard fungicide program. Field trials were conducted in 2019 and 2020 on eight russet-type potato cultivars (Burbank, Ranger, Norkotah, Umatilla, Alturas, Clearwater, Teton, and Dakota) to compare the performance of a standard fungicide program against foliar diseases. The trial was arranged as a two-way factorial with four replications. The fungicide program consisted of fluopyram + pyrimethanil tank-mixed with chlorothalonil twice, followed by two applications of chlorothalonil. Fungicide applications were initiated just prior to row closure and repeated on a two-week interval for four total applications. Early blight and brown spot severity were visually rated together and the number of white mold lesions were counted from all plants in the center two rows of each four-row plot. Norkotah and Teton were the most susceptible to early blight/brown spot and Alturas, Dakota, and Clearwater were the most resistant. The fungicide program was highly effective in reducing early blight/brown spot on all cultivars, however, a stronger program may provide greater control with Teton and Norkotah. Alturas, Ranger, and Norkotah were the most susceptible to white mold and Dakota and Teton were the most resistant. The fungicide program was effective on all varieties for reducing white mold incidence. This standard fungicide program used by many growers in southern Idaho is effective in managing the three primary foliar diseases evaluated in this trial. However, a reduction in fungicide use may be possible for some cultivars. Additional field research is needed to see if these program alterations would be effective.
Grower-oriented session