P-110 - A five-year study on in-season management of pink rot in potatoes.

Pink rot, caused by the soil-borne fungus Phytophthora erythroseptica, is a significant disease impacting potatoes in the USA and globally. Although it typically occurs in wet fields, it can also develop in sandy soils without excessive moisture. Infection is favored by factors such as highly infested soil, high temperatures at harvest, wounds and bruises during harvest, and high humidity in storage. If infected tubers are stored under conditions of high humidity with poor ventilation, substantial losses of stored potatoes can occur. Mefenoxam, a highly effective systemic fungicide, has been used for many years to manage oomycete pathogens in potatoes, including P. erythroseptica and Pythium ultimum. However, resistance to mefenoxam is becoming increasingly common in P. erythroseptica in the United States. Fortunately, a new product, oxathiapiprolin, has recently been registered in Idaho for use on potatoes to control oomycete diseases such as pink rot. To determine the optimal application timings of oxathiapiprolin for pink rot control, randomized complete block spray trials were conducted over five years. Various application timings of both oxathiapiprolin and mefenoxam were studied to identify the most effective schedules for pink rot control. The results indicated that applying oxathiapiprolin in the furrow or foliarly when tubers reach a diameter of 2-3 cm provided effective control of pink rot during storage. These findings highlight the efficacy of new product chemistries in managing pink rot.