Evaluation of foliar fungicides for Cercospora leaf spot management in table beet in New York

Abstract

Cercospora leaf spot (CLS), caused by the fungus, Cercospora beticola, is a major constraint to table beet production in New York (NY). The disease causes defoliation, negatively impacting harvests using top-pulling machinery and rendering plants unsuitable for fresh market sales. High genetic diversity within C. beticola populations can result in the rapid development of resistance to single-site mode of action fungicides. Therefore, products with multiple modes of action and/or differential site-specific modes of action are highly desirable to improve the resiliency of CLS management. In 2021 and 2022, small plot replicated trials were conducted to evaluate the efficacy of selected fungicides for CLS management in table beet at Geneva, NY. Propiconazole, pydiflumetofen + fludioxonil, and copper hydroxide were the most efficacious for CLS management and not significantly different between each other. Across these treatments, CLS severity was reduced by 72.8% and 78.6% compared to nontreated plots in 2021 and 2022, respectively. Trifloxystrobin + fluopyram, pyrimethanil + fluopyram and pyraclostrobin + fluxapyroxad provided moderate disease control with an average reduction of 45.4% and 56.7% in CLS severity in 2021 and 2022, respectively. Trifloxystrobin and a proprietary copper + zinc (Cu/Zn) compound at two rates (0.25% and 0.5% v/v) also significantly reduced CLS severity by 20.1% in 2021 but not in 2022. Improvements in foliar health through reduced CLS severity had no significant effect on root shape, size, color, and sugar content. This information underpins best management practices for foliar health leading to economic and sustainable outcomes for table beet producers.