A decade of European monitoring studies on fluopicolide sensitivity of Phytophthora infestans and performance of Infinito® against Potato Late Blight

Phytophthora infestans is a hemibiotrophic oomycete pathogen that causes Late Blight disease in important Solanaceae crops worldwide, including potatoes. The pathogen can infect leaves, stems and tubers of potato plants, leading to substantial yield losses during cultivation and storage. To prevent local infections leading to widespread epidemics, oomyceticides are widely used. In 2006, fluopicolide, an inhibitor of the vacuolar H ⁺ -ATPase, was registered in Europe and introduced to the potato market together with propamocarb in the mixture product Infinito ^® . In this study, fluopicolide sensitivity data for 460 P. infestans isolates was summarized for the years 2013 to 2023, originating from different countries in Northern-, Central- and Southern European. For fluopicolide, presence of field resistant strains has not been observed until now in European Late Blight monitoring programs. In addition, greenhouse efficacy trials with the mixture product Infinito ^® were conducted testing the dominant sub-populations of P. infestans of the last decade: EU_13_A2, EU_33_A2, EU_36_A2, EU_37_A2, EU_41_A2, EU_43_A1 and EU_46_A1. All experiments showed a high efficacy of Infinito ^® (70–99%) comparable or better than the market standard fluazinam (Shirlan ^® , 0–97%). In combination, these results highlight the reliable efficacy of fluopicolide based products to control P. infestans , independent of the European sub-population. In general, proactive resistance management strategies were implemented to prevent occurrence of fluopicolide-resistant strains. Infinito ^® should not be used in more than two consecutive applications. Also, Infinito ^® should not be applied more than four times or more than half (50%) of the total number of fungicide applications per season.