Studying PIWIs in three dimensions: agronomic, economic and ecological evaluation of 14 fungus-tolerant cultivars in Luxembourg

Abstract

Growing fungus-tolerant cultivars (PIWIs) reduces the need of fungicide use by 50-80 %. PIWIs have the potential to address climate change adaptation and mitigation simultaneously. However, despite the obvious advantages of PIWI cultivation only 0.5% of the viticultural area in Luxembourg is covered with PIWIs at present. Consequently, the present investigations aimed at addressing knowledge and experience gaps of PIWI cultivation and quantifying their economic and ecological advantages.

The project PIWI3 characterizes 14 PIWI cultivars in three dimensions: (1) agronomically, (2) economically and (3) ecologically for the years 2023-2025. White and red PIWIs are compared to the traditional cultivars Rivaner and Pinot Noir, respectively. The present study focuses on the susceptibility of selected cultivars towards major fungal diseases such as powdery and downy mildew, gray mold and black rot. Furthermore, susceptibility to Drosophila suzukii is monitored as well as average yield and the phenological development. To evaluate the ecological impact, a life cycle assessment is undertaken and costs per ha are evaluated.

Weather conditions in 2024 resulted in severe disease pressure. Disease severities recorded for downy and powdery mildew differed between the PIWI cultivars. Sauvignac, Johanniter and Cabernet Blanc showed high disease severities of black rot. The onset of Botrytis cinerea epidemics was observed later in PIWI cultivars than in the traditional cultivars. The cvs Pinotin, Calardis Blanc and Villaris showed the highest bunch rot disease severities prior to harvest in 2024. However, in cv Pinotin bunch rot symptoms were mainly caused by sour rot, due to the infestation with D. suzukii.

Phenological development differed widely within the PIWI cultivars. The PIWIs studied here were generally ripening earlier compared to the traditional cultivars Rivaner and Pinot noir. The earliest cultivar reaching full maturity was cv Solaris. The highest average yield was observed for cv Bronner.

Cultivation of PIWIs reduced the overall environmental impact by two-thirds, compared to the cultivation of traditional cultivars. The reduced need of pesticide applications decreased the total annual costs of production by 56-62%, making PIWIs a viable and sustainable alternative for winegrowers.

Acknowledgements

We thank the Ministry of Agriculture, Food and Viticulture for supporting the project PIWI3.