Since 2006, an increasing number of French vineyards have chosen to convert to organic farming. One major change in vineyard practices includes replacing chemical pesticides with copper and sulfur-based products in line with Council Regulation (EC) No. 834/2007. This change can make overall management and pest and disease control more difficult and potentially lead to yield losses. From 2013 to 2016, a network of 48 vineyard plots, in southern France, under conventional management and in conversion to organic farming were monitored throughout the three-year conversion phase to investigate the grapevine phytosanitary management of four major pests and diseases and variations in control efficiency. The severity of downy and powdery mildew, grape berry moths, and Botrytis bunch rot were assessed and linked to the protection strategy. The findings showed that pests and diseases were controlled in the third year of conversion at similar efficiency levels as in conventional farming. However, the first two years of conversion were a transitional and less successful period during which higher incidences of cryptogamic diseases were observed. This demonstrates a need for winegrowers to receive more in-depth technical advice and support, especially on pest and disease control, during this critical transition period.

Given the need to reduce pesticide use and rising consumer demand for healthy food, organic vineyard areas have increased since 2000. Converting to organic farming requires numerous changes in pest and disease management, fertilization and weeding techniques. These changes can lead to difficulties in sustaining yields. Some studies have highlighted higher yields in conventional farming than in organic agriculture, but knowledge on yield dynamics during conversion is lacking. A set of 26 plots, under conventional management and in conversion to organic farming, were monitored from 2013 to 2016 in southern France throughout the three-year conversion phase to investigate the dynamics of grape yield and yield components. The survey showed that the yield and yield components remained similar levels as in conventional farming from the third year of conversion. However, the first two years of conversion were a transitional and less successful period during which yield and yield components decreased. Based on the in-depth analysis of the yield components, we have put forwards hypotheses on the processes at play and technical advice that could support winegrowers as they convert to organic farming.

Conversion to organic farming can require deep technical changes that can be implemented through various pathways. This study aimed to better understand and characterize the various pathways that can be followed during conversion to organic farming. Our results highlight four types of trajectories of technical changes that depend on the number and type of technical changes implemented. These trajectories have been associated with four strategies on equipment, labor and vineyard area. Finally, we claim that the study developed herein can support the further understanding of the strategies to be applied for successful agroecological transitions.

Grapevine decline, a major global viticulture issue, is defined as a multi-year decrease in vine productivity and/or increase in vine mortality. Although grapevine trunk diseases are one of the most-studied causes, decline is multifactorial and associated with more than 70 factors, including abiotic and biotic hazards. With so many factors to consider, the phenomenon difficult to understand, especially for winegrowers. Our study aims to make it easier to determine and assess grapevine decline by focusing on three key indicators: yield, mortality and vegetative vigour. We investigated the relationships between these indicators from both a temporal and spatial perspective to propose a set of diagnostic indicators. Thus, we conducted a winegrowers’ survey, an historical analysis of grapevine decline and field measurements of the abovementioned indicators on plot networks in three major French winegrowing regions (see graphical abstract): Bordeaux, Cognac and Languedoc. We found that farmers’ perceptions of decline were consistent with an objective characterisation of decline based on in-field measurements of the indicators. Although vine mortality progressively spread over the years, neither the survey nor the historical analysis showed a direct link between decline and yield loss. Rather, large yearly fluctuations in yield, which did not systematically decrease over time, account for this finding. As a result, the mortality rate and the normalised difference vegetation index (NDVI) indicators were shown to be earlier indicators of grapevine decline than yield loss (yield achievement ratio, YAR). We performed a multifactorial analysis of the overall data set from the three regions to deepen our understanding of the variety of declining situations and the underlying environmental and management factors contributing to decline. Finally, two ground-based NDVI indicators and an image-analysis methodology using aerial photographs were proposed as easy-to-obtain indicators of grapevine decline. NDVI indicators were linearly correlated to both YAR and mortality rate. This study provides a better understanding and promising tools for early diagnosis of grapevine decline.