Exploring the factors affecting spatio‐temporal variation in grapevine powdery mildew

Abstract

Context and purpose of the study ‐ The spatial distribution of powdery mildew is often heterogeneous between neighboring plots, with higher disease pressure in certain places that can be considered as disease “hotspots”. The position of hotspots can vary over the years, even if some plots consistently present a higher vulnerability over time. This spatio‐temporal heterogeneity makes it difficult to obtain accurate prediction by epidemiological models that are fed by meteorological variables coming from weather stations that are not in close proximity to the vineyards or are spatialized over large cell grids. The aim of the project was to explore the role of environmental/agronomic factors involved in powdery mildew pressure variation in time and at the plot and regional scale.

Material and methods ‐ To do so, a series of variables were monitored in 10 different vineyards, in the Beaune region (Bourgogne) of France, over two years. These factors included agronomic descriptors and weather variables. Weather data were acquired at the plot scale. Disease symptoms were observed weekly on leaves and grapes, highlighting inter‐plot variation in disease indicators.

Results ‐ The factors that most impacted this variability were relative humidity, rain, leaf wetness, vigor and phenology. A more in‐depth study of the interactions between these factors will help to disentangle the complex effects of the environment on powdery mildew inter‐plot heterogeneity. Relative humidity and leaf wetness appeared as the most closely correlated variables to powdery mildew onset and pressure. Undoubtedly these results need to be further confirmed and quantified through more extended surveys, but they indicate interesting directions for the improvement of predictive models of powdery mildew.