Field and Landscape Risk Factors Impacting Flavescence Dorée Infection: Insights from Spatial Bayesian Modeling in the Bordeaux Vineyards.

Flavescence dorée (FD) is a quarantine disease threatening European vineyards. Its management is based on mandatory insecticide treatments and the uprooting of infected plants identified during annual surveys. Field surveys are currently not optimized because the drivers affecting FD spread in vineyard landscapes remain poorly understood. We collated a georeferenced dataset of FD detection, collected from 34,581 vineyard plots over 5 years in the South West France wine region. Spatial models fitted with integrated nested Laplace approximation were used to identify local and landscape factors affecting FD detection and infection. Our analysis highlights the importance of sampling period on FD detection and of local practices and landscape context on FD infection. At field scale, altitude and cultivar choice were the main factors affecting FD infection. In particular, the odds ratio of FD infection in fields planted with the susceptible Cabernet Sauvignon, Cabernet Franc, or Muscadelle varieties were approximately twice those in fields planted with the less susceptible Merlot. Field infection was also affected by the field's immediate surroundings (within a circle with a radius of 150 to 200 m), corresponding to landscapes of 7 to 12 ha. In particular, the probability of FD infection increased with the proportions of forest and urban land and with the proportion of susceptible cultivars, demonstrating that the cultivar composition impacts FD epidemiology at landscape scale. The satisfactory predictive performance of the model for identifying districts with a prevalence of FD detection >10% of the fields suggests that it could be used to target areas in which future surveys would be most valuable.

Efficiency and equity in land conservation: the effects of policy scale.

This paper studies the effects of policy scale for land conservation schemes based on global objectives but implemented at local levels. They are explored in the classical reserve site selection framework for policy efficiency, to which we add the common social objective of equity between spatial units. We first analyze the role of the biophysical attributes of land available for conservation. These natural endowments are then combined with different implementation scales to improve a particular land-based social function: natural habitats for biodiversity. An empirical illustration, based on data from the Provence region of France, is used to explore what we identify as a policy scale trade-off between administrative units. This shows the importance of land availability in predicting the distribution of the costs and benefits of conservation schemes. In terms of equity, we find an interior solution that minimizes an inequality metric (the Gini coefficient) along policy scales. Our approach should lead to more socially acceptable conservation objectives, between the usual two extreme cases of autarky and specialization.