The influence of landscape on insect pest dynamics: a case study in southeastern France

Managing the spatial distribution of crop and non-crop habitats over landscapes could be used as a means to reduce insect pest densities. In this study, we investigated whether or not landscape characteristics affected the number of codling moths in commercial orchards. To do this, we collected overwintering larvae in 2006 and 2007 in 76 orchards over a 70 km2 area in southeastern France. We analysed variations in the number of larvae using correlation tests and linear models. As independent variables, we took both characteristics of focus orchards (pear vs. apple, organic vs. conventional orchards) and of their surrounding landscape (orchard density and hedgerow network attributes) into account in buffers with widths varying from 50 to 500 m. Although the codling moth is specialised on orchards, the number of codling moths was lower in orchards within a high orchard density area. There was some indication that this effect was mostly due to the density of conventional orchards and thus to the intensity of insecticide treatments. Conversely, we found no particular effect of abandoned or organic orchards. In 2006, the number of codling moths was also significantly lower in a focus orchard when the hedgerow network acted as a protection against the prevailing wind. Finally, major effects of landscape variables on the number of codling moths were observed for distances of less than 150 m from the focus orchards, suggesting that codling moth management should be organised over areas of about 16 ha. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.