As fruits are delicate high value products and orchards perennial systems, they easily support the installation of windbreaks in windy regions. The most common ones are planted hedgerows. Some of the planted hedgerows in the orchard boundaries are multi-species hedgerows, for instance, composed after the recommendations by the IDF (Institut pour le Développement Forestier, 1981). As the diversity of planted fruit species or cultivars is low within the orchards, e.g. the most common cases are one or a few clones, these hedgerows improve the orchard system plant diversity. Although hedgerows may impair crop protection by harbouring potential pests and diseases, they are also physical barriers that stop drifts from adjacent pesticide applications and thus minimise side effects of pesticide use. If the hedgerow contributes by itself to the local plant biodiversity through the same mechanisms as plant covers, the association of orchards and hedgerows within the landscape creates and favours specific habitats and ecosystems. This contributes to the increase in global and landscape biodiversity (Pollard and Holland, 2006). A mosaic landscape consisting of orchards separated by hedgerows and/or ditches favours a specific flora and fauna through a higher availability
of habitats and resources. Such areas are also hibernating sites for many insect species. The communities of both adjacent plantings and local surroundings interfere with the orchard. On a local scale, the biodiversity of the orchard system is improved by lining hedgerows and ditches, as the biodiversity on the landscape scale is improved through an
increase in available biotopes. This latter aspect is especially emphasised for mobile taxa such as Lepidoptera and birds. Orchard systems and their boundaries are thus highly relevant candidates to contribute plant and animal diversity on
different scales.
However, it is necessary to minimise such potentially favourable situations: the widespread use of the mating dis-
ruption method to control Lepidoptera requires large surface areas without interplanted hedgerows. Italian and Northern American studies indicate an optimal efficiency for continuous surface areas of homogeneous orchards of tens of hectares
protected by this method, which favours pheromone diffusion and minimises the vulnerability of borders. A recent study
(Ricci et al., 2009) also indicates that the codling moth Cydia pomonella populations of a given orchard are negatively
correlated with the surrounding surface areas planted with apple and treated with chemicals, which promote the production of apples within large surface areas whatever the pest control method (if efficient) against codling moth. The planting of large surface area orchards excluding hedgerows, which are replaced by hail nets as windbreaks and shields for the physical control of C. pomonella and tortricids, are likely to develop in Southern France. There is an antagonism between the optimal use of various pest control methods and the management of plant diversity in the boundaries of the
orchard system.