Comment favoriser la régulation biologique des insectes de l’échelle de la parcelle à celle du paysage agricole, pour aboutir à des stratégies de protection intégrée sur le colza d’hiver ?

Continuous increases in the use of synthetic fertilisers and pesticides in agro-ecosystems have led to an increase in crop production, but also to a simplification of landscape and a decline in biodiversity at the field, cropping system level. Changes at landscape level, such as regional farm specialisation, increases in field size and the removal of hedgerows and woodlots suppression, have strengthened this tendency towards decline. The loss of biodiversity in agro-ecosystems has increased the need for external inputs, as important functions are no longer provided by beneficial species. This has led to an apparently inevitable reliance on petrochemicals in production systems. However, many scientists are arguing that this reliance on pesticides could be considerably reduced by making better use of biotic interactions. This review explores, in the light of recent studies, possible ways to increase beneficial biotic interactions in agro-ecosystems, and to improve bio control pest management at field and landscape scales. This review also points out the possible integrated cropping system on oilseed rape and concludes on the future research that has to be engaged to achieve the goal of improvement the natural bio-control of pests. For example at field scale, it has been shown that the choice of cultivar, the sowing date and nitrogen fertilisation practices can be manipulated to prevent interactions between pests and crop, in either time or space . We have also highlighted that beneficial biotic interactions may result from appropriate changes to the habitats of beneficial species, mediated by soil management and cover or mixing species utilisation. Finally, changes achieved at landscape scale appear promising. However, these approaches frequently also present drawbacks that may not necessarily be outweighed by the beneficial effects. Endly, we propose the approaches to design integrated crop management systems to reduce the damage of pests. However, major research efforts are required to quantify and to use the effects of management practices and to improve our understanding of the interactions between the different levels.