COS 10-7
Organic and conventional farming practices: Diversity and effects on natural enemies at different spatial scales

Monday, August 11, 2014: 3:40 PM
Regency Blrm E, Hyatt Regency Hotel
Camille Puech, INRA UR 980, SAD-Paysage, Rennes, France
Jacques Baudry, INRA UR 980, SAD-Paysage, Rennes, France
St├ęphanie Aviron, INRA UR 980, SAD-Paysage, Rennes, France

Due to the use of alternative practices, Organic Farming (OF) is considered a promising type of production to insure food security and biodiversity conservation. In particular, biological control of pests by their natural enemies is examined as a possible way to reduce pesticide use. Studies investigating the effects of farming practices on natural enemies are contradictory. Most of them include neither the diversity of practices existing within OF and Conventional Farming (CF), nor the surrounding landscape characteristics. The aim of this work is to describe the diversity of practices in organic and conventional mixed crop-livestock farms and to identify the spatial scale at which farming practices are the most effective at enhancing arthropods natural enemies populations. Twenty 1km² landscapes were selected in western France, characterized by varying surface areas of OF. In each landscape, aphids natural enemies communities were sampled in 2012 and 2013 in two winter wheat fields, one organic and one conventional. Detailed agricultural practices of sampled and surrounding fields were collected. Landscape descriptors were calculated in nested buffers around each field, in order to describe the composition (% of each farming strategy) and the spatial organization (aggregation index) of farming practices at different spatial scales.


The results showed that both farmers under OF and CF implement a diversity of farming strategies, although the dichotomy between the two production types remained well marked. We observed this trend both in sampled winter wheat fields and in surrounding crops, questioning the relevance of the usual dichotomy. Overall, organic practices seemed to be more favorable to the presence of beneficial insects than conventional practices, due to the lack of pesticides and to a more favorable microclimate (dense and diversified vegetation) in fields. Natural enemies were mainly affected by farming practices implemented in the field and in the nearby surrounding landscape (composition in a range of 50m). Their abundance was greater in organic fields surrounded by high surface areas of OF. However, the spatial organization of farming practices had no effect on them, suggesting that biological control can potentially occur in landscapes where organic fields are not aggregated. These results give trails for the management of agro-ecosystems, especially for the development of organic farming and the improvement of biological control in hedgerow network landscapes.