Characterisation of predators and/or parasitoids of flies of the genus Delia in brassica crops, and the influence of field margins on natural control processes

The influence of plot margins on the natural regulation of fly populations of the genus Delia in brassica crops was investigated as part of the Biodivleg project by comparing various biological and agronomic variables between plots bordered by semi-natural habitats-natural habitats of high and low density. The results show that the impact of certain species of rove beetles and ground beetles on these flies is significant but that, under the production conditions of the sampled plots, this remains insufficient to significantly limit the extent of damage to the crop. The effect of this predation could, however, be enhanced by establishing high-density semi-natural habitats along the edges of crops, provided that certain cultivation practices are adapted in parallel.