Agroecological infrastructures to enhance the presence of natural enemies against aphids

The effect of agroecological infrastructures has been tested on Aphis gossypii Glover-melon pathosystem. During a three-year project in southern France, flower strips have been sown around melon crops with species known to attract natural enemies, and compared to a bare soil control. The development of the flower strips, the transfer of beneficials from the surroundings into the crop, the colonisation of natural enemies in the plot, and the reduction of aphids outbreaks were investigated. The trial, located on an organic commercial farm, showed that flower strips have to be carefully set up, in terms of irrigation and soil tillage, to ensure an optimal growth and floral diversity in the strips. Regarding arthropods population, it appeared that flower strips significantly increased the transfer of predators towards the crop (among them generalist ones as Carabidae and Forficulidae), but also specific enemies against aphids (especially Syrphidae and Coccinellidae). In the melon crop, specific enemies against aphids (especially Coccinellidae) established on larger number in the "strip" plot, with a significant effect. At the same time, aphids outbreaks were not significantly different between the control plot and the "strip" plot.