Ecosystem services for the control of Bactrocera oleae in different landscape spatial contexts
Abstract: Landscape structure can affect pest populations directly or indirectly through its effect on natural enemies of the pest and the ecosystem services provided, i.e. parasitism and predation. Rates of parasitism and predation on the olive fruit fly, Bactrocera oleae, were measured in different landscape spatial contexts trying to elucidate the mechanisms responsible for previously reported lower densities of the insect associated with complex landscapes. The study was carried out in Madrid in autumn 2014, using 15 olive groves in a gradient of landscape complexity. Parasitism rates found were very low for Psyttalia concolor (0-3.13%) and negligible for Pnigalio mediterraneus (0-0.86%). Values of a biocontrol service index (BSI) indicating intensity of predation ranged from 0 to 0.63. Landscape structure was characterized at four spatial scales: circular areas of 500, 750, 1000 and 1500 m radii around the olive groves. Neither parasitism nor predation showed a significant relationship with any of the calculated landscape indices (number of patches, mean patch size, total length of patch edges and Shannon diversity index). This suggests a direct effect of landscape structure on B. oleae, but other hypotheses are discussed in the context of conservation biological control.