Authors: Rodenwald, Nathalie; Leuschner, Christoph;Batáry, Péter;

The recent decline of semi-natural habitats in European agricultural landscapes has led to a tremendous biodiversity loss. A widespread tool to halt any further decline are agri-environmental measures such as flower strips. To date, the potential beneficial effect of flower strips on ecosystem services such as biocontrol has predominantly been studied in organic farmland, even though the majority of agricultural land is farmed conventionally. We investigated the potential of perennial flower strips (compared to grassy field margins) to enhance spill-over of natural enemies into adjacent conventionally-managed cereal fields. We used cereal tiller counts and D-Vac sampling to quantify aphids, cereal leaf beetles and their natural enemies at increasing distances from each habitat type.

Our results suggest a contrasting effect of habitat type on the two investigated pest species at peak infestation point. However, the ratio of enemies to pest individuals tends to be slightly higher with adjacent flower strips compared to grass strips for both pest species.

We conclude that perennial flower strips have weak beneficial effects on biocontrol at peak infestation, even in conventionally-managed agricultural systems. This effect may vary during the course of infestation. Therefore, we propose that future investigations consider temporal pest-enemy dynamics.