Spill-over of pest control and pollination services into arable crops

In order to make agriculture more sustainable it is important to enhance the natural processes supporting crop production, including pollination and pest control. The distance over which these services are delivered into the crop (referred to as spill-over) sets limitations on biodiversity mediated agriculture sustainability. We assess how pest control of aphids on wheat (Rhopalosiphum padi) and pollinator linked yield gain in oilseed rape decline with distance from the crop edge. For natural pest control we also assess how field margin floristic diversity (simple grass vs. species-rich wildflower) affects pest control. We do not consider the impact of field margins on oilseed rape pollination as perennial dominated field margins are not in flower at the time of oilseed rape seed set and so do not act to attract pollinators. Aphid colonies exposed to invertebrate natural enemies went extinct at a faster rate than colonies where they were excluded. The rate of decline in per capita growth rates of aphid colonies was greatest when exposed to natural predators, with this effect being detected up to 50 m into the crop where species-rich field margins were present. While oilseed rape yield gains were correlated with pollinator (bees and flies) visitation rates, there was no evidence that yield gain declined with distance from the crop edge. Possibly this was due to honeybees showing no evidence of declining visitation rates with distance into the crop (over 200 m). This contrast with bumblebees, solitary bees and flies which showed evidence of declining visitation rates with distance from the crop edge. Our results suggests that for a typical arable field (c. 12 ha) surrounded by species rich field margins, 50% of the total area could benefit from enhanced pest control services. Increased yields of oilseed rape due to insect pollinators of c. 0.4 t ha−1 were identified, but there was no evidence that field size would limit the spatial distribution of yields. Our results have implications for integrated crop management world-wide through the use of variable dose rate applications technologies that could be used to target pesticides to field centres and so help support biodiversity mediated ecosystem services.