Submitted to: Journal of Applied Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/6/2006
Publication Date: 12/22/2006
Citation: Olson, D.M., Wackers, F.L. 2007. Management of field margins to maximize multiple ecological services. Journal of Applied Ecology. 44(1):13-21. Interpretive Summary: Non-crop vegetative buffers sown within or around crop fields are increasingly recognized for their potential as reservoirs of beneficial arthropod species for biological control of pests in adjacent crops. We investigated whether benefits of field margins that had been established for conservation of Bob White Quail populations extend to the enhancement of biological pest control in adjacent cotton fields. Select insect species were sampled and predation and parasitism rates established for pest species in a cotton crop as well as in adjacent first and second year field Bob White Quail set-asides. Second year margins yielded higher densities of all species sampled except for one predator species and one pest species. Another pest species and one of their predators were the only species that were also more abundant in the adjacent cotton field. Overall, the impact of second year margins on the cotton crop did not significantly differ from first year margins with regard to pest levels or levels of biological control. Three insect species appeared to prefer the edge vegetation over the cotton. Analysis of the gut contents of beneficial parasitoid species collected early in the year suggested that this species is starving in the set-asides, likely because of a lack of a nectar source in the vegetative mix. This study shows that non-crop structures designed for conservation of bird species may be unsuitable for conservation of beneficial insect species. By making small adjustments in the vegetative composition of these structures, we might be able to conserve multiple desired species.
Technical Abstract: We hypothesized that later successional or less frequently disturbed vegetative set asides sown along the edges of crop fields would have greater numbers of insects species because of the availability of resources on a longer-term basis. We also hypothesized that an increase in numbers of the insect species in the vegetative set asides would translate into increased densities in the adjacent crop field. Finally, as the vegetative set asides of interest were sown for the enhancement of Bob White Quail populations, we hypothesized that vegetation selected for quail would not provide needed food in the form of nectar for insects. To test this we analyzed the sugar contents of a beneficial parasitoid species collected from either the quail habitat or from a plot containing the early season nectar producing species, Cahaba White Vetch. We sampled insects in cotton and the set asides from May through mid-September over two years. As expected, we found that 14 out of 16 insect species sampled were more abundant in second versus first year set asides. However, only 2 of the 14 species were also more abundant in the crop field. Parasitism and predation levels of crop pests and insect crop damage did not differ with respect to the set asides. The gut contents of the generalist parasitoid collected in the set asides showed nectar starvation, whereas the gut contents of those collected in the vetch plot had substantial nectar levels. Adding nectar secreting plants to the set asides may increase insect populations thereby providing multiple benefits, such as conservation of quail and beneficial insect species and increased biological control of pests in the crop.