Management of field margins to maximize multiple ecological services.
Vegetative buffers in agricultural landscapes can provide a range of important ecological services, including conservation of native flora and fauna, enhancement of biological pest control and reduction of agrochemical drift. Typically, studies addressing the impact of such vegetative elements focus on one particular been fit. Field studies were conducted in Georgia, USA, to determine whether the benefits of field margins that had been established for conservation of northern bobwhite quail Colinus virginianus populations extended to the enhancement of biological pest control in adjacent conservation tillage cotton fields. Densities of a selection of insect species and the predation and parasitism rates of insect pest species were measured in first- and second-year field margins established for bobwhite quail and in an adjacent cotton crop. Second-year field margins yielded higher densities of all species sampled, with the exception of staphylinids and cotton aphids. Despite this, thrips and their predator, Orius insidiosus, were the only species that were also more abundant in the adjacent cotton field. Tachinids and Trichogramma and Lygus species appeared to prefer the field margin vegetation over the cotton. Overall, the impact of second-year margins on the cotton crop did not significantly differ from first-year margins with regard to pest occurrence or biological control. Analysis of the sugar content in Meteorus autographae, a generalist parasitoid of Lepidoptera larvae, suggested that this species is severely food-limited in the field margins established for bobwhite quail. Results showed that field margins designed to specifically benefit bobwhite quail may be unsuitable for providing other ecological services. By making small adjustments in the vegetative composition of these field margins, such as adding early season nectar-producing plants, it may be feasible to combine biodiversity and pest control benefits and thereby optimize the overall ecological services to be gained.