Non-target insects in unsprayed cereal edges and aphid dispersal to the adjacent crop


Centre of Environmental Science, Leiden University, PO Box 9518, 2300 RA Leiden, The Netherlands


Abstract: In 1992 and 1993 6 m wide edges of a winter wheat crop were not sprayed with herbicides and insecticides to investigate the impact on the abundance of insects inhabiting the upper parts of the crop and on farmland flowers. To this end, a total of 19 fields were sampled using sweep nets. It was demonstrated that the number of insect groups as well as the insect density increases in the unsprayed edges, by a factor of 1.4 and 3.5, respectively. At the level of the 21 insect groups studied, too, a significant increase in numbers was found for most groups. This held true for aphid predators (mainly Coccinellidae), flower visitors (mainly adult Syrphidae) and insects that form the staple diet of the bird species Motacilla flava flava. Although there was an increase in aphid abundance in most unsprayed edges, the aphids did not spread to the rest of the field, improving the compatibility of unsprayed edges with farm management.