NONTARGET INSECTS IN UNSPRAYED CEREAL EDGES AND APHID DISPERSAL TO THE ADJACENT CROP

In 1992 and 1993 6 m wide edges of a winter wheat crop were not spraye d with herbicides and insecticides to investigate the impact on the ab undance of insects inhabiting the upper parts of the crop and on farml and flowers. To this end, a total of 19 fields were sampled using swee p nets. It was demonstrated that the number of insect groups as well a s 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 studie d, too, a significant increase in numbers was found for most groups. T his held true for aphid predators (mainly Coccinellidae), flower visit ors (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 ed ges with farm management.