THE EFFECTS OF ARTIFICIAL WEED STRIPS ON DIVERSITY AND ABUNDANCE OF THE ARTHROPOD FAUNA IN A SWISS EXPERIMENTAL APPLE ORCHARD

The effects of weed ship management on the diversity and abundance of predators of aphids and their potential alternative prey were studied in a commercial apple orchard in Switzerland. In April 1992, selected weeds were sown in strip form between tree rows and along the border i n one part of the orchard (the other served as a control). In both par ts of the orchard, visual controls and beating tray samples on the app le trees were carried out from March to November in the years 1992 and 1993. At the same time, yellow trap samples and sweep net samples wer e taken in the ryegrass and weed strips. No significant difference in species diversity could be found between the strip-managed area and th e control area, neither for predators of aphids nor for alternative pr ey. However, the strip-managed area was colonised by predators and alt ernative prey in significantly higher numbers than the control. The po ssible factors influencing the effect of the weed strips on predators and on the alternative prey are discussed.