Biodiversity of Agromyzidae (Diptera) in Biologically and Conventionally Grown Spring Barley and Grass Field

ABSTRACTIn southeastern Norway 1998–2000, the number of specimens, species richness and species diversity (measured by Simpsons diversity index) of Agromyzidae were investigated in biologically and conventionally grown spring barley and grass fields. Flies were caught by sweep-net in 1 × 10 m plots in the boundary, 0.5, 5, 15 and 30 m into the fields. A total of 5822 specimens of at least 66 species were caught during the 3 years. The pest species Chromatomyia fuscula(Zett.) and Cerodontha denticornis(Panzer) were most numerous in the fields, while most other species were most numerous in the boundaries. The species richness (for grass only) and species diversity (for cereals and grass) were significantly higher in biological fields, although the pest species (Ce. denticornisand Ch. fuscula) were less abundant in the biologically treated fields. In spring barley fields the species richness and species diversity were significantly reduced when moving from the boundary and into the field. In grass fields this was shown for species richness, but not for species diversity.