The potential of leys and short rotation coppice hedges as reservoirs for parasitoids of cereal aphids in organic agriculture

Abstract

The aim of this study was to assess whether leys used for nitrogen fixation and fodder, which cover from a fifth to more than half the acreage on organic farms, as well as short rotation coppice (SRC) used for energy purposes, have potentials as reservoirs for aphid parasitoids in organic agriculture. Exposure of cereal aphids to naturally occurring parasitoids in various crops showed that parasitoids capable of parasitizing the pest aphid Sitobion avenae were active in ley, alfalfa and SRC from spring to late autumn, but in barley fields only in mid-summer. Parasitism by Aphidius sp. dominated in ley, whereas parasitism by Praon sp. was most frequent in SRC. Alternative aphid hosts for parasitoids of S. avenae were shown to be present in late summer, late autumn and early spring in ley and SRC. Within field distribution of parasitism and prevalence of entomophtoralean fungi on aphids in spring barley fields were determined by spatially explicit sampling, but was not consistently affected by proximity to ley or SRC. The data indicate that SRC hedges and clover/grass leys in the rotation may increase diversity and activity of parasitoids attacking cereal aphids.