Landscape context affects parasitism of aphids in wheat fields by Lysephlebus testaceipes

We investigated parasitism by Lysephebus testaceipes on bird-cherry oat aphids in the field.  We conducted study in central Oklahoma in 24 wheat fields selected to span a range of landscape context, ranging from fields surrounded by primarily cultivated agricultural crops to field surrounded primarily by semi-natural habitats.  In these fields we deployed sentinel plants to estimate levels of parasitism and also sampled the fields with a suction sampler to determine cereal aphid and natural enemy abundance.  Data were collected on percent of sentinel plants with parasitized aphids and numbers of parasitized aphids per plant.  In addition, we determined cereal aphid and natural enemy abundance in the suction samples.  Regression analyses indicated that landscape context had a significant effect on parasitism rates by L. testaceipes.  Results are discussed in terms of the magnitude and spatial extent of landscape effects on parasitism.