Biological control in Kentucky winter wheat: using molecular tools to create sustainable management techniques

Aphids are pests of multiple cropping systems, due to the viruses they vector and their rapid rate of population growth. In Kentucky winter wheat, grain aphids (Rhopalosiphum padi, Sitobion avenae) cause substantial yield loss as vectors of Barley Yellow Dwarf virus (BYDV), prompting routine insecticide applications to be applied.  Importantly, these aphids are preyed upon by foliage dwelling predators and, when they fall to the ground, epigeal spiders which play a major role in preventing re-colonization of the plant.  Consequently, natural weed strips were created to increase natural enemy abundance in the wheat, with the hypothesis that they will promote natural suppression of pestiferous aphid populations.  In a multi-faceted approach using spatial, temporal and molecular analysis of predation, this hypothesis was tested with extensive field sampling.  Techniques used include hand collecting of aphids, spiders, predators and plants, sweep netting, micro-sticky traps, and specially designed aphid sticky traps.  In the laboratory, samples were indentified and screened for BYDV using enzyme linked immunosorbent assay to quantify the level of infection in the field.  Additionally, species richness and diversity counts were conducted to examine the effect that natural weed strips may have on the existing arthropod populations.  Results will be discussed in the context of conservation biological control, and how low-cost, low-input manipulations may impact viruliferous aphid populations.