Barley Yellow Dwarf virus in winter wheat: examining the spatial and temporal movement of its aphid vectors

Aphids are pests of multiple cropping systems, due to the viruses they vector and the staggering populations they can build within a single season. In Kentucky winter wheat, grain aphids (Rhopalosiphum padi, Sitobion avenae) cause substantial yield loss as vectors of Barley Yellow Dwarf virus (BYDV), prompting multiple insecticide applications. They transfer the virus from infected to healthy plants as they feed, causing discoloration, stunted growth and sterility. 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 help suppress pestiferous aphid populations. Using a variety of techniques, this hypothesis was tested with extensive sampling to collect plants, aphids and natural enemies in wheat. In the laboratory, samples were indentified and screened for BYDV using enzyme linked immunosorbent assay (ELISA) to quantify the level of infection in the field. To examine the spatial and temporal movement of BYDV's aphid vectors over the winter wheat season, as well as their natural enemies, Spatial Analysis by Distance IndicEs (SADIE) was used to look at the aggregative properties of these populations and any relationships between them. Results will be discussed in the context of conservation biological control, and how low-cost, low-input manipulations may impact viruliferous aphid populations.