Habitat manipulation to promote sustainable management of viruliferous aphids

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 and Sitobion avenae) cause substantial yield loss as vectors of Barley Yellow Dwarf virus (BYDV), prompting the routine application of insecticides.  Importantly, these aphids are preyed upon by foliage dwelling predators and, when they fall to the ground, epigeal species which play a major role in preventing re-colonization of the plant.  Following the theories of conservation biological control, 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, integrating field ecology, molecular ecology and immunoassays, this hypothesis was tested with extensive sampling to collect aphids and natural enemies in wheat.  Specifically designed aerial aphid traps showed that, regardless of the prevailing winds, aphids were consistently moving into the wheat fields from the western and southerly direction.  This pattern is consistent for aphids emigrating from and immigrating into the fields, and is shown both in control fields and fields with bordering weed strips.  Within field movement of aphids, BYDV and natural enemies was analyzed using Spatial Analysis by Distance IndicEs (SADIE), revealing significant spatial and temporal relationships.  These relationships are altered with the addition of weed strips, and the information gathered provides us with the ecological framework we need to make pest management decisions for major agricultural crops.