Tracking aphid predation through molecular and spatial analysis

Aphids (Hemiptera:Aphididae) are pests of multiple cropping systems, primarily 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 significant yield loss as vectors of Barley Yellow Dwarf virus (BYDV), prompting the routine application of insecticides.  Coupled with increasing human populations and decreasing arable land, it is becoming increasing evident that biological control services provide by natural enemies represent viable management options.  Aphids are preyed upon by a diverse array of natural enemies in winter wheat and these species can be exploited in conservation biological control.  This research utilized extensive field sampling and molecular techniques to examine spatial and temporal relationships between aphids and their predators.  PCR-based gut content analysis and species-specific aphid primers (R. padi and S. avenae) were used to identify key aphid predators, revealing adult and larval coccinellids (Coleoptera) as the most abundant predators over two field seasons.  Coccinella septempunctata and Coleomegilla maculata were the most prolific aphid predators, but each exhibited a unique feeding habit over the growing season.  Additionally, within field distribution of aphids and coccinellids was examined using Spatial Analysis by Distance IndicEs (SADIE), revealing significant positive associations over the course of the growing season.  C. septempunctata and C. maculata, while utilizing different feeding strategies, should be considered an important part of an integrated pest management program for winter wheat.  The information gathered from this research provides the framework required when making pest management decisions for agricultural crops.