Tracking the source of aphid-vectored virus in winter wheat

Kentucky soft red winter wheat, Triticum aestivum L., is the fourth most valuable crop in the state, behind tobacco, corn and soybeans (Lee et al. 2009). Average yield across the state is increasing due to improved varieties and more intense management practices, while, however, the total number of acres planted is decreasing. Western Kentucky is the major winter wheat growing region in the state, with an annual yield of $180 million, and in order to maintain this profit it is essential to identify sustainable management practices. Through increased knowledge of our crops, it may be able to achieve these goals. One of the factors affecting winter wheat yield is Barley Yellow Dwarf virus (BYDV), affecting 17% of Kentucky's wheat resulting is an annual loss of $30 million. Aphids (Hemiptera: Aphididae) are the vectors of Barley Yellow Dwarf virus (BYDV), and through feeding, transmit it to plants. BYDV is the most widespread and harmful plant disease in the world (Sadras et al. 1999), causing infected plants to become stunted and discolored (D'Arcy 1995). At harvest time, plants with the virus have lower fertile head densities, kernel weights and test weight. In Kentucky, the most important time of BYDV infection occurs in the fall but its symptoms usually appear in the spring and summer (Hershman and Johnson 2009). The aphids responsible for virus transmission in this region include five species; English grain aphid (Sitobian avenae F.), bird-cherry oat aphid (Rhopalosiphum padi L.), greenbug (Schizaphis graminum Rondani), corn leaf aphid (Rhopalosiphum maidis Fitch) and rice-root aphid (Rhopalosiphum rufiabdomainalis (Sasaki). Understanding the movement of both and aphids and the virus into this system from the surrounding environment is therefore important when developing an effective control program for BYDV in Kentucky wheat. This project will therefore provide detailed temporal and spatial information on the aphid species, including their distribution and abundance, which vector BYDV, allowing growers to make more informed management decisions. Due to the cyclical nature of pest and predator populations, to encompass temporal as well as spatial aspects to the research, two years of funding is requested. Additionally, we anticipate using this funding, if received, to generate sufficient data to leverage support for Kentucky wheat research from Federal (e.g., USDA) funding agencies. This project seeks funding to support a second year of research in a two-year study in Kentucky winter wheat. Extensive research conducted during Year 1 includes 180 aphid traps, each set out for 24 hours, on four different fields at the University of Kentucky Research and Education Center. Each aphid trap designed by this research project was successful at catching alate aphids traveling to and from the crop, as well as a diverse group of other insects. Traps were used in fields that had bordering weed strips as a conservation biological control strategy, and fields that had no manipulation. The traps are currently being analyzed, with all of the aphids being identified to species level, and all other arthropods being identified to family level. An additional 1,200 aphids were collected from the winter wheat fields to be screened for the virus. Using a previously optimized technique, an enzyme linked immunosorbent assay (ELISA) will be used to test the aphids for BYDV.