Spatiotemporal distribution and prevalence of aphid-vectored yellow dwarf viruses in Oregon grass seed crops

Oregon’s grass seed industry is valued at over $500 million. Perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) are the primary species produced, and both are susceptible to yellow dwarf viruses (YDV) vectored by multiple aphid species. YDV infection of perennial grasses limits yield potential and reduces stand longevity. The composition of YDV strains and aphid species across Oregon’s grass seed production regions are relatively unknown and have not been evaluated with PCR detection methods. Starting in the fall of 2021 and continuing in 2022, over 50 commercial fields have been selected for aphid monitoring and plant sampling, across the Willamette Valley and in central and eastern Oregon. Fields varied in stand age and were selected based on a spatial gradient of crops identified as potential YDV hosts (e.g., corn, wheat). Aphids were counted weekly on yellow sticky cards, and approximately three weeks after peak counts, ten random leaf samples were collected from four 100 m transects per field. Early and late-season collections of alate aphids and plant samples were extracted for total nucleic acids and evaluated for the incidence of YDV strains using multiplex PCR protocols. These data will be used to determine the spatiotemporal distribution of YDV and aphid species in Oregon perirenal grass seed systems, variation in disease incidence within fields, as well as management and local environmental risk factors associated with disease outbreaks. This work will inform integrated pest management strategies for the aphid and YDV virus-vector complex in Oregon.