1st Place: Spatial and temporal analysis of iris yellow spot virus (IYSV; Peribunyaviridae) in New York onion fields

Iris yellow spot virus (IYSV) is an economically significant tospovirus in the family Peribunyaviridae, and is transmitted by onion thrips, Thrips tabaci Lindeman. IYSV reduces overall quality and marketable bulb weight up to 50%. IYSV can be detected in many onion fields across New York, but its incidence and severity have increased dramatically in western New York over the past several years. Early in the season, IYSV epidemics originate from transplanted onion fields rather than direct-seeded fields. Therefore, we hypothesized that onion thrips populations would colonize transplanted fields and the incidence of IYS disease would be highest in these transplanted fields early in the season. As the season progressed, we hypothesized that onion thrips populations would disperse to adjacent direct-seeded fields followed by increased rates of IYSV. In 2021, populations of onion thrips and IYSV were surveyed in 12 onion fields (4 transplanted fields, and 8 direct-seeded fields), four times throughout the growing season (n=48 samples), and a spatial and temporal analysis was conducted to determine the patterns associated with onion thrips dispersal between direct-seeded and transplanted onion fields, and the epidemiological patterns of IYSV. Results indicated that both onion thrips and IYSV were encountered equally in both field types early in the season, suggesting a lack of predominance in transplanted fields. These results indicate the need for further evaluation of onion thrips overwintering emergence, subsequent dispersal and viruliferous status to understand the factors that drive IYSV epidemics in onion producing regions in New York.