Migrating eastward from previously-infected onion (Allium cepa) fields in the western US, Iris Yellow Spot Virus (IYSV) is a potentially yield-reducing pathogen that was first detected in New York onion fields in 2006. IYSV is a tospovirus transmitted by onion thrips (Thrips tabaci). In order to more fully understand the potential impact of IYSV, it is important to identify and assess the possible sources of the virus. Onion transplants originating from states known to be IYSV-positive are a suspected source, as are volunteer onions, onions left in the field from the previous harvest. To assess the likelihood of either mode of introduction we used DAS-ELISA to test for IYSV in 11 varieties of transplants imported from Arizona, where IYSV is known to occur, and volunteer onions from 9 fields in NY. All transplant samples have tested negative for the virus, while volunteer onions are in the process of being tested and have yet to yield results. Unfortunately, due to the assay’s inherent sensitivity to viral concentration, negative ELISA results cannot be used to completely eliminate the possibility of infection. Only positive results can give us insight into the possibility of either source being a legitimate mode of introduction. The results of these assays will lay the groundwork for future studies on the epidemiology of IYSV, impact on onion crops, and relationship with onion thrips dispersal.