15: Emergence, epidemiology and ecology of whitefly-transmitted cucurbit viruses in the southwestern United States

An increasing number of whitefly transmitted viruses have impacted cucurbit production in the southwestern United States since the emergence of Bemisia tabaci MEAM1 in the early 1990s.  The most impactful of these has been cucurbit yellow stunting disorder virus (CYSDV), which was first identified in 2006 and reduces sugar in fruit.  Efforts to manage CYSDV led to extensive studies to determine the host range and regional epidemiology of the virus, and has resulted in advancement of CYSDV-resistant melon lines.  However, two additional whitefly-transmitted viruses, cucurbit chlorotic yellows virus (CCYV) and squash vein yellowing virus (SqVYV) emerged in 2014 and have complicated study and virus management in the southwestern desert production region as well as the ability to evaluate melon plants for virus resistance.  New methods were developed for differential detection of these viruses that allow single reaction differentiation and titer determination for all three viruses and cucurbit aphid-borne yellows virus (CABYV), which produces similar symptoms and is also present in the region.  Studies are examining competitive dominance of viruses in in spring and fall melon seasons and how competition is impacting transmission.