D3514: Survey of weeds as reservoirs of whitefly-transmitted viruses impacting melon crops in Yuma, AZ

Arizona’s leafy greens and melon industries contribute more than $2.5 billion to the state’s economy. The Sweet potato whitefly (Bemicia tabaci) transmitted disease Cucurbit Yellow Stunting Disorder Virus (CYSDV) is a significant threat to melon (Cucumis melo) production in the state. Weeds play an integral role in supporting whitefly populations and in the occurrence of melon viruses. CYSDV has severely impacted melon production by reducing yield and fruit sugar content in Yuma, AZ since 2006. In recent seasons, another crinivirus, cucurbit chlorotic yellows virus (CCYV), and the whitefly-transmitted ipomovirus, squash vein yellowing virus (SqVYV) have been found infecting melon plants in the US desert southwest. Melon plants may have mixed infections of CYSDV, CCYV, and an aphid-transmitted polerovirus, cucurbit aphid-borne yellows virus (CABYV). All these viruses occur together in the region and produce identical yellowing symptoms on cucurbit plants, making disease management and efforts to develop cucurbit-resistant varieties more difficult. Additionally, several weed species can serve as reservoirs for whiteflies and whitefly-transmitted viruses, allowing viruses to persist in the environment when melons are not produced. The purpose of this project is to identify the most important weed hosts of these four viruses in Arizona. Over 1000 weed and whitefly samples have been tested for virus presence using RT-qPCR. Weeds commonly found in the growing region have been identified as hosts of these viruses, including new hosts. Results from this project help inform management recommendations for whitefly-transmitted viruses, including weed control and measures to reduce virus incidence across agroecosystems.