Weed Hosts: Hidden Reservoirs for Whitefly-Transmitted Viruses Threatening Georgia Cucurbits

The presence of weeds can undermine effective crop disease management when their role as functional reservoirs for pathogens and/or vectors is unrecognized. Weed presence and abundance cannot only influence disease dynamics during the growing season but also enable year-round pathogen presence, facilitating recurrent and persistent disease outbreaks. Cucurbit leaf crumple virus (CuLCrV) and cucurbit chlorotic yellows virus (CCYV) are whitefly-transmitted viruses (WTVs) that cause severe losses in cucurbit crops in the southeastern United States. We evaluated the potential for weeds found on the margins of cucurbit fields to be reservoirs for CuLCrV and CCYV through a combination of field sampling, molecular detection, and greenhouse transmission experiments with infected weeds and uninfected recipient yellow squash (<i>Cucurbita pepo</i> cv. Gold Star). Field-collected cypressvine morning glory (<i>Ipomoea quamoclit</i>), tall morning glory (<i>Ipomoea purpurea</i>), pigweed (<i>Amaranthus</i> sp.), and wild radish (<i>Raphanus raphanistrum</i>) were found to harbor both viruses as mixed infections. Single-virus infections of CuLCrV and CCYV were detected in field-collected lantana (<i>Lantana camara</i>) and prickly sida (<i>Sida spinosa</i>), respectively. Although virus copies in weed hosts were low during greenhouse transmission studies, whiteflies successfully acquired these viruses from infected weeds and transmitted them to previously uninfected yellow squash. CCYV-inoculated yellow squash developed typical symptoms, whereas CuLCrV-inoculated squash remained asymptomatic despite the presence of replicative virus forms. Because the weeds identified in this study are also known to be suitable hosts for whiteflies, they could be considered as potential targets for integrated pest management strategies.