Weed hosts: hidden reservoirs for whitefly-transmitted viruses threatening Georgia cucurbits

Authors: DHADLY, DALVIR - University Of Georgia; KAVALAPPARA, SARITHA - University Of Georgia; MCAVOY, THEODORE - University Of Georgia; SEVERNS, PAUL - University Of Georgia; Simmons, Alvin; SRINIVASAN, RAJAGOPALBABU - University Of Georgia; BAG, SUDEEP - University Of Georgia

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2025
Publication Date: 3/27/2025
Citation: Dhadly, D.K., Kavalappara, S.R., Mcavoy, T., Severns, P.M., Simmons, A.M., Srinivasan, R., Bag, S. 2025. Weed hosts: hidden reservoirs for whitefly-transmitted viruses threatening Georgia cucurbits. Plant Disease. https://doi.org/10.1094/PDIS-12-24-2730-RE.
DOI: https://doi.org/10.1094/PDIS-12-24-2730-RE

Interpretive Summary: Weeds on farms are a big problem because they harbor plant diseases, and insect pests can move the diseases into crops. The cucurbit leaf crumple virus (CuLCrV) and cucurbit chlorotic yellows virus (CCYV) are whitefly-transmitted viruses that cause severe losses in cucurbit crops in the southeast US. This study identified weeds in the field infected by CuLCrV and CCYV and determined that they can serve as a source of sustaining viruses in and around fields year-round. Cypressvine morningglory (Ipomoea quamoclit), tall morningglory (Ipomoea purpurea), pigweed (Amaranthus sp.), and wild radish (Raphanus raphanistrum) were found to harbor both viruses as mixed infections of CCYV and CuLCrV in the field. Single-virus infections of CuLCrV were detected in lantana (Lantana camara), and single CCYV infections were identified in prickly sida (Sida spinosa). Whiteflies sucked up and transmitted these viruses from the weeds to yellow squash. Because whiteflies feed and breed on these weeds, the plants can be an important reservoir for these viruses. The results of this study will be useful for scientists and agricultural practitioners to develop improved management strategies against these diseases in cucurbit production systems.

Technical Abstract: Weeds play a crucial role in plant disease dynamics by serving as reservoirs for pathogens and vectors, complicating disease management and facilitating year-round pathogen survival. In the southeastern United States, whitefly-transmitted viruses such as cucurbit leaf crumple virus (CuLCrV) and cucurbit chlorotic yellows virus (CCYV) cause severe losses in cucurbit crops. This study identified weeds infected by CuLCrV and CCYV in the field conditions and evaluated their potential to serve as virus reservoirs in Georgia, USA through greenhouse experiments. Cypressvine morningglory (Ipomoea quamoclit), tall morningglory (Ipomoea purpurea), pigweed (Amaranthus sp.), and wild radish (Raphanus raphanistrum) were found to harbor both viruses as mixed infections in the field. Single-virus infections of CuLCrV were detected in lantana (Lantana camara), while CCYV infections were identified in prickly sida (Sida spinosa). Detection of these viruses in weeds during pre- and post-cucurbit cropping periods suggests their role in sustaining virus populations year-round. Although CCYV titers in weed hosts were low, whiteflies acquired the virus from infected weeds and transmitted it to yellow squash (Cucurbita pepo), which developed typical CCYV symptoms. Whiteflies also acquired and transmitted CuLCrV from weeds to yellow squash; however, despite the presence of replicative forms of CuLCrV in yellow squash, the plants remained asymptomatic for unknown reasons. These weeds are also suitable feeding and breeding hosts for whiteflies, thus making them effective reservoir hosts for viruses in the region. By identifying key weed species that serve as virus reservoirs, this study provides essential insights for developing integrated disease management strategies in cucurbit production systems.