Potential insect vectors of citrus yellow vein clearing virus in Southern California

Citrus yellow vein clearing virus (CYVCV) is an emerging viral pathogen of citrus recently detected in California. While the virus is known to spread through infected budwood and mechanical contact, its potential insect vectors remain unconfirmed. CYVCV belongs to the Mandarivirus subgenus (Alphaflexiviridae) and has a broad host range, including citrus, herbaceous plants, and several weed species, raising concerns about its spread and persistence in diverse environments. To explore possible vector involvement, we conducted surveys in citrus-growing regions of Southern California, targeting symptomatic citrus trees, surrounding weed hosts, and phloem-feeding insects such as aphids and whiteflies. Molecular testing (RT-PCR) detected CYVCV in both aphids and whiteflies collected from multiple field sites. Additionally, mechanical inoculation trials under greenhouse conditions successfully transmitted the virus to healthy lemon plants, which developed vein clearing symptoms within two months. We further confirmed CYVCV identity through full-genome sequencing of viral RNA isolated from infected plants and insect vectors. While mechanical transmission is clearly possible, the consistent detection of CYVCV in field-collected aphids and whiteflies suggests a potential role in virus acquisition and movement. These findings highlight the importance of insect vectors in the ecology of CYVCV and raise new questions about how climate, plant community shifts, and vector populations may shape virus spread. Continued research will be critical for understanding CYVCV transmission dynamics and for developing integrated management strategies to protect citrus in a changing environment.