The Role of Henosepilachna vigintioctopunctata in Facilitating the Spread of Tomato Brown Rugose Fruit Virus (ToBRFV) Among Hosts

Tomato brown rugose fruit virus (ToBRFV), a highly stable and mechanically transmissible tobamovirus, poses a significant threat to solanaceous crops worldwide, particularly tomato (<i>Solanum lycopersicum</i>). While its transmission via human activities and contaminated materials is well-documented, the role of common phytophagous insects in its epidemiology remains less understood. <i>Henosepilachna vigintioctopunctata</i>, the Hadda beetle, is a common pest of Solanaceae with a host range that overlaps extensively with that of ToBRFV. This study aimed to quantify the beetle's capacity to act as a mechanical vector and to assess its potential epidemiological impact. Using reverse transcription quantitative PCR (RT-qPCR), we evaluated beetle-mediated transmission efficiency, the persistence of its virus-carrying capacity, and its ability to vector the virus to various solanaceous hosts. Our results demonstrate that <i>H. vigintioctopunctata</i> efficiently acquires and transmits ToBRFV to tomato and other key hosts, including black nightshade (<i>S. nigrum</i>), pepper (<i>Capsicum annuum</i>), and eggplant (<i>Solanum melongena</i>). The virus was retained and remained transmissible by beetles for up to 48 h post-acquisition, providing a significant window for dispersal. Viral particles were most abundant in the digestive tract, consistent with ingestion of infected tissue, and declined rapidly on external body parts, confirming a non-circulative, mechanical transmission mechanism. Furthermore, feeding wounds created by non-viruliferous beetles increased plant susceptibility to subsequent infection from environmental contamination. We conclude that <i>H. vigintioctopunctata</i> acts as a potential mechanical vector that might amplify ToBRFV spread at local and landscape levels. This highlights a synergistic interaction between a native pest and an invasive pathogen, underscoring the necessity of incorporating beetle management into integrated strategies for controlling ToBRFV.